Word, Picture, and Mixed-Condition Reality Decisions and Naming: An Investigation of Concept-Based Category Effects

Category Effects 2 The effect of category membership on the processing of both words and pictures was investigated, 'vith special regard to the category interference effect discussed in Kroll and Smith (1989). Response latencies for both decision and naming tasks were evaluated using words-only, picturesonly, and mixed words-and-pictures lists. Comparisons were made between a lists of items from the same conceptual category and a list which was non-categorical. Picture decision, word naming, and object namingthe tasks which, theoretically, require access to the conceptual storeall showed faster RTs for categorical lists than non-categorical ones. The results of these Inmixed conditions support a model of spreading activation providing a category facilitation effect. However, results from mixed conditions (words-and-pictures-together -naming or -decision) were inconclusive, possibly suggesting a category interference effect. Word, Picture, and Mixed-Condition Reality Decisions and Naming: An Investigation of Concept-Based Category Effects Category Effects 3 It is reasonable to think of the primary purpose of the brain as the processing of information. The brain receives various sorts of information from the environment as well as from internal sources like memory, and then uses this information to modulate, control, and direct various forms of behavior, from breathing rates to chess playing. Perhaps the most remarkable information-processing ability of the human brain is that of mental representation; some sorts of perceived information need not be directly connected to a response or to a decision-making faculty, but are instead abstracted in the brain using varying degrees of symbolic representation. This information can then be evaluated, manipulated, or stored according to the characteristic structure of the code in which it is represented. Prime examples of mental representations are the words and structures of languagewords are abstract symbols that can meaningfully correspond to entities in the (internal and external) world, and can be further meaningfully combined through the rules of grammar to represent more complex events, descriptions, and ideas. The other primary modality of mental representation may be a nonverbal, or image(picture-)"based code, as the mind appears capable of holding and manipulating knowledge about the physical forms of objects; this information must be in the form of representationswe surely do this without holding actual trees or chairs in our heads. Although early models of representation relied solely on verbal and nonverbal codes, mental representation is most likely not restricted to just words and pictures. People appear to process both verbal and nonverbal information according to some sort of amodal conceptual knowledge base. Paivio's (1986) dual-code model was based on two simple codes, the verbal and the nonverbal. Concepts did not exist as a separate amodal store; instead, they were manifested in associations between entries on the verbal code. This placed considerable emphasis on the verbal code for conceptual understanding of either words or mental images; to find conceptual information about a visual object, access to the verbal system was necessary. Such verbal activation does not seem necessary to gain conceptual activation about nonverbal entries. To better account for the possibility of conceptual knowledge that was separate and amodal, and thus immediately Category Effects 4 accessible to the nonverbal code without lexical activation, the "conceptual" model was introduced (Kroll and Potter 1984, among others). The conceptual store represents information about entities oeyond that found in their surface forms; for example, the word "chair" and a picture of a chair both relate to the same concept of "chair"; this concept probably includes information about what categories a chair falls into, what they are used for, et cetera. Although considerable debate exists regarding the existence of concepts separate from verbal and nonverbal codes, as well as over the organization of these various mental codes, conceptual models account for the majority of experimental evidence better than the dual-code model, with the further advantage of making more mtuitive sense and elegance. The Model: Relevant Predictions and Evidence In the conceptual model, the verbal and nonverbal codes both have access to a common conceptual base, and this is the sole link between the two codes. The basic form of the model is shown in Figure 1. According to Kroll and Potter (1984), certain predictions can be derived from this model: (1) that tasks requiring access to conceptual knowledge will show similar performance trends, independent of representation modality, (2) that tasks not requiring conceptual activation may reflect different performance trends; these differences reflect differences in the structures of the codes, and (3) that certain tasks which depend on conceptual access may still reflect differences in the mental codes that are also utilized. Kroll and Potter's (1984) research demonstrates that a concept-activating task (making decisions regarding the existence of either words or objects as "real") shows similar results for either words or pictures. A task like naming, however, only requires the activation of lexical information for words. Naming pictures, however, requires access of the lexical form (its name), which can only be reached through the conceptual store. Thus, picture naming requires a trip through the conceptual store, and thus takes significantly more time than word naming. Other tasks in Kroll and Potter (1984), requiring conceptual activation, were still affected by the characteristic structures of the individual codes. Kroll and Potter considered semantic priming effects for pictures and words. Priming existed for both, but there Category Effects 5 was a crucial difference: words frequently found in associative relationships showed a more substantial priming effect than simply related word pairs; for pictures, the priming effect was slightly stronger overall, but insensitive to the type of semantic relationship. This is best accounted for by the manifestation of some information about associational pairing within the verbal code, but which is absent in the nonverbal code. Having established this basic model of the relationships between words, pictures, and concepts in the mind/brain, questions about the organization and functioning of each representational modality may now be examined. The research described here aims to investigate the organization of the conceptual code by evaluating how processing is affected by the activation of a single concept for many items (demonstrating "category" membership) versus the processing of non-categorical lists. Furthermore, it may subsequently shed some light upon the qualities of the verbal and nonverbal codes as each is activated in various ways in various tasks and