Running head: AGING AND MEMORY FOR TEMPORAL CONTEXT 

Memory for temporal context: Effects of aging, encoding instructions and retrieval strategies

Christine Bastin1 and Martial Van der Linden1,2
1 Department of Cognitive Sciences, University of Liège, Boulevard du Rectorat, B33, B-4000 Liège, Belgium
2 Cognitive Psychopathology Unit, University of Geneva, 40, Boulevard du Pont d’Arve
CH-1211 Genève 4, Switzerland

Abstract

Young and older adults were compared on a list discrimination task. In Experiment 1, performance declined with aging after incidental and intentional encoding of the temporal context. Moreover, there was no benefit for intentional encoding in either group. In Experiment 2, each list was associated with a different encoding context. There were age differences in performance when participants tried to retrieve the encoding context of the items as a cue for their list of occurrence, but not when participants evaluated temporal distance from the strength of the memory trace. This suggests that the age-related decrease in list discrimination could be at least partly due to a difficulty to infer strategically the temporal context of the items from information encoded in the same time.

Memory for temporal context: Effects of aging, encoding instructions and retrieval strategies

	Episodic memory refers to memory for personally experienced events in particular spatial and temporal contexts (Tulving, 1995). The memory trace for such events includes the event itself (content or item) as well as information regarding the conditions under which the event was encountered (source information, including the spatial, temporal and emotional context, Johnson, Hashtroudi, & Lindsay, 1993). It is widely accepted that normal aging adversely affects episodic memory capacities. However, some aspects of episodic memory seem more vulnerable to aging than others. For example, age-related differences are greater on memory for spatio-temporal context than on memory for content (Spencer & Raz, 1995). However, very few studies have explored whether the age-related decline on memory for context is due to a difficulty at the encoding stage or at the retrieval stage. By contrast, the literature on item memory has revealed that both stages may be affected by aging. On one hand, it has been suggested that item memory performance decreases with aging because older adults encode information more poorly than young adults. For example, Perfect and Dasgupta (1997) have demonstrated that the decrease of recollection (remembering an item and its encoding context) in older adults was related to the lack of elaborative encoding. When deep encoding was encouraged, the age difference on recollection disappeared. On the other hand, the retrieval stage in itself can also be affected by aging, especially when it requires effortful retrieval operations. Indeed, some studies that have directly compared recall and recognition memory tasks have shown that age differences were greater for recall than for recognition (Craik & McDowd, 1987; La Voie & Light, 1994; Nyberg et al., 2003; Whiting & Smith, 1997). As recall critically depends on the initiation of retrieval strategies, whereas recognition does to a lesser extent, it has been proposed that aging interferes with active search in memory.
Regarding memory for context, Glisky, Polster and Routhieaux (1995) and Glisky, Rubin and Davidson (2001) have shown that the effect of aging on source memory was related to the degree of frontal dysfunction and that the nature of the difficulty was mainly one of encoding. Glisky et al. (1995) administered to a group of older participants a task assessing memory for the voice (either male or female) speaking a sentence. When the group was divided according to the performance on measures sensitive to frontal lobe dysfunction, participants with low-frontal function performed more poorly on memory for the voice (source) than participants with high-frontal function, but both groups did not differ on memory for the sentence (item). In Glisky et al.’s (2001) study, a similar pattern was observed in a task where the source was the sentence spoken by different voices (Experiment 1) and in a task assessing memory for the room in which different chairs were photographed (Experiment 2). In Experiments 3 and 4, encoding instructions encouraged the integration of item and source information. In Experiment 3, participants had to judge how well a chair fit in a room, whereas in Experiment 4, they had to judge how likely it was that a voice would have spoken a particular sentence. In both experiments, low-frontal function participants performed as well as high-frontal function participants on source memory. This suggests that older adults with reduced frontal lobe function failed to engage spontaneously in an integrative encoding of item and source information. 
In the present experiment, we were interested in memory for temporal context. Different types of temporal information have been distinguished: the duration of events, the relative recency between two events and the position in time of an event among others (Tzeng & Cotton, 1980). Here we focused on the temporal order of events, as assessed by tasks such as recency judgments and list discrimination. Many studies have reported that older adults have more difficulty than younger adults in remembering the time of occurrence of events (Daum, Gräber, Schugens, & Mayes, 1996; Fabiani & Friedman, 1997; Kausler, Salthouse & Saults, 1988; McCormack, 1982, 1984; Naveh-Benjamin, 1990; Newman, Allen, & Kaszniak, 2001; Parkin, Walter, & Hunkin, 1995; Spencer & Raz, 1994; Vakil & Tweedy, 1994; Wegesin, Jacobs, Zubin, Ventura, & Stern, 2000; but see Perlmutter, Metzger, Nezworski & Miller, 1981, for contradictory findings). Particularly, Fabiani and Friedman (1997), Newman et al. (2001), and Parkin et al. (1995) demonstrated a disproportionate decline of memory for temporal context compared to memory for items in older adults. 
Do older participants fail to encode the temporal order of events or does aging interfere with the retrieval of the time of occurrence of items, or both? Few studies examining memory for temporal context in aging have suggested an answer to this question. Spencer and Raz (1994) proposed that, because of age differences on working memory capacities (Salthouse, 1992), older adults might concentrate their diminished resources on the encoding of the events themselves at the expense of contextual information. Recently, an attempt to address this issue has been made by Wegesin, Jacobs, Zubin, Ventura and Stern (2000) who examined the relationships between encoding strategy and list discrimination performance. They presented two lists of words from 4 semantic categories to young and older participants. In one list, words were blocked into their categories, while in the other, categories were intermixed. Recall and recognition of the words were tested, as well as memory for the list. The results indicated greater age differences on temporal context memory than on item recognition. Semantic blocking enhanced item recognition performance in older adults, whereas young adults performed as well on both lists. Spontaneous semantic clustering during recall decreased with aging and correlated with list discrimination performance, suggesting that older participants who developed a semantic clustering strategy remembered better in which list a word was presented compared to those who did not use this strategy. However, it is difficult to say whether these findings provide strong evidence for the idea that an encoding difficulty can explain age-related changes on memory for temporal context. A first reason is that the decline in semantic clustering and list discrimination performance appeared to be related to an age effect on semantic knowledge. Indeed, regression analysis revealed that category fluency and naming significantly predicted semantic clustering and list discrimination scores. Second, performance on the temporal memory task was close to ceiling in young adults and to floor in older participants.
To summarize, little is known about whether age-related differences on memory for temporal context is due to an encoding or a retrieval problem. Therefore, the aim of the present study was to explore this issue. In the first experiment, we tested the hypothesis that age-related difference on temporal context memory is due to a difficulty in older adults to develop strategies at the encoding stage. More specifically, the first experiment examined the role of strategic encoding on memory for temporal context in young and older participants by comparing incidental and intentional encoding of temporal information. In the second experiment, we explored whether the age difference on memory for temporal context may be due to a difficulty at the retrieval stage.
EXPERIMENT 1
