Accounting For Improved Memory After Timed Delays - Essay Example

? Consolidation versus Rehearsal in Working Memory: Accounting for Improved Memory after Timed Delays Human memory has been a matter of debate and research for a long time, and a number of theories have been suggested to explain the mechanism by which information is committed to memory. Two hypotheses have been suggested to explain how data is stored in short term memory – the rehearsal effect and the consolidation theory. This study attempted to verify which of these proposals receive more support from empirical data, and thus, used data collected from 57 persons to asses whether people were more accurate and fast in their responses when allowed to consolidate information or rehearse it. The data provides some direct evidence for the consolidation theory, but none for the rehearsal theory. The implications and limitations are discussed, with an emphasis on more detailed research to follow on these results. Consolidation versus Rehearsal in Working Memory: Accounting for Improved Memory after Timed Delays Introduction Psychologists have always been fascinated with understanding the way our brains process and store information, and the mechanisms by which we retrieve this information from the different memory stores. Traditional distinctions between memory stores suggest the presence of sensory memory stores, a short term store and a long term store. While sensory memory is supposed to retain some information for only a few seconds at most, and the short term memory (STM) retains a few units of information for about half a minute or so; the long term memory store has the capacity to retain a vast amount of information for a very long period of time (Robinson-Riegler & Robinson-Riegler, 2008). The short term storage – which has been prominently studied – may also be understood through Baddeley and Hitch’s (1974) multi-component model called the Working Memory. They describe this system as having specialized components that deal with different kinds of information and as being responsible for storing and processing information simultaneously (Baddeley & Hitch, 1974). A number of theorists have tried to explain the process by which information is committed to the different memory stores and the problems that people encounter in the process of doing so. The process by which people commit information to STM has been studied in great detail; particularly since this process has valuable applications to everyday life (Robinson-Riegler & Robinson-Riegler, 2008). One theory proposes that information is committed to STM through rehearsal of material (Craik & Watkins, 1973). According to the rehearsal effect, people quickly rehearse information phonologically when they get a chance during attention demanding tasks in a bid to maintain the information (Camos, Mora & Oberauer, 2010). A typical example of this process is when a person who wants to copy an address will repeat it to themselves a few times while they write it down. Evidence for the phonetic nature of information associated with rehearsal comes from studied like the one conducted by Camos, Mora and Oberauer (2010) which show that rehearsal can be inhibited in the presence of phonetically similar items. This study also found that phonologically similar items affected memory when other processing tasks were involved, indicating that rehearsal required cognitive resources. Barroillet, Bernardin, and Camos (2004) suggest that time related decay occurs from STM because other tasks that demand attention and cognitive resources that are required for information maintenance. The study findings demonstrate that when an individual had fewer tasks in the interval between units of information, they were able to commit more information to memory as compared to those who completed more tasks. Typical rehearsal studies use articulatory suppression (AS) tasks that inhibit the verbal rehearsal of information. AS tasks use repetitive, irrelevant speech units to prevent rehearsing of pertinent information (Baddeley, Lewis, & Vallar, 1984). According to Neath, Farley and Surprenant (2003), the use of AS tasks prevented the individual from using auditory cues to encode the information by rehearsing it. Thus, the information trace decays since it cannot be attended to. A more recent approach to memory suggests that information is committed to short term memory through a process called consolidation (Joliceour & Dell’Acqua, 1998). According to this theory, information from perceptual memory is processed and thus transferred into STM through a process called short-term consolidation (STC) (Joliceour & Dell’Acqua, 1998). Evidence for this effect is found in tasks that required speeded simple decision making at different points after the presentation of a letter stimulus that was to e encoded to memory. Joliceour and Dell’Aqua (1998) found that decision making tasks presented immediately after the letter was exposed were associated with slower response timings as compared to those presented after a delay, suggesting that cognitive resources are unavailable initially since they are being used for consolidation. There is also evidence that immediate presentation of processing tasks can affect the process of consolidation, and may disrupt it. Woodman and Vogel (2005) found that better memory was associated with conditions that allowed for consolidation by providing longer inter-stimulus delays, whereas immediate presentation tasks were associated with lower recall rates. Consolidation theory has slowly gained popularity due to its applicability to a wider variety of more realistic settings as compared to the rehearsal theory. Working memory (WM) is a limited capacity system, and can process only a few units of information at a time (Robinson-Riegler & Robinson-Riegler, 2008). It seems evident that failure to commit information to short term memory occurs due to inadequate encoding, whether through lack of rehearsal or inadequate opportunity for consolidation. Competing demands on the limited cognitive resources of the working memory may be the reason this lack of encoding, which often appear as disruptions and interruptions (Wixted, 2005). The present study attempts to determine if consolidation or rehearsal are associated with committing information to STM. Thus, it is expected that all participants will exhibit better memory and faster reaction time for the delayed condition. If both groups show similar improvement in performance in the delayed condition, the consolidation theory will be supported, while if only the non-AS group shows improvement, rehearsal theory will be supported. Based on these premises, the following hypotheses were proposed to test both theories: Consolidation: Participants