Implicit And Explicit Memory Test Specific Effects

Over the past 30 years, the concreteness effect has been one of the most robust findings in the memory literature. Word concreteness refers to the extent to which one can readily form a mental image of a word's referent. The concreteness effect refers to the finding that concrete words have an advantage over abstract words in recall, recognition, lexical decision, pronunciation, and comprehension. Several theories have been developed to explain the concreteness effects, the most prominent of which is the dual-code theory proposed by Paivio (1971,1991). According to this theory, there are two distinct coding processes, a verbal or linguistic code and a nonverbal or imaginal code. Concrete words are assumed to be processed in both codes, whereas abstract words are processed primarily in the verbal code. It is the availability of two codes at retrieval for the concrete words relative to only one code for the abstract words that is responsible for producing the superior memory for concrete items. Within the dual-code hypothesis, two other effects on memory, that is to say, the imagery effect(Imaging the referent of a word produces better retention than nonimaged words.) and the picture superiority effect (Pictures are recalled or recognized better than words.), are presumed to share a common mechanism with the concreteness effect. Specifically, the activations of dual codes in the encoding of concrete words, the imagery instructions and the picture processing enhance the performance for these items. Paivio also argued that the activation of two codes requires referential processing which is conceptual in nature. As such, all the three effects may be considered as conceptually driven effects on memory.The concreteness effect, the imagery effect, and the picture superiority effect have been well established in many researches using traditional tasks ( explicit memory tests ). However, these three effects on implicit tests appear to be less clear and discrepant. According to the transfer appropriate processing framework advanced by Roediger and colleagues to explain the dissociation between implicit and explicit memory tests, conceptual variables should affect performance on a conceptual task. Thus, based on the assumed role of referential processing, all three effects should emerge on memory tests that are classified as conceptual tests, both explicit andimplicit. The prediction was confirmed in studies on imagery effect ( Blaxton,1989; Nyberg & Nilson,1995; Wippich & Mecklenbrauker.1995; Hamilton & Rajaram, 2001). And yet, with respect to the picture superiority effect and the concreteness effect, researchers failed to find the two effects on conceptual implicit memory tests (Weldon & Coyote, 1996; McDermott & Roediger,1996; Hamilton & Rajaram,2001), which raised questions for the processing framework and the dual-code hypothesis. In order to explore the reasons for these findings, some researchers suggested that it was essential to seek interpretation elsewhere. Weldon and Coyote (1996) postulated the visual distinctiveness hypothesis to account for the picture superiority effect in explicit memory, while Hamilton and Rajaram (2001) argued that conceptual processing was greater in magnitude during imaging than during the encoding of concrete words, so imaging enhanced conceptual priming but concrete words did not. Nevertheless, these ideas are not sufficient to explain all the data. The present study was motivated by the discrepancies mentioned above. To our knowledge, there are very few contrastive researches on the concreteness effect on implicit and explicit memory tests. Thus, many factors are worth further exploration. The aim in this thesis is to investigate the effect of word concreteness on the performance on conceptual memory tests so as to test the processing framework, the dual-code theory and the visual distinctiveness hypothesis.Three experiments were presented in this study. Experiment 1 investigated whether there are concreteness effects in recognition and preference decision by manipulating word f...