	In this experiment, young and older adults performed a list discrimination task following either an intentional or an incidental encoding of temporal context, using faces as material. In the intentional encoding condition (Intentional condition), participants were asked to try and remember the target items and their list of occurrence and were informed about the format of the subsequent memory test. By contrast, the incidental encoding instructions (Incidental condition) require the encoding of target information in order to perform a memory task without any reference to the contextual information (incidental encoding of context, but intentional encoding of target information). However, according to Mandler, Seegmiller, and Day (1977), this does not prevent the participants from using contextual information (in their study, spatial location information) in order to help them remember the target items. Thus, they suggested that it would be better to use “true” incidental encoding instructions, in which no reference at all is made to a memory test. In the domain of memory for temporal context, Naveh-Benjamin (1990) also encouraged the use of “true” incidental encoding instructions, as standard incidental instructions cannot guarantee that participants do not deliberately use temporal information in order to facilitate the learning of the items. Therefore, in addition to the Intentional and the Incidental encoding conditions, we also included a third condition in our procedure, namely, a “true” incidental encoding condition (True incidental condition), in which the participants performed an orienting task and were not informed about any subsequent memory test. 
	We hypothesized that older adults would not be able to develop strategies in order to encode the temporal context of the items. Following this hypothesis, under incidental encoding conditions, there should be no age differences on list discrimination performance because neither young nor older participants would engage in strategic encoding of temporal context when they did not expect to be tested on temporal information. In contrast, under intentional encoding condition, it is hypothesized that young participants are more likely than older adults to use strategies to help them encode which list the items occurred in. Therefore, we should see a greater age-related decline in this condition. It should also be noted that, if young participants deliberately tried to use temporal information to help them remember the target items in the Incidental condition (Mandler et al., 1977; Naveh-Benjamin, 1990), one would expect relatively similar results in this condition and in the intentional encoding condition.
	As for item recognition, previous studies found that recognition memory for faces was better or equal following judgments about a personality trait than following intentional encoding of faces without any judgment (see Coin & Tiberghien, 1997, for a review). Thus, one could expect equivalent or better face recognition performance in the true incidental encoding condition than in the other two conditions.
Method
Participants 
Forty-eight young subjects and 48 older adults were volunteers in this experiment. The young group, aged from 18 to 26 years old (mean age = 21.81, SD = 2.51), comprised 25 males and 23 females. Most of them were undergraduate students from the University of Liège, Belgium. There were 26 males and 22 females in the older group. Their age ranged from 60 to 70 years old, with a mean of 64.08 (SD = 2.94). The older participants were mainly recruited in rambler's clubs, Church organizations and sports centers for the elderly. All participants reported to be free of neurological or psychiatric disorders and medication interfering with cognitive functioning. The participants were randomly attributed to three different conditions according to the encoding instructions they received. There were 16 young and 16 older participants in each condition. Young and old participants were age-matched across conditions (young group: F(2, 45) = 2.69, p > .08, older group: F(2, 45) = 0.21, p > .81). Both groups were matched on the number of years of education they had received (young group: 14.31  1.73; older group: 14.12  1.70, F(1, 90) = 0.29, p > .59). There was no difference in education between the three conditions, F(2, 90) = 1.56, p > .21, and no interaction between age group and encoding condition, F(2, 90) = 0.33, p > .72.
Materials and Procedure 
The participants were tested individually. The stimuli consisted of 40 black and white photographs of faces. They represented men aged between 20 and 50 years old. No face had any distinctive feature such as a beard, a moustache, glasses, a scar, baldness or long hair. Twenty faces were designated as targets and the others as lures. 
During the study phase, two lists of 10 faces were presented via a personal computer. Each face appeared for 6 s. After the presentation of the first list, participants performed a visual distracting task. In this task that lasted 3 min, they had to select three specific designs among several others. Following this filler task, the second list was presented. There were three different encoding conditions. A different group of participants were tested for each condition. In a first condition (True incidental), the encoding of both faces and lists (temporal context) was incidental. Participants were asked to say for each face whether they found the man likeable or not. In a second condition (Incidental), faces were encoded intentionally, but the encoding of the temporal context was incidental. Participants were instructed to study the faces, but no mention was made of a temporal judgment task. In a third condition (Intentional), participants had to try to remember the faces and the list in which each face appeared and were informed about the subsequent list discrimination task. This study phase was followed by a retention interval of 30 s during which participants had to draw a cross in squares following a route. The test phase then began. Forty faces comprising the 20 targets and 20 lures were presented in a random order fixed for all participants. The faces were presented one at a time and participants had to indicate whether they recognized it or not. When responding “yes”, they were asked to indicate in which list the face appeared (List 1 or 2).
Results
Recognition Accuracy
Recognition performance, expressed by hits and false alarms, was calculated for each age group in each condition (see mean scores and standard deviations in Table 1). A 2  3 analysis of variance (ANOVA), with Age Group (young vs. older group) and Encoding Condition (True incidental, Incidental, and Intentional) as between-subject variables, was conducted on each score. For the hit rates, there was no age difference, F(1, 90) = 1.43, p > .23, no effect of Encoding Condition, F(2, 90) = 2.36, p > .09, and no interaction, F(2, 90) = 0.31, p > .73. 
Older participants made more false alarms than younger participants, F(1, 90) = 47.86, p < .01. There was no effect of Encoding Condition, F(2, 90) = 2.56, p > .08, and no Age Group  Encoding Condition interaction, F(2, 90) = 1.55, p > .22. 
(Table 1 around here)
In order to measure global recognition performance, d’ scores were computed for each participant from the hit and false alarm rates (Macmillan & Creelman, 1991). An ANOVA, with Age Group and Encoding Condition as between-subject variables, revealed a main effect of Age Group, F(1, 90) = 33.60, p < .01, showing that older adults (M = 1.68) had worse recognition performance than younger adults (M = 2.49). There was no main effect of Encoding Condition, F(2, 90) = 0.26, p > .77, and no interaction, F(2, 90) = 0.97, p > .38. Response bias was also analyzed, by means of the criterion c (Macmillan & Creelman, 1991). There was an Age Group effect, F(1, 90) = 16.98, p < .01. Young adults used more severe response criteria than older participants (young: M = .16; older: M = -.13). Neither the effect of Encoding Condition, F(2, 90) = 2.52, p > .08, nor the interaction,  F(2, 90) = 0.03, p > .97, were significant.
List Discrimination Performance
 List discrimination performance can be calculated by means of two measures. The first is the proportion of correctly recognized items that are attributed to the proper list. The second is a z score that takes into account the probability of obtaining a given score by chance1 (Hunkin, Parkin, & Longmore, 1994). Analyses were performed on both measures and yielded similar results. Therefore, we report here only the analysis on z scores. Nonetheless, discrimination performance expressed as proportion of correct discrimination is reported in Table 1.
	List discrimination performance was submitted to an ANOVA with Age Group (young vs. older group) and Encoding Condition (True incidental, Incidental, and Intentional) as between-subject variables. This ANOVA showed a main effect of Age Group, F(1, 90) = 18.98, p < .01. Young participants (M = 1.68) were better at remembering the list of appearance of the faces than were the older participants (M = 0.74). There were no main effect of Encoding Condition, F(2, 90) = 1.79, p > .17, and no interaction, F(2, 90) = 0.34, p > .71.
	Because the decrease of list discrimination performance in older adults occurred in the context of poorer item memory, it is not clear whether there were disproportionate age-related differences on memory for the temporal context. In order to address this issue, we compared subgroups constituted of 29 young and 29 older adults matched on item memory performance (mean d’ scores, young = 2.20, older = 2.04, F(1, 52) = 0.79, p > .37). These two subgroups differed in terms of list discrimination performance measured by z scores (F(1, 52) = 4.06, p < .05), with older adults remembering the temporal context less well than the younger adults (young, M = 1.45, older, M = 0.87). There were no effect of the Encoding Condition, F(2, 52) = 1.44, p > .24, and no interaction, F(2, 52) = 1.57, p > .21. When performance was measured by the proportion of correct discriminations, older adults tended to show a poorer performance than young adults, but the difference did not reach statistical significance, F(1, 52) = 3.82, p < .06.
