Changes in a metacognitive heuristic in amnesia

Amnesic patients rely predominantly on familiarity for recognition. This familiarity is thought to be based on processing fluency. However whether amnesic patients use normally this metacognitive heuristic is not yet known. We used the Jacoby and Whitehouse (1989)’s illusion paradigm with 8 patients with severe memory impairments and 16 matched control. We found a fluency effect, with more “old” responses being given to matched-prime test words than to mismatched-prime test words. In addition, we replicated the effect of modality (Westerman et al., 2002) in the control group. The fluency induced the recognition illusion, but only when there was a match between study and test sensory modality. However, this modality effect seems limited to control participants. Amnesic patients seem unable to disregard fluency when there was a shift in the sensory modality of the study and test stages. Overall, these findings support the notion that amnesic patients did not modulate their use of the fluency heuristic in situations where fluency is judged non-diagnostic of prior exposure by healthy participants.

On the whole, these findings suggest that processing fluency can constitute a cue for recognition decision in amnesia. However, this influence is not direct and is subject to metamemorial belief changes.