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People are able to respond more quickly to stimuli following a recent encounter with those same items. This facilitation in processing a stimulus as a function of a prior encounter is known as repetition priming. This thesis contains eleven experiments that attempt to describe the nature of the representations in memory underlying the effect. Changing aspects of the stimuli and task between the initial encounter and the subsequent test encounter allow examination of the kinds of information contained in these representations. The effects on repetition priming of recombining the pairings of simultaneously presented items in a speeded same/different matching task were examined (Experiments 1,2, 3 & 6). Despite priming being insensitive to the pairings of items, subjects were able to recognise this information (Experiment 4), revealing an item-specific locus for the priming effect and a dissociation from explicit memory. Priming was shown to be based on domain- specific and not conceptual information (Experiment 5). Experiments 7 and 8 examined the role of repeating the decision and response to stimuli in producing repetition priming. Results suggested that any such role reflects subjects' use of explicit memory as a basis for responding in the task, rather than reflecting automatic priming effects. Manipulating the semantic interpretation demanded of a homograph between training and test did not affect repetition priming (Experiment 9). The independent representation of simultaneously presented stimuli did not necessarily depend upon the activation of pre-existing representations or connections (Experiment 10). Experiment 11 revealed a necessary role for the identification of stimuli in producing repetition priming. The results of these eleven experiments pose problems for accounts of repetition priming based on the retrieval of processing episodes, or the reinstatement of processing demands. The results are consistent with a perceptual locus of the priming effect, based on representations of structure and form employed in the identification of individual stimuli.

How context affects memory is the central focus of the six experiments making up this PhD thesis. In these experiments, pictures of faces were presented in an incidental encoding phase, paired with a variety of indoor and outdoor context scenes (e.g., park, supermarket, swimming pool), and a recognition memory test ensued in which faces were paired with either the same context (exact same context the face was paired with at encoding), switched context (a context that was presented at study, but not presented with that particular face), or new context (a context never before seen), relative to encoding. In Experiment 1, the importance of instructions at encoding was examined by manipulating instructions to either actively link or passively view the face and context at encoding. Maintaining the same context as at encoding reliably enhanced overall detection, and recollection, of studied faces relative to a new context, replicating the known context reinstatement (CR) effect. There was also a reliable memory benefit for faces paired at test with the same relative to a switched context, indicating a context specificity (CS) effect on memory. Encoding instructions to either actively link, or passively view, face-context pairs during encoding did not influence the presence or magnitude of the CR or CS effects, suggesting that linking of target + context may occur spontaneously. In Experiment 2, dividing attention did not influence CR, but did eliminate the CS effect on overall memory. Findings suggest that the general boost to memory from reinstating an old relative to a totally new context at test is robust, though linking specific contexts to targets is hampered when attention is limited during encoding. In Experiments 3 and 4, familiarity of the face to the observer interacted with context effects. In Experiment 3, face familiarity was manipulated by presenting famous versus non-famous faces during encoding and an attenuated CR effect was observed for famous relative to non-famous (unfamiliar) faces, though CS remained. In Experiment 4, degree of familiarity was controlled by pre-exposing the study faces 0, 1, 3, or 10 times prior to the study phase. After just one pre-exposure to an unfamiliar face, the CR effect was reduced. Experiment 5 examined whether distinctive faces were less susceptible to context effects relative to similarly familiar, but less distinctive, faces. CR and CS effects were predicted for out-group faces (Caucasian faces for Asian participants and Asian faces for Caucasian participants), and a reduction in both CR and CS for in-group faces (Caucasian faces for Caucasian participants and Asian faces for Asian participants). Results indicated no difference in CR or CS across the conditions, suggesting that distinctiveness may not be an important factor in mediating context effects. The final experiment examined how the expectancy of a face + context pairing influenced CR and CS effects, even when the target face was familiar. There were robust CR and CS effects for faces when these were repeatedly paired with a specific context during study, but a loss of both effects when faces were paired with varying contexts during study. Results extend our current knowledge regarding the role of context in memory and supports memory models that suggest context information presented at test acts as a cue that uniquely specifies a particular target.

Abstract A model for free recall of words is presented and applied to representative free-recall experiments. According to the model, a subject's lexicon contains a representation for each word and for the association between each pair of words. Studying a word in a list strengthens that word's representation in the lexicon, but reduces the strength of previously studied words. In addition, while studying the list, the subject associates pairs of items and, thereby, strengthens the corresponding associations in the lexicon. A subject's efficiency at forming associations drops off as the number of pairs increases. Retrieval is initiated with a report cue. Selection of an item for report is based on its strength in the lexicon plus the strength of its association with the retrieval cue. Selecting an item for report changes the strength of its association with the cue in the lexicon. To test the model, parameters were obtained by fitting it to serial-position curves taken from the archival literature. The model predicted three additional dependent measures: order of report, items correct per trial, and the number of intrusions per trial. In addition, I applied the model to phenomena associated with the free-recall task and showed that it captures the list-strength effect, interference in part-list cuing, clustering with categorized lists, and distraction effects. The model itself does not change to capture these experimental data. Word lists are presented to the model according to the experimental protocol used in the original experiments, and the model captures output measures derived from the experimental data. The model demonstrates that simple mechanisms can capture a wide range of apparently complex behaviour if we allow for a large enough knowledge base. In effect, the complexity of behaviour in free-recall paradigms lies in the interactions in the lexicon, not in the complexity of the recall mechanisms. / Thesis (Ph.D, Psychology) -- Queen's University, 2013-01-28 14:12:49.99