		Discussion
	The first experiment examined whether encoding instructions influenced the performance of young and older adults on a list discrimination task. The results showed that recognition accuracy decreased with aging. More specifically, older participants made more false alarms, although they correctly recognized as many target faces as younger participants, which is consistent with other studies using unfamiliar faces as material (Bartlett & Leslie, 1986; Bartlett & Fulton, 1991). There was also an effect of age on list discrimination performance, which persisted when young and older adults were matched on item memory performance. Older participants had more difficulty than younger adults to retrieve in which list a face occurred. This age difference was present independently of the encoding instructions. Additionally, intentional encoding instructions did not improve performance compared to incidental encoding conditions either in young adults or in older adults.
	The fact that list discrimination performance was not better following intentional encoding compared to incidental encoding in young adults suggests that temporal information is encoded automatically (Hasher & Zacks, 1979). Several studies reported no improvement from incidental to intentional encoding condition (Auday, Sullivan, & Cross, 1988; Azari, Auday, & Cross, 1989; McCormack, 1984; Toglia & Kimble, 1976). It should be noted that, in these studies, the incidental encoding instructions did not mention the temporal judgment task, but asked to study the stimulus. When comparing “true” incidental encoding and intentional encoding, Naveh-Benjamin (1990) found a significant increase when subjects knew about the subsequent test (in the event, serial order reconstruction). In the present study, there was no difference under any condition. The discrepancy between Naveh-Benjamin’s findings and the present results could be due to methodological differences. Whereas Naveh-Benjamin (1990) provided the same orienting task in the “true” incidental and the intentional encoding conditions, in the current study, the orienting task was used only for the “true” incidental encoding condition. Therefore, the absence of an effect of intentionality could have been due to the difference between the conditions in terms of the presence of the orienting task. However, Mangels (1997) found an effect of intentionality on serial order reconstruction when comparing true incidental encoding and intentional encoding conditions, despite the fact that she provided an orienting task only in the true incidental condition. Alternatively, the type of task used to assess memory for time might determine the effect of intentionality. It could be that serial order reconstruction (Mangels, 1997; Naveh-Benjamin, 1990) benefits more from intentional encoding than list discrimination.
	Face recognition performance was not influenced by encoding instructions in either group. This is consistent with previous findings showing that judgments about a personality trait and intentional learning of the faces without any judgment lead to similar levels of recognition performance (e.g. Biber, Butters, Rosen, Gerstman, & Mattis, 1981; Deffenbacher, Leu, & Brown, 1981; Sporer, 1991).
In the line of Hasher and Zacks' (1979) framework, the finding that intentional encoding of temporal context did not improve list discrimination performance suggests that some temporal information is automatically associated to the events when they enter memory. This account has been referred to as time-tagging theory (Bowers, Verfaellie, Valenstein & Heilman, 1988; Hasher & Zacks, 1979; Yntema & Trask, 1963). In this context, the present results indicate that older adults failed to automatically attach this specific temporal marker to the target information at encoding. However, time-tagging theories are not completely satisfactory, as suggested by Friedman (1993). First, some criteria proposed by Hasher and Zacks (1979) to determine that the encoding of temporal context is automatic have not been met. For example, one of these criteria is that performance should not be affected by practice. Nonetheless, practice seems to improve performance on list discrimination and recency judgments (Underwood & Malmi, 1978; Zacks, Hasher, Alba, Sanft, & Rose, 1984). Second, from a theoretical point of view, the exact nature of the time marker is unclear. It is unlikely that this consists of a label expressed in terms of conventional time, such as the year, month, date and hour, or some indication regarding a kind of internal clock. Alternatively, it might be that some general information representing the list is automatically associated with each item. However, such a list tag would act more like a contextual index than like a timing attribute. Retrieving when an item occurred would then depend on retrieving the information attached to it and remembering which list was characterized by this information.
	An alternative theoretical account is that no specific time marker is encoded together with the event, but that the time of occurrence is reconstructed at retrieval. Friedman (1993, 2001) proposed that at least two processes would be available to retrieve the temporal context of an event. First, the time elapsed since the event occurred may be assessed by the strength, the accessibility or the elaborateness of the memory trace (Hinrichs, 1970). For example, if the memory of an event is vivid, we judge it as recent compared to a weaker memory. According to Friedman (1993, 2001), these distance-based processes require little effort, are rapid, but do not allow precise dating. A second type of process depends on the contextual information encoded at the same time as the event. By interpreting this information in reference to our knowledge about temporal patterns, we can infer as precisely as possible when the event occurred (Friedman & Wilking, 1985; Hintzman, Block & Summers, 1973). For example, one might remember that some excursion occurred when we were in first year at university, because we remember the presence of a teacher who was the tutor of that year. Note that the notion of a time-tagging in which the tag comprises contextual information encoded with the event is similar to these contextual reconstructive processes (Friedman, 1993). These location-based processes2 are slow, strategic and allow more precise dating. As laboratory experiments require precise time estimations, location-based processes may be favored by participants (Friedman, 1993).
In this prospect, the difficulty of older adults may be mainly one of retrieval. Aging may affect either location-based processes or distance-based processes or both. Because location-based processes are effortful and require strategic retrieval of information from memory as well as inferences, it is plausible to hypothesize that aging primarily interferes with these contextual reconstruction processes. Older adults may fail to retrieve the list of occurrence of the faces by relating contextual information encoded in the same time as the face to the temporal structure of the experiment. We do not rule out the possibility that aging also affects distance-based processes. However, the exact nature of these processes is still unclear, and it is difficult to identify components that could be sensitive to aging. 
The absence of an effect of encoding instructions is consistent with the idea that the temporal context is reconstructed at retrieval. Indeed, according to this account, intentional encoding does not necessarily improve performance compared to incidental learning because deliberate attempts to code the time of occurrence add little to the contextual information that is naturally acquired when we process an item. 
Finally, because recognition accuracy was poorer in older adults, it may be that older adults only encode the items superficially and then lack information to reconstruct the time of occurrence of the items. Nonetheless, the finding that age differences on list discrimination remained significant when subgroups matched on item recognition accuracy were examined speaks in favor of a difficulty at the retrieval stage. However, even if older adults fail to use reconstruction processes to retrieve the temporal context of events, one cannot exclude that age differences on list discrimination could be explained at least partly by an encoding difficulty. 
In the second experiment, we explored whether older adults can use location-based processes as well as young adults in order to perform a list discrimination task. 
EXPERIMENT 2
In this experiment, we attempted to see whether older adults were able to use a reconstructive strategy when they were encouraged to rely on it. We associated a different context to each list by manipulating the encoding instructions. The aim of this manipulation was to provide different contextual information for each list, so that this information could be used to retrieve in which list a given face was presented. 
For one list of faces, participants had to say whether the man on the photograph looked intelligent or not. For the other list, they had to say whether each man looked honest or not. Judgments on personality traits produce higher recognition memory than judgments about facial features (e.g. Bower & Karlin, 1974; Parkin & Hayward, 1983, see Coin & Tiberghien, 1997 for a review). Judgments on honesty and intelligence should result in relatively equivalent memory performance. 
