A negative semantic similarity effect on short-term order memory: evidence from recency judgements

Speeded recency judgements were used to examine whether judgements concerning the relative temporal order in which two items were presented on a short eight-item, study list would be facilitated or hindered when the two items were from the same semantic category (related, R, items), relative to when they were from different categories (unrelated, U, items). Semantic similarity led to slower and less accurate recency judgements. To evaluate the extent that item memory contributes to recency judgement performance, I used speeded pair recognition and speeded two-alternative forced-choice (2AFC) recognition trials, in which the stimuli and designs were the same as in the recency judgement test. The type of test trial was manipulated between subjects (recency judgement vs pair recognition) or within participants (recency judgement and 2AFC recognition). Regardless of the between- or within-participants manipulation of recognition vs order memory tests, the pattern of recognition performance was very different from the pattern of recency judgement performance, indicating that semantic similarity had a negative effect on order memory per se. The explanation of the current findings offered by position-based order memory theories is discussed.