will have better memory performance scores in the delay condition than in the immediate condition, overall. Participants will have quicker reaction times in the delay condition than in the immediate condition, overall. Rehearsal: Only Participants in the delay condition of the non-AS group will have better memory performance scores than in the immediate condition. Only Participants in the delay condition of the non-AS group will have faster reaction times than in the immediate condition. Method Variables and Design The study had two independent variables and two dependent variables. The first independent variable was presence of AS which had two levels and was an independent measure. The first level was use of AS and the second level was no use of AS in any trial. The second independent variable was rate of presentation which also had two levels and was a repeated measure. The first level was immediate presentation and the second was delayed presentation. Each participant was exposed to both levels of this variable. The first dependent variable was accuracy of response which was measured by the extent to which a participant was able to recognize the target stimuli correctly. The second dependent variable was speed of response; which was measured by the speed with which participants responded correctly. The study had a mixed factorial design so that for each dependent variable, a 2 x 2 mixed factorial design was used. Participants Sixty four participants took part in this study voluntarily. Participants were aged 18 and 60 with a mean age of 30.8 years. 44 of these were female participants while 20 were male. After analyzing the data, it was found that 7 participants had failed to attend to the tasks adequately; and thus the data for these participants was removed from the analysis. Apparatus The entire testing session for each participant was conducted using computers and particular software designed for this experiment. Each participant was presented with a blue screen with a number of boxes arranged on it. The target stimuli were presented in the central white box. Target stimuli included the to-be-remembered (TBR) alphabets C, J, F, H, L, M, N, P, Q, R, S and X and the processing task numbers from one to nine (excluding five). The 12 letters were chosen as they are all consonants that are similar in frequency of use based on Joliceour and Dell’Aqua’s (1998) experiments. Two blue boxes labeled “above” and “below” were presented above and beneath the central box respectively and two red boxes labeled “odd” and “even” were presented to the left and right of the central box respectively. These boxes and the numbers were used for the intervening processing tasks. Procedure Once informed consent was taken from participants, they were seated independently at the testing computers. All participants were provided with instructions on the computer screen that informed them about the stimuli and the use of the different boxes. Participants were instructed to say the TBR alphabets aloud when they were presented. Participants in the AS condition were asked to follow this by saying the word “Monday” repeatedly until the next alphabet was presented. Time taken by participants to complete the experiment was approximately 40 minutes. For each participant, stimuli were presented in two blocks – one for the immediate condition in which the processing task followed the target task immediately, and one for the delayed condition where the processing task was completed after a short delay. A break was provided between the two blocks. Each block contained 16 trails of one minute each. Each trial contained five TBR letters followed by the recognition task. Each block was also preceded by a set of four practice trails. The recognition task required the participant to choose the presented TBR alphabets in the correct sequence. Both accuracy and speed of response were calculated. Data was collected on two processing activities, correct decision of whether a given digit is odd or even (by choosing the red boxes) and whether the digit is above or below the digit five (using the blue boxes). These tasks were each presented for eight consecutive trials within each block, and were counterbalanced across subjects. Results The study collected data on 64 participants, but after analysis, it was found that some participants had not completed the task adequately, and thus, the data on these participants was removed. The data was studied afresh, and it was found that in the immediate condition, the new mean overall accuracy score was 49.67(S.D.15.4) while the mean reaction time was 1427.60(S.D. 259.06) ms. The new mean correct processing items were 59.67(S.D.4.3). In the delayed condition, the new mean overall accuracy score was 49.98(S.D.15.10) while the mean reaction time was 1239.019(S.D. 211.62) ms. The new mean correct processing items were 61.35(S.D.3.7). Since there were two independent variables with 2 levels each, and one of the factors was repeated; a mixed measures ANOVA was deemed an appropriate test to use. The test was conducted using the SPSS package, and different ANOVA statistics were computed for each dependent variable. In was found that for the dependent variable of accuracy of responses, the main factor of rate of presentation showed no significant effect [F (1, 55) = 0.122; ns]. The main factor of use of AS did produce a significant difference [F (1, 55) = 70.04; p < 0.001], while the interaction was also not significant [F (1, 55) = 1.376; ns]. The graph for the data with respect to the dependent variable of accuracy is presented in figure 1. Figure 1: Data on accuracy of performance in both groups The main effect of the rate of presentation on the overall response time was significant [F (1, 55) = 89.15; p < 0.001]. The main effect for the presence of AS was not significant [F (1, 55) = 2.69; ns] while the interaction effect was significant [F (1, 55) = 6.169; p < 0.01] for overall reaction time. For the correct responses for processing tasks, the main effect for the rate of presentation was significant [F (1, 55) = 7.94; p < 0.01]. The main effect for the presence of AS was also significant [F (1, 55) = 9.17; p < 0.01] while the interaction was not significant [F (1, 55) = 0.231; ns]. The graph for the dependent variable of reaction time is presented in figure 2. Figure 2: Data on response speed in both groups T-tests were conducted as a post hoc analysis to verify the differences in reaction time between immediate and delayed conditions in both groups of participants. Both t-tests were significant, showing that participants were faster in the delayed condition as compared to the immediate condition in both AS and non-AS conditions. The t-test value for the AS condition was 7.49(p Read More