| Implicit memory is revealed by indirect (i.e., priming) tests which do not necessitate effortful retrieval. In priming, an increase in processing efficiency is measured for a previously encountered stimulus or concept. In cross-form identity priming (CFIP), stimulus form is varied from study to test. CFIP reflects conceptual implicit memory because only the conceptual identity denoted by the stimulus is repeated between prime and target.; Motivated by an evolutionary perspective, we used a CFIP paradigm (picture-to-word priming) to investigate whether variables known to impact on explicit and semantic memory would also impact on the strength of implicit memory. Based on findings of category-specific semantic memory impairments recorded among brain-damaged patients, in Study #1, we examined whether items from the domain of living things would show greater CFIP than nonliving items. A separate line of research has shown that long-term memory is enhanced for emotionally salient events or stimuli. In light of this data, we investigated, in Study #2, whether emotional salience would impact on the magnitude of CFIP. Finally, in Study #3, we investigated the neural underpinnings of subliminal CFIP using fMRI.; Study #1 revealed that items belonging to the “living” category led to greater CFIP. This finding is in line with the assumption that the semantic system is particularly tuned to the identification and processing of “living” things. One interpretation of this effect is that the living items were more deeply processed, possibly because of their increased emotional salience. Study #2 revealed greater CFIP for emotionally negative versus emotionally neutral or positive stimuli. We posit that this difference may be related to spontaneously deeper processing for negative items because they are more likely to conjure real-world items or situations which could be dangerous to the observer. Study #3 found significant subliminal CFIP in a paradigm which eliminates the risk of contamination by explicit memory. Behavioral results bolster claims that unconsciously perceived stimuli can be deeply processed. FMRI results reveal that areas known to be involved in semantic processing (bilateral occipitotemporal and the left anterior superior temporal cortex) play a role in subliminal CFIP. Theoretically, our CFIP results support activational accounts of priming. |
