Faculty Mentor

Debra Spear


The present study examined differences in accuracy of responses to serial and concurrent stimuli in an immediate free recall task for individuals from chemistry and psychology courses. Average accuracy of responses for presentation order, stimulus type, and gender differences were measured. The procedure used Superlab 4.0 and consisted of one practice trial followed by eight recorded trials of serial and concurrent word lists. Counterbalancing was used to try to control learning of one order of presentation over the opposite order. Serial word lists consisted of ten words presented two seconds apart and one at a time. Concurrent lists consisted of ten words presented simultaneously for twenty seconds. No significant main effects of presentation order, stimulus type, or gender were found when calculating a mixed ANOVA. No gender differences in accuracy between the two types of stimuli were expected. There were also no significant effects of the interactions for these variables. However, a medium effect was found for the interaction of presentation order and stimulus type. Increasing the population may lead to a significant effect of the presentation order by stimulus type interaction. Immediate free recall (IFR) is a common method used to try to determine individual differences in the number of stimuli (usually words) that can be stored in working (short-term) memory (Bhatarah, Ward, Smith & Hayes, 2009; Huang, Tomasini & Nikl, 1977; Seiler & Engelkamp, 2003; Ward & Maylor, 2005). Most often, a recall task involves participants presented with a given number of words in a serial presentation. Presentation of this format is a specific word, followed every one or two seconds by each consecutive word, until the list is complete (Bhatarah et al, 2009; Matlin, 1976). Stimuli presentation is either oral or visual depending on the procedure (Baumeister & Luszcz, 1976; Ozubko & Joordens, 2007). IFR is employed promptly following the final stimulus. According to Laming (2009), the recall task regularly occurs for one minute; and at this time, individuals write down or verbally list as many items as they can remember (Russo & Grammatopoulou, 2003; Smith, Jones & Broadbent, 1981). This provides the measurement of recall as number of items remembered, or accuracy of recall. According to current theory, working memory consists of a system that briefly stores and processes information from the environment, from long-term memory, as well as maintaining and altering stimuli that are still currently in the system itself (Gazzaniga, Ivry & Mangun, 2009). The phonological loop is one aspect of the working memory system and its main function is the encoding and rehearsal of stimuli such as words. Verbal stimuli, rehearsed or processed by the phonological loop, may stay in the working memory system, or may be processed and stored in long-term memory. IFR procedures record the number of words processed and subvocally rehearsed in the phonological loop (Campoy, 2008). The words at the beginning of the list tend to be encoded in long-term memory and the most recent words in the list are thought to be present in the short-term store, or working memory. Accuracy of recall, the number of items correctly recalled, using serial presentation of stimuli, spans most of the literature over the past forty years (Campoy, 2008; Haist, Shimamura & Squire, 1992; Joseph, McKay & Joseph, 1982; Matlin, 1976). Students make up the participants in many of the studies by performing serial presentation recall tasks (Bhatarah et al, 2009; Seiler & Engelkamp, 2003; Ward & Tan, 2004). Serial presentation of IFR is used to test accuracy of individuals’ working memory; concurrent presentation, in a similar manner, is useful for the same reason. Very few recall tests include concurrent presentation of stimuli (Harness, Jacot, Scherf, White & Warnick, 2008; Sneed, Brunts, Mueller, 1977). This method presents all the stimulus words simultaneously to the participants. Once the stimulus exposure period ends, individuals perform the recall task as they would in serial presentation formats. Concurrent presentation recall procedures have been used to compare recall accuracy of schizophrenic populations versus healthy subjects (Brebion, David, Bressan & Pilowsky, 2006). It was found that healthy subjects did have increased accuracy in the free recall task. Concurrent lists, presenting all the words at the same time, may lead to many words being processed into the long-term store, or may allow more words to remain in short-term memory. Some studies suggest that concurrent presentation is believed to lead to diminished accuracy of items recalled in comparison to serial presentation. (Hoppe, Stojanovic, Karg Foundation Young Researchers Group 2008/09, & Elger, 2009). Sneed, Brunts, and Mueller (1977) found that concurrent lists of more than two words decreased performance in free recall. Theoretically, this is due to less ability to process single words in a concurrent list because the individual will instead process that list as a „chunk,’ in which case the entirety of the list can be one single stimulus, as well as a few words, or even just one word. Other research has shown that the availability of more words can also lead to increased recall stemming from the ability to make more chunks from a larger set of words, leading to recalling more words in the list (Chen & Cowan, 2005; Miller, 1956). It is also possible that one chunk can even cue the participant for the next chunk in a list, further increasing the likelihood of recalling more words (2005). The present study aims to determine if format of presentation alters the number of items remembered for each individual. If there is a difference between the accuracy of responses to each presentation, this may lead to increased understanding of the working memory model. If concurrent presentation of stimuli leads to an increased number of accurate responses, it is possible that the list presenting all the stimuli simultaneously allows individuals to process more words and move them into long-term memory. Participants will recall eight lists of words in concurrent presentation and eight lists in serial presentation. Counterbalancing of each presentation type, by switching around the order of presentation, should help counteract learning of one presentation over the other, if accuracy of recalled items increases temporally. This study does not employ the use of distractors between serial presentation stimuli. This allows for performance of chunking in both presentations. Participants can also covertly rehearse words from the lists. Covert rehearsal is the process of practicing the words without orally reciting them. Chunking and covert rehearsal are two of the main strategies used to remember words in a recall task (Eagle, 1967). Accuracy will be determined by the number of items recalled that are perfect matches. Differences in accuracy of items recalled for concurrent compared to serial presentation of stimuli for individuals is the focus of this paper. The effects of stimulus type are expected to alter accuracy. However, it is not clear whether concurrent or serial presentation will lead to increased accuracy. Order of presentation will also be reported. It is expected that as individuals proceed through the serial and concurrent presentation tasks, some learning will occur and items remembered will increase over time for both stimuli presentations for all individuals. As mentioned earlier, counterbalancing will control for learning of the presentation types in a specific order. As a quasi-experimental variable, gender differences in accuracy of items recalled shall be examined. There is expected to be no difference between the accuracy scores of men and women.

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