Young and older adults performed this task and half of them were encouraged to remember the condition under which they encoded the face as a cue to retrieve its list of occurrence. The other half did not receive any particular instructions regarding how to retrieve the list of occurrence. Additionally, we assessed how well the participants remembered the encoding context and we related this to the list discrimination performance. We predicted that greater age differences should be observed when participants used the proposed reconstructive strategy, because this condition places increased demands on cognitive resources which may be reduced in older participants (Light, 1991).
Method
Participants
 Forty young subjects (21 men and 19 women) and 39 older adults (20 men and 19 women) took part to this experiment. The young group consisted mainly of undergraduate students from the University of Liège, Belgium. The mean age was 20.82 years old (SD = 2.11) (range from 18 to 28). The mean age of the older group was 63.77 years old (SD = 3.26) (range from 60 to 70). All participants reported to be free of neurological or psychiatric disorders and medication interfering with cognitive functioning. Both groups were matched on the number of years of education they had received (young group: 13.35  1.31; older group: 13  1.43, t(77) = 1.13, p > .26). On a vocabulary test (Mill Hill, part B, 33 items; Deltour, 1993), older adults performed better than young adults, young group: 22.92  3.73; old group: 25.10  5.37, t(75) = -2.06, p < .05. 
Materials and Procedure
The stimuli and the procedure were identical to those in Experiment 1, except with the encoding and retrieval instructions. During the study phase, each list of 10 faces was encoded under a different condition. For one of the list, participants were instructed to rate how intelligent the person on the photograph looked. For their judgments, they used a 5-point scale, from 1 (very intelligent) to 5 (not intelligent at all). For the other list, participant had to rate how honest the person looked (from 1 very honest to 5 not honest at all). The attribution of each type of judgment to each list was counterbalanced across participants.
During the test phase, there were two retrieval instructions. Half of the participants in each group were asked to say whether they recognized the faces or not, and to say in which list the face appeared (List 1 or 2) every time they recognized it (“No strategy”). The other half of the participants were additionally encouraged to remember the type of judgment they made at encoding to retrieve the list of occurrence of the faces (“Strategy”).
After the task, we asked to the participants how they discriminated between list 1 and 2. Additionally, when participants in the group with the reconstruction strategy reported that they used the proposed strategy, they were asked how often they had used it (on a 3-point scale: 1 for a few faces, 2 for most faces, and 3 for all the faces) and whether they had found it useful (on a 5-point scale from 1 not useful at all to 5 very useful).
Finally, memory for the type of judgment made at encoding was assessed. The 20 target faces were presented in a random order. Participants were informed that they had seen all the faces and that the task consisted in saying for each face whether they made an “honesty” or an “intelligence” judgment when they saw it during the study phase. The purpose of that task was to check whether the contextual information associated to each list was available for young and older adults to use as a cue in the list discrimination task.
Results
Retrieval Strategy Manipulation
	Responses to the post-task questionnaire revealed that, in the condition where the reconstruction strategy was proposed, 18 young participants out of 20 and 16 older participants out of 20 used it. In the “No Strategy” condition, 7 young participants out of 20 and 8 older participants out of 19 tried to remember the type of judgment made at encoding to retrieve the list, although no mention to this strategy was made, while 13 young participants and 11 older participants tried to retrieve the list by means of other processes than the reconstruction of the encoding context of the list. Comments revealed that they usually referred to the strength of the memory for the item to situate it in time (e.g. “I tried to see whether it seemed far in time or not”, “I judged how recent it was”, “I do not remember the first list very well”).
	Among participants who used the reconstruction strategy, young adults did not report using it for more faces than older participants, F(1, 37) = 0.59, p > .44 (young, M = 2.1 and old, M = 1.89 on the 3-point scale). Moreover, young and older participants found the strategy equally useful, F(1, 37) = 2.37, p > .13 (young, M = 3.05 and old, M = 2.53 on the 5-point scale).
Recognition Accuracy. The top rows of Table 2 present recognition performance, expressed by hits and false alarms rates, for each age group in each condition. A 2  2 ANOVA, with Age Group (young vs. older group) and Retrieval Instructions (“No Strategy” vs. “Strategy”) as between-subject variables, was conducted on each score. For hit rates, there was no age difference, F(1, 75) = 0.01, p > .93, no effect of Retrieval Instructions, F(1, 75) = 1.87, p > .17, and no interaction, F(1, 75) = 0.14, p > .70. Regarding the false alarms, older participants incorrectly recognized more new faces than did the younger participants, F(1, 75) = 6.24, p < .05. There was no effect of Retrieval Instructions, F(1, 75) = 0.01, p > .94, and no Age Group  Retrieval Instructions interaction, F(1, 75) = 1.14, p > .28.
	In order to see whether one type of encoding judgment led to better recognition performance than the other, we conducted an ANOVA on hits with Age Group and Retrieval Instructions as between-subject variables and Type of Judgment (honesty vs. intelligence) as within-subject variable. No effect was significant.
Global recognition performance, as measured by d’ scores, was submitted to an ANOVA with Age Group and Retrieval Instructions as between-subject variables. The analysis showed no main effect of Age Group, F(1, 75) = 2.12, p > .14, (young: M = 1.85; older: M = 1.62), no main effect of Retrieval Instructions, F(1, 75) = 0.97, p > .32, and no interaction, F(1, 75) = 0.69, p > .40. Response bias (c) analysis showed no main effect of Age Group, F(1, 75) = 1.99, p > .16, (young: M = .21; older: M = .07), no effect of Retrieval Instructions, F(1, 75) = 1.56, p > .21, and no interaction, F(1, 75) = 0.04, p > .82.
(Table 2 around here)
List Discrimination Performance. Analysis performed on the two measures of list discrimination performance (proportion of recognized targets correctly attributed to the list and z score) yielded similar results. As in Experiment 1, we report only the analysis on z scores (see Figure 1a) and provide proportions of correct discrimination for each Age group and in each Retrieval Instructions condition in Table 2 (top rows).
	List discrimination performance was submitted to an ANOVA with Age Group (young vs. older group) and Retrieval Instructions (“No Strategy” vs. “Strategy”) as between-subject variables. There was a main effect of Age Group, F(1, 75) = 8.44, p < .01. Young participants performed better on the list discrimination task than older participants. There was no main effect of Retrieval Instructions, F(1, 75) = 1.03, p > .31, and no Age group  Retrieval Instructions interaction, F(1, 75) = 0.07, p > .78. 
	Self-reports in the post-task questionnaire revealed that, in addition to the participants in the Strategy condition who used the proposed reconstruction strategy for the vast majority, 35 % of the young participants and 42 % of the older participants in the No Strategy condition also reported using this strategy. As noted previously, the remaining participants in the No Strategy condition reported some processes that may be described as assessing the strength of the memory for the items. Therefore, it may be that a potential effect of the type of processes used to reconstruct the temporal context was masked in the comparison between the Strategy and No Strategy groups. Consequently, the results were further analyzed in order to examine the effect of the processes actually used by the participants on list discrimination performance
(Figure 1 around here)
Self-Reported Retrieval Processes
	The participants were divided in two groups (independently of their original retrieval condition) according to whether they actually used the reconstruction strategy (“Reconstruction”, young group: n = 25, including 18 participants from the “Strategy” condition and 7 from the “No strategy” condition; older group: n = 24, including 16 participants from the “Strategy” condition and 8 from the “No strategy” condition) or some other processes involving mainly evaluation of the age of the memory (“Distance”, young group: n = 15, comprising 2 participants from the “Strategy” condition and 13 from the “No strategy” one, older group: n = 15, that is 4 participants from the “Strategy” condition and 11 from the “No strategy” condition).
