Effects of Task Demands on Implicit Memory for Object-Location Associations

Abstract The experiments examined the effect of task demands on implicit and explicit memory for object - location associations. Objects (letters or symbols) were probed one at a time in one of nine locations in a rectangle, and the required task was either location or object naming. Each object was probed in the same location across ten trial blocks and then all the objects changed locations. A decrease in naming times across the first 10 trial blocks followed by an increase in naming times when the objects change locations would indicate priming for the associations. The experiments demonstrated that priming could be obtained when the task engaged, but did not overtax attentional capacity. Explicit memory performance was best when the task did not require much attentional capacity. This paper focuses on implicit and explicit memory for new nonverbal associations. Explicit memory refers to memory for an event which relies on conscious or intentional recollection. Implicit memory refers to memory for an event that is evidenced by a change in performance as a result of prior experience, but which need not be accompanied by conscious or intentional recollection of the prior episode. Although most forms of implicit memory occur across multiple trials, one type of implicit memory, the priming effect, is observed after a single learning trial. Priming refers to a change in the facility with which a stimulus is processed as a result of its recent exposure. The priming effect occurs for both familiar and novel material as long as the stimuli are presented for study singly (e.g., a single word, nonword, or nonverbal stimulus; see Bowers & Schacter, 1993, for a review). When two stimuli are presented simultaneously (e.g., when two words are presented together), such that an association must be formed, associative priming effects have not consistently observed. With normal populations priming of word pair associations has been observed in word stem completion tests after elaborative study tasks, but not after nonelaborative tasks (e.g., Graf & Schacter, 1985; Schacter & Graf, 1986). Goshen - Gottstein and Moscovitch (1995a; 1995b) reported evidence for associative priming using a lexical decision task when there was a perceptual match between study and test environments. However, Musen and Squire (1993a) reported no associative priming in a perceptual identification task. Associative priming effects with memory impaired populations have also been inconsistent. Moscovitch, Winocur, and McLachlan (1986) reported that associative priming was possible using a reading speed paradigm, while other researchers did not find evidence for associative priming (Mayes & Gooding, 1989; Shimamura & Squire, 1989; Musen & Squire, 1993a). The difficulty in obtaining priming for new associations may stem from the fact that the two elements must be unitized into a single item (Graf & Schacter, 1989), and the likelihood of successful unitization may depend on specific stimulus and task situations. Several findings suggest that associations can be more readily learned if elements to be associated are part of the same object (e.g., an association between a color and a shape could appear together as a colored shape). Musen and O'Neill (1994) reported that participants could learn associations between colors and words, and between colors and shapes, when a) the two elements appeared as a single item (i.e., a colored word or colored shape); and b) attention was paid to the association between the two. In contrast, in a study by Treisman (1992), in which the same colored line patterns were studied as in the Musen & O'Neill (1994) study, but color was irrelevant, only pattern priming was observed. Thus, it is possible that priming of the associations requires that attention be paid to both elements, and this unitization process may be facilitated when the two elements to be associated are present in a single object. …