Familiarity influences on proactive interference in verbal memory

Proactive interference occurs when older memories interfere with current information processing and retrieval. It is often explained with reference to familiarity, where the reappearance of highly familiar items from the recent past produces more disruption than older, less familiar items. However, there are other forms of familiarity beyond recency that may be important, and these were explored in a verbal recent-probes task. Participants viewed eight targets per trial and then determined whether a probe matched any of those targets. Probes matching a target from the previous trial, rather than an earlier trial, led to more errors, revealing proactive interference. However, this effect was influenced by experimental familiarity (whether stimuli were repeated or unique) and pre-experimental familiarity (whether stimuli were meaningful words or meaningless non-words). Specifically, proactive interference was strongest for repeated non-words, and smallest for unique non-words, but stimulus repetition had little impact for words. In addition, the time separating trials (temporal familiarity) was unrelated to proactive interference. The present findings revealed more complex effects of familiarity than have previously been assumed. To understand proactive interference in a working memory task, it is necessary to consider the role of long-term memory via experimental and pre-experimental stimulus familiarity.