	These two groups did not differ according to the age of the participants (young group, F(1, 38) = 0.4, p > .83, and older group, F(1, 37) = 1.92, p > .17). Education was equivalent between young and older participants, F(1, 75) = 1.53, p > .22, between “Reconstruction” and “Distance” conditions, F(1, 75) = 0.51, p > .47, and there was no Age Group  Retrieval Processes interaction, F(1, 75) = 0.4, p > .53. Finally, older adults performed slightly better on the Mill Hill Vocabulary test, although the effect did not reach significance, F(1, 73) = 3.95, p < .06. There was no effect of the Retrieval Processes, F(1, 73) = 0.32, p > .57 and no interaction, F(1, 73) = 0.01, p > .98.
Recognition Accuracy. Table 2 (bottom rows) presents recognition performance, expressed by hits and false alarms rates, for each age group in each condition. A 2  2 ANOVA, with Age Group (young vs. older group) and Retrieval Processes (“Reconstruction” vs. “Distance”) as between-subject variables, was conducted on each score. For hit rates, there was no age difference, F(1, 75) = 0.01, p > .94, no effect of Retrieval Processes, F(1, 75) = 0.48, p > .49, and no interaction, F(1, 75) = 0.6, p > .44. Analysis of false alarms rates revealed a main effect of Age Group, F(1, 75) = 5.20, p < .05, with a higher rate of false alarms in older participants than in younger participants. There was no effect of Retrieval Processes, F(1, 75) = 3.01, p > .08, and no Age group  Retrieval Processes interaction, F(1, 75) = 0.57, p > .45.
	Global recognition performance was measured by d’ scores. An ANOVA with Age Group and Retrieval Processes as between-subject variables indicated no main effect of Age Group, F(1, 75) = 1.14, p > .29, (young: M = 1.81; older: M = 1.63), no main effect of Retrieval Processes, F(1, 75) = 0.41, p > .52, and no interaction, F(1, 75) = 2.43, p > .12. Response bias (c) analysis showed no main effect of Age Group, F(1, 75) = 1.85, p > .18, (young: M = .19 ; older: M = .05). The effect of Retrieval Processes was not significant, F(1, 75) = 2.85, p > .09, nor was the interaction, F(1, 75) = 0.01, p > .97. 
List Discrimination Performance. List discrimination performance measured by z scores (see Figure 1b) was submitted to an ANOVA with Age Group (young vs. older group) and Retrieval Processes (“Reconstruction” vs. “Distance”) as between-subject variables. Analysis on proportions of correct discriminations gave similar results (see bottom rows of Table 2). There was a main effect of Age Group, F(1, 75) = 6.23, p < .05. Young participants performed better on the list discrimination task than older participants. There was no main effect of Retrieval Processes, F(1, 75) = 2.04, p > .16. The Age group  Retrieval Processes interaction did not reach significance, F(1, 75) = 3.18, p > .07. However, post-hoc comparisons (Newman-Keuls) revealed that the pattern of results was different for each age group. Young participants performed as well in the “Distance” condition as in the “Reconstruction” condition (p > .80). By contrast, older adults remembered better the list of occurrence of the items in the “Distance” condition than in the “Reconstruction” condition (p < .05). Additionally, in the “Distance” condition, there was no effect of Age group (p > .65), whereas young adults’ performance was significantly higher than that of older adults in the “Reconstruction” condition (p < .01).
Memory for the Encoding Context. Proportions of correct responses in the task requiring to recall the type of encoding task were submitted to an ANOVA with Age Group (young vs. older group) and Retrieval Processes (“Reconstruction” vs. “Distance”) as between-subject variables. Young adults performed better than older adults (young: M = .60, SD = .10, old: M = .54, SD = .12, F(1, 71) = 4.27, p < .05). Neither the effect of Retrieval Processes, F(1, 71) = 0.69, p > .41, nor the interaction, F(1, 71) = 0.01, p > .94, were significant. A comparison of the scores of the older group against chance (.50) indicated that they could remember the encoding context at a level above chance (t(35) = -2.41, p < .05).
	In order to assess whether memory for the encoding context influences the list discrimination performance, we computed in which proportion each participant correctly retrieved the list of occurrence of items for which they remembered the encoding context. An ANOVA with Age Group and Retrieval Processes showed that, when they remembered the type of judgment made at encoding, young participants (M = .58) correctly retrieved the list of occurrence more often than did older participants (M = .47), F(1, 71) = 4.99, p < .05. There was no effect of Retrieval Processes, F(1, 71) = 1.19, p > .27, and no interaction, F(1, 71) = 0.47, p > .49. In addition, we calculated how often each participant remembered the encoding context of items that they have been able to attribute to the correct list. An ANOVA with Age Group and Retrieval Processes as between-subject variables indicated a main effect of Age Group, F(1, 71) = 4.38, p < .05, and no effect of Retrieval Processes, F(1, 71) = 1.07, p > .30. The Age Group  Retrieval Processes interaction was not significant, F(1, 71) = 3.16, p > .07, but post-hoc comparisons (Newman-Keuls) showed that in the “Reconstruction” condition, young and older participants remembered the encoding context for an equivalent proportion of recognised items attributed to the correct list (respectively, 67 and 65% of the correct discriminations, p > .82). By contrast, in the “Distance” condition, older participants retrieved less often the encoding context than young participants (young: 70%, old: 52%, p < .05).
Discussion
	Experiment 2 examined whether aging affects the ability to use reconstructive processes to retrieve the temporal context of events. In order to create a different encoding context for each list, two different semantic judgments were made on each set of faces. Half of the participants were encouraged to try to remember the encoding context of the items as a cue for retrieving their list of occurrence and most of them did use the proposed strategy. The other half received standard list discrimination instructions. 
The results indicated that older adults were poorer than younger adults in remembering in which list the faces were presented and that the instructions did not influence performance in either group. However, the self-reports in the post-task questionnaire indicated that around 35-40 % of the participants who did not receive any instruction mentioning the reconstructive strategy spontaneously used their memory for the type of judgment made on the face in the list discrimination task. As for the participants who did not use this process, their comments suggested that most of them might have relied on some distance-based processes (Friedman, 1993).
	When the data were analyzed according to the processes that the participants actually used to discriminate between list 1 and 2, it appeared that older adults had difficulties in remembering the list of occurrence of the faces when they reconstructed it from the encoding context, but not when they used distance-based processes. A tentative conclusion would be that aging may particularly affect location-based processes. However, cautious interpretation is necessary because these findings results from a reallocation of the subjects to new groups according to the retrieval processes they actually used and because the Age group by Retrieval processes interaction did not reach significance. 
It should be noted that older adults performed worse in the “Reconstruction” condition than in the “Distance” condition. Actually, performance was very low in the former condition (M = .55). This cannot be explained by the inefficiency of the strategy itself because young participants performed as well in the “Reconstruction” condition as when they used other processes. A first possibility is that older adults may not remember the contextual information associated with the items, and hence cannot use it as the basis for the location-based processes. In fact, the results for the task assessing memory for the type of judgment made at encoding indicate that older adults did not recall the encoding context as well as young adults did. However, when considering only the items for which the participants could remember the encoding context, older adults still failed to retrieve the list of occurrence, compared to young adults. Therefore, even if a less efficient encoding of the contextual information associated with each list may have contributed to the difficulty in memory for the temporal context in older adults, an additional retrieval difficulty may also play a role. It may be that the reconstruction strategy was too demanding for older participants. Older adults may have had more difficulty than younger adults in engaging in strategic inferences, as this is an effortful process and older adults have a reduction of attentional resources (Light, 1991). 
