Long-term memory effects in working memory are not always automatic: evidence from the imageability effect

Verbal working memory (WM) is influenced by linguistic knowledge; this influence is considered to reflect non-strategic linguistic activation during WM. This may however not be true for the influence of semantic knowledge as involved in the imageability effect (recall of high vs. low imageability words). We assessed the role of controlled processes such as semantic elaboration in the occurrence of the imageability effect. Sixty participants recalled six-item lists composed of high or low imageability words, with an interfering task presented during encoding for half of trials. The interfering task either involved semantic judgment supposed to prevent semantic elaboration processes, or similarly demanding visuo-spatial judgement processes. We observed robust evidence for a reduced word imageability effect in the semantic but not in the visuo-spatial interfering condition. These results suggest that the occurrence of the imageability effect in WM tasks relies partially on semantic elaboration strategies.