	The fact that older adults performed as well as younger participants in the “Distance” condition is intriguing. A possible interpretation would be that distance-based processes are preserved in normal aging, as proposed by Friedman and Huttenlocher (1997). These authors examined how well participants can judge when they have seen stories presented in a weekly television show. Because it is likely that most participants watched the show as part of a kind of routine, involving a uniform context, they may rely mainly on some distance-based process to estimate when they saw a story. In Experiment 2 of Friedman and Huttenlocher’s study, participants below and above 60 years old performed in exactly the same way on this task, suggesting that aging does not affect distance-based processes. However, it is important to note that it is most probable that participants used a mixture of both distance-based and location-based processes in order to discriminate the list of occurrence of events. As for the present experiment, we do not argue that only location-based information is used in the Reconstruction condition. Questionnaire’s responses only indicated that participants tried to rely on contextual cues for most of the trials. The same is true for participants who did not report using the reconstructive strategy. Although post-task reports suggested that distance-based processes may have usually been used predominantly, they probably may also have used some location-based processes, based on some contextual information other than that related to the type of judgment made at encoding (for example, to relate items to temporal landmarks such as the beginning or the end of the list). Therefore, we cannot exclude that older participants sometimes relied on location-based processes in the Distance condition. Future work should compare conditions where either a distance-based strategy or a location-based strategy is forced.
GENERAL DISCUSSION
In the present study, we reexamined the effect of aging on memory for the temporal context, measured by a list discrimination task. As in previous studies (Spencer & Raz, 1995), we found a decline of memory for temporal context in older adults, whereas memory for the item seemed less affected (particularly in Experiment 2). It is intriguing that age differences appeared on item recognition accuracy in Experiment 1, but not in Experiment 2. This cannot be due to differences in age between the participants in each experiment. Indeed, there were no differences in terms of age between the young groups across the two experiments, nor between the two older groups (young group: F(1, 171) = 2.85, p > .09; old group: F(1, 171) = 0.28, p > .59). By contrast, the participants in Experiment 1 reported less years of education than the participants in Experiment 2 (F(1, 171) = 19.19, p < .01). Therefore, it could be that the probability of age differences on item memory decreases as the amount of education received increases. Alternatively, the divergence in item recognition between the experiments could be a consequence of the task instructions. Indeed, it has been shown that age differences can be substantially reduced when the encoding instructions do not emphasize the fact that memory capacity will be evaluated (Rahhal, Hasher, & Colcombe, 2001). This could explain why deciding if a face is honest or intelligent leads to a smaller age effect in item memory than preparing for a memory test. But, if this is true, one would also expect a reduction of age differences on item memory in the true incidental encoding condition in Experiment 1.
We explored whether aging particularly affects the encoding of temporal information, or its retrieval, or both. In Experiment 1, intention to encode the temporal context was manipulated in order to see whether participants would develop some organizational strategies when informed that they have to remember the list of occurrence of items, and whether aging would affect the ability to use these strategies. The results indicated that intentional encoding did not improve list discrimination performance compared to incidental encoding. Furthermore, older participants had a poorer performance independently of the encoding condition. One explanation could be that temporal information is automatically associated to the target information at encoding and that aging affects this temporal coding. An alternative interpretation, which we favor, refers to the idea that temporal context is not an attribute of an event, but rather is reconstructed on the basis of some quality of the event itself: the strength of its memory trace (distance-based processes) or the contextual information naturally encoded with the event (location-based processes, Friedman, 1993, 2001). From this point of view, the effect of age on memory for time could result from a difficulty with one of these retrieval processes or both. A difficulty to use location-based processes would affect the reconstruction of the temporal information on the basis of information characterizing the list and associated with each face, independently of the encoding condition. This difficulty may arise from a failure to automatically attach this information to the item at encoding or because of decreased inference abilities at retrieval. A difficulty to use distance-based processes would prevent older adults from assessing how recent is the encounter with each item.
In Experiment 2, we tested the hypothesis that aging may interfere with the ability to infer the time of occurrence of an event from the contextual information encoded in the same time as the event and by reference to some temporal patterns. Different contextual information was associated with each list and half of the participants were encouraged to rely on this information to infer in which list an item occurred. We compared the performance of the participants who followed this instruction or used this strategy spontaneously with that of the participants who relied on some other processes, usually involving some assessment of the temporal distance. Age differences were found only when participants tried to retrieve the temporal context of the items by remembering its encoding context. Although these results must be considered as preliminary because they were found after regrouping the subjects, they raise the interesting possibility that aging decreases the ability to use location-based processes. Furthermore, as memory for the encoding context itself was poorer in older participants, this difficulty could stem in part from a poorer encoding of the contextual details of the events. However, the fact that list discrimination performance was poor in older adults even when they remembered correctly the encoding context suggests that aging interferes with the use of strategic inferences for reconstructing the temporal context. Distance-based processes could be less affected by aging as suggested by Friedman and Huttenlocher (1997). However, the results in the Distance condition must be interpreted with caution because the identification of the processes was based on post-task reports. In addition, further clarification of what these processes are is necessary in order to understand how they evolve with aging.
If indeed location-based processes are more vulnerable to aging than distance-based processes, could the age effect on list discrimination performance found in Experiment 1 be attributed to defective location-based processes? This is possible according to Friedman’s (1993) statement that location-based processes should be selected over distance-based processes in most laboratory experiments, because the former allow greater accuracy and confidence. Alternatively, as a proportion of participants in the “No strategy” condition of Experiment 2 reported that they used mainly distance-based processes, it might be that at least some of the participants in Experiment 1 also favored these processes. If this was the case, one cannot exclude that aging also affects distance-based processes. However, the question cannot be unequivocally resolved as there was no information available regarding which type of processes the participants favored in Experiment 1. 
It should be noted that Fabiani and Friedman’s (1997) findings seem consistent with the current interpretation. They found age-related decrements in recency judgments, particularly when the material consisted of pictures, compared to words. They proposed that comparing the strength of the traces of two pictures might be less efficient to identify which one occurred later in the list than comparing the strength of the traces of two words. Because words seem to be more quickly forgotten than pictures, the difference in the trace strengths should be more important for words than for pictures. Moreover, some recency judgments trials for words may become similar to a recognition test when the trace of one of the items is lost. By contrast, the strength of the traces of two pictures may be more similar and thus, this makes distance-based processes less reliable. In such cases, location-based processes may be more useful to discriminate which one occurred last, although it is difficult to say whether young participants in Fabiani and Friedman’s study were able to use these processes. Older participants’ poorer performance in the recency judgments for pictures could have resulted from a reliance on inefficient distance-based processes and a difficulty to compensate with other processes. 
In summary, the results from this study tentatively suggest that the effect of age on memory for the temporal context may arise from a difficulty in initiating the strategic reconstruction of the temporal information at the retrieval stage. Moreover, a less efficient encoding of the contextual details associated with the items could also contribute to this difficulty. By contrast, it might be that aging less disrupts distance-based processes. Future research should explore the effect of aging on tasks that dissociate location-based and distance-based processes.

References

Auday, B. C., Sullivan, C., & Cross, H. A. (1988). The effects of constrained rehearsal on judgments of temporal order. Bulletin of the Psychonomic Society, 26, 548-551.
Azari, N. P., Auday, B. C., & Cross, H. A. (1989). Effect of instructions on memory for temporal order. Bulletin of the Psychonomic Society, 27, 203-205.
Bartlett, J. C. & Fulton, A. (1991). Familiarity and recognition of faces in old age. Memory and Cognition, 19, 229-238.
Bartlett, J. C. & Leslie, J. E. (1986). Aging and memory for faces versus single views of faces. Memory and Cognition, 14, 371-381.
Biber, C., Butters, N., Rosen, J., Gerstman, L., & Mattis, S. (1981). Encoding strategies and recognition of faces by alcoholic Korsakoff and other brain-damaged patients. Journal of Clinical Neuropsychology, 3, 315-330.
Bower, G. H., & Karlin, M. B. (1974). Depth of processing pictures of faces and recognition memory. Journal of Experimental Psychology, 103(4), 751-757.
Bowers, D., Verfaellie, M., Valenstein, E., & Heilman, K. M. (1988). Impaired acquisition of temporal information in retrosplenial amnesia. Brain and Cognition, 8, 47-66.
Coin, C. & Tiberghien, G. (1997). Encoding activity and face recognition. Memory, 5, 545-568.
Craik, F. I. M. & McDowd, J. M. (1987). Age differences in recall and recognition. Journal of Experimental Psychology : Learning, Memory and Cognition, 13, 474-479.
Daum, I., Gräber, S., Schugens, M. M., & Mayes, A. R. (1996). Memory dysfunction of the frontal type in normal ageing. NeuroReport, 7, 2625-2628.
Deffenbacher, K. A., Leu, J. R., & Brown, E. L. (1981). Memory for faces: Testing method, encoding strategy, and confidence. American Journal of Psychology, 94, 13-26.
Deltour, J.-J. (1993). Echelle de vocabulaire de Mill Hill de J.C. Raven. Adaptation française et normes comparées du Mill Hill et du Standard Progressive Matrices (PM 38). Manuel. Braine-le-Château: Editions L’Application des Techniques Modernes.
Fabiani, M. & Friedman, D. (1997). Dissociations between memory for temporal order and recognition memory in aging. Neuropsychologia, 35, 129-141.
Friedman, W. J. (1993). Memory for the time of past events. Psychological Bulletin, 113, 44-66.
Friedman, W. J. (2001). Memory processes underlying humans' chronological sense of the past. In C.Hoerl & T. McCormack (Eds.), Time and memory : Issues in philosophy and psychology (pp. 139-167). Oxford: Clarendon Press.
Friedman, W. J. & Huttenlocher, J. (1997). Memory for the time of "60 Minutes" stories and news events. Journal of Experimental Psychology : Learning, Memory and Cognition, 23, 560-569.
Friedman, W. J. & Wilkins, A. J. (1985). Scale effects in memory for the time of events. Memory and Cognition, 13, 168-175.
Glisky, E. L., Polster, M. R., & Routhieaux, B. C. (1995). Double dissociation between item and source memory. Neuropsychology, 9, 229-235.
Glisky, E. L., Rubin, S. R., & Davidson, P. S. R. (2001). Source memory on older adults : An encoding or retrieval problem ? Journal of Experimental Psychology : Learning, Memory and Cognition, 27, 1131-1146.
Hasher, L. & Zacks, R. T. (1979). Automatic and effortful processes in memory. Journal of Experimental Psychology : General, 108, 356-388.
Hinrichs, J. V. (1970). A two-process memory-strength theory for judgment of recency. Psychological Review, 77, 223-233.
Hintzman, D. L., Block, R. A., & Summers, J. J. (1973). Contextual associatios and memory for serial position. Journal of Experimental Psychology, 97(2), 220-229.
Hunkin, N. M., Parkin, A. J., & Longmore, B. E. (1994). Aetiological variation in the amnesic syndrome : Comparisons using the list discrimination task. Neuropsychologia, 32, 819-825.
Johnson, M. K., Hashtroudi, S., & Lindsay, D. S. (1993). Source monitoring. Psychological Bulletin, 114, 3-28.
Kausler, D. H., Salthouse, T. A., & Saults, J. S. (1988). Temporal memory over the adult lifespan. American Journal of Psychology, 101, 207-215.
La Voie, D. & Light, L. L. (1994). Adult age differences in repetition priming : a meta-analysis. Psychology and Aging, 9, 539-553.
Light, L. L. (1991). Memory and aging: Four hypotheses in search of data. Annual Review of Psychology, 42, 333-376.
Macmillan, N. A. & Creelman, C. D. (1991). Detection theory : A user's guide. Cambridge: Cambridge University Press.
Mandler, J. M., Seegmiller, D., & Day, J. (1977). On the coding of spatial information. Memory and Cognition, 5, 10-16.
Mangels, J. A. (1997). Strategic processing and memory for temporal order in patients with frontal lobe lesions. Neuropsychology, 11, 207-221.
McCormack, P. D. (1982). Temporal coding and study-phase retrieval in young and elderly adults. Bulletin of the Psychonomic Society, 20, 242-244.
McCormack, P. D. (1984). Temporal coding by young and elderly adults in a list-discrimination setting. Bulletin of the Psychonomic Society, 22, 401-402.
Naveh-Benjamin, M. (1990). Coding of temporal order information : An automatic process ? Journal of Experimental Psychology : Learning, Memory and Cognition, 16, 117-126.
Newman, M. C., Allen, J. J. B., & Kaszniak, A. W. (2001). Tasks for assessing memory for temporal order versus memory for items in aging. Aging, Neuropsychology, and Cognition, 8, 72-78.
Nyberg, L., Maitland, S. B., Rönnlund, M., Bäckman, L., Dixon, R. A., Wahlin, A., & Nilsson, L.-G. (2003). Selective adult age differences in an age-invariant multifactor model of declarative memory. Psychology and Aging, 18, 149-160.
Parkin, A. J. & Hayward, C. (1983). The influence of trait and physical-feature-based orienting strategies on aspects of facial memory. British Journal of Psychology, 74, 71-82.
Parkin, A. J., Walter, B. M., & Hunkin, N. M. (1995). Relationships between normal aging, frontal lobe function, and memory for temporal and spatial information. Neuropsychology, 9, 304-312.
Perfect, T. & Dasgupta, Z. R. R. (1997). What underlies the deficit in reported recollective experience in old age ? Memory and Cognition, 25, 849-858.
Perlmutter, M., Metzger, R., Nezworski, T., & Miller, K. (1981). Spatial and temporal memory in 20 and 60 years olds. Journal of Gerontology, 36, 59-65.
Rahhal, T. A., Hasher, L., & Colcombe, S. J. (2001). Instructional manipulations and age differences in memory: Now you see them, now you don't. Psychology and Aging, 16, 697-706.
Salthouse, T. A. (1992). Mechanisms of age-cognition relations in adulthood. Hillsdale, NJ: Erlbaum.
Spencer, W. D. & Raz, N. (1994). Memory for facts, source, and context : Can frontal lobe dysfunction explain age-related differences? Psychology and Aging, 9, 149-159.
Spencer, W. D. & Raz, N. (1995). Differential effects of aging on memory for content and context : A meta-analysis. Psychology and Aging, 10, 527-539.
Sporer, S. L. (1991). Deep-deeper-deepest? Encoding strategies and the recognition of human faces. Journal of Experimental Psychology : Learning, Memory and Cognition, 17, 323-333.
Toglia, M. P. & Kimble, G. A. (1976). Recall and use of serial position information. Journal of Experimental Psychology : Human Learning and Memory, 2, 431-445.
Tulving, E. (1995). Organization of memory : quo vadis ? In M.S.Gazzaniga (Ed.), The cognitive neurosciences (pp. 839-847). Cambridge: A Bradford Book, The MIT Press.
Tzeng, O. J. L. & Cotton, B. (1980). A study-phase retrieval model of temporal coding. Journal of Experimental Psychology : Human Learning and Memory, 6, 705-716.
Underwood, B. J. & Malmi, R. A. (1978). Transfer from recency learning to corresponding two-category classification learning. Bulletin of the Psychonomic Society, 11, 200-202.
Vakil, E. & Tweedy, J. R. (1994). Memory for temporal order and spatial position information : Tests of the automatic-effortful distinction. Neuropsychiatry, 7, 281-288.
Wegesin, D. J., Jacobs, D. M., Zubin, N. R., Ventura, P. R., & Stern, Y. (2000). Source memory and encoding strategy in normal aging. Journal of Clinical and Experimental Neuropsychology, 22, 455-464.
Whiting, W. L. & Smith, A. D. (1997). Differential age-related processing limitations in recall and recognition tasks. Psychology and Aging, 12, 216-224.
Yntema, D. B. & Trask, F. P. (1963). Recall as a search process. Journal of Verbal Learning and Verbal Behavior, 2, 65-74.
Zacks, R. T., Hasher, L., Alba, J. W., Sanft, H., & Rose, K. C. (1984). Is temporal order encoded automatically ? Memory and Cognition, 12, 387-394.

Author's Note

Christine Bastin, Department of Cognitive Sciences, University of Liège; Martial Van der Linden, Cognitive Psychopathology Unit, University of Geneva, and Department of Cognitive Sciences, University of Liège.
This work was supported by a grant from the French Community of Belgium: “Actions de Recherche Concertées (convention 99/04-246)”.
Correspondence concerning this article should be addressed to Christine Bastin, Department of Cognitive Sciences, University of Liège, Boulevard du Rectorat, B33, B-4000 Liège (Sart-Tilman), Belgium. E-Mail: Christine.Bastin@ulg.ac.be.

Footnotes

1. Z-score formula : z = (r – x)/SD, where r = number discriminated correctly, n = number recognized, p = probability of discriminating a recognized item correctly by chance, x = n.p, SD = square root of (n.p.q), and q = (1-p).
2. The term “location” refers to the fact that the events belong to a particular period of time. Each event can be located in one part of natural, personal or conventional time patterns, such as the cold season, when we were at the university or the weekend (Friedman, 1993, 2001).

Table 1
Mean Proportions (and Standard Deviations) of Hits, False Alarms and Correct Discrimination as a Function of Age Group and Encoding Condition in Experiment 1.

		Hits		False alarms		List discrimination	
Condition		Young	Older		Young	Older		Young	Older	
True incid.		.83 (.11)	.81 (.12)		.08 (.05)	.22 (.10)		.71 (.16)	.56 (.11)	
Incidental		.79 (.12)	.78 (.14)		.10 (.11)	.23 (.11)		.67 (.10)	.58 (.14)	
Intentional		.88 (.09)	.82 (.10)		.10 (.10)	.33 (.19)		.73 (.14)	.63 (.11)	
Note. True incid. = true incidental encoding; Incidental = incidental encoding of context.

Table 2
Mean Proportions (and Standard Deviations) of Hits, False Alarms and Correct Discrimination as a Function of Age Group, Retrieval Instructions (Top Rows) and Retrieval Processes (Bottom Rows) in Experiment 2.

		Hits		False alarms		List discrimination	
Condition		Young	Older		Young	Older		Young	Older	
No Strategy		.76 (.16)	.77 (.17)		.17 (.10)	.21 (.10)		.68 (.14)	.60 (.15)	
Strategy		.72 (.17)	.70 (.17)		.14 (.10)	.24 (.20)		.67 (.16)	.56 (.15)	
										
Distance		.74 (.15)	.77 (.18)		.20 (.11)	.25 (.13)		.66 (.16)	.64 (.13)	
Reconstruction		.74 (.17)	.71 (.16)		.12 (.09)	.22 (.17)		.68 (.14)	.55 (.15)	

Figure caption

Figure 1. List discrimination performance (z score) as a function of age group, retrieval instructions (1a) and retrieval processes (1b) in Experiment 2. Error bars represent standard deviations.

Figure 1

(a)

(b)