In cognitive psychology, memory has been defined has the mental framework which encodes, stores and retrieves necessary information whenever required. Classically, memory has been broadly classified in two categories - sensory/short term memory and long term memory. As the name suggests, the former temporarily stores information while the latter is supposed to hold memories of the past. It was stated that our attention processes are associated with the short term memory and also there have been studies to show that there is a limitation on the storage capacity ( chunks of 7 ) in the short term memory. However, almost no details were available about the information processing mechanism in sensory memory. This led to subsequent research and a new model was proposed by Baddeley and Hitch which essentially replaced short term memory with a new phrase-working memory. The new model proposed three major components for the working memory - the central-executive or the Attention controller and the two subsidiary systems - the phonological loop, responsible for verbal and speech acquisition and the visuospatial loop, responsible for storing information related to spatial and visual domain. Thus working memory was now identified as the prime agent responsible for our perceptual cognition and subsequent processing and maintainence of the stimuli around us. Earlier, the working memory and the long term memory were considered to be seperate entities. However with subsequent research in this area, it was observed that patients with phonological deficits in the working memory were found to be slightly inefficient in their long term verbal learning also. This and other findings led to the proposal of a fourth component of the working memory namely - episodic buffer by Baddeley and Hitch in the year 2000. This buffer is a limited-storage system, controlled by the central executive, which serves to assimilate information from various sources and form coherent episodic constructs required for long term learning.
In order to understand the complex processes of cognition, there have been many research debates in the field of working memory on areas such as differences in the nature of short term and long term memory, exact working of the central executive, binding of representations of different components of the working memory into one coherent form and the role of working memory in controlling action. With reference to cognition, braodly two kinds of memory tasks have been studied - simple span tasks which are restricted to domain specific loops responsible for temporary storage or processing of information and complex span tasks which are essentially controlled by the domain-independent central executive and are related to our higher cognitive functions such as comprehension, reading and language learning. For example, a reading span task would involve determing the truth of the sentence ( processing ) and storing the final word of each sentences ( memory maintainence ). Thus, the central executive has to serve two fold function - controlling attention to goal-specific information and processing it even in the face of external distraction. This brings us to the concept of proactive interference in which previous information in our memory limits our retrieval and processing abilities. "For example, when learning lists of words the first list will be relatively easy to recall but subsequent lists become increasingly more difficult to recall because words from previous lists will interfere with the retrieval of current list items" (Kane & Engle, 2000; Keppel & Underwood, 1962). However, in this context it has been argued that by increasing the number of trials, practice over a period of time tends to compete with the PI inhibition and therby improves recall in some cases. In one of the studies, it was suggested that for younger subjects, the effect of practice outscored the effect of PI in determining the WM performance( May et al.,1999, and Lustig et al., 2001 ). In older adults, however opposite was true because of age-specific retardation in inhibitory control ( Rowe, Hasher, & Turcotte, 2009). Lutig and others proposed that in low PI condition, there is no correlation between WM span recall and higher cognitive functions such as fluid intelligence. In high PI condition, when the situation gets taxing individual differnces in responses based on fluid intelligence are observed.
All the aforementioned research , which examined the effect of practice and proactive interference on wm performance and higher cognitive functions, was conducted mostly for the verbal tasks. However if the functionality of central-executive is domain-independent, then it should be applicable to the visuospatial domain as well. Therefore I intend to examine the effects of PI and practice in visuospatial working memory. Visuospatial skectchpad as a link between the spatial and the visual channels of information. It also serves to bind any visual stream with motor or tactile codes. In the following experiment, a pair of stimuli - a mental processing task and a memory maintainence task will be presented consecutively and the responses will be recorded. For the low interference condition, a relaxing stimuli will be provided in between trials to prevent taxing of the central executive by excessive information. On contrary, in the high PI condition, no relaxi stimuli will be provided and the trials will continue one after the other. It is to be noted that counter-intuitively, interference builds up when similar kind of stimuli are provided continuously and not when dissimilar information is provided. The objective of the experiment can be summarised as follows:
1. To study the simultaneous and individual effects of PI and practice on Visuospatial tasks.
2. To study how the influence of practice affects the performance in different PI conditions.
1. Stimuli
2. Procedure
In the experiment there will be three rounds of 4 trials each. Each trial will randomly consist of 2 to 5 set of stimuli. Each trial will be followed by either a low-PI or high-PI condition. In each trial the mental rotation task and the memory maintainence task will be presented sequentially. In the mental rotation task the subjects have to identify if the character has mirror reversed or normal orientation. The response time will be noted at this stage. Next the matrix with one of its 16 squares blackened will be presented for some period of time ( say 2 sec ). At the end of 1 trial ( consisting of 2-5 length ), the subjects will be asked to sequentially point out the locations on the matrix. Then in the low PI condition, there will be a span of 15-20 secs gap in which priming task of symbol comparison will be introduced. Arbitrary set of symbols will be presented on either side of the center line of the screen and the subjects will be asked to respond if the order of characters is same. This process will be repeated for 6-8 times after each trial. In the high-PI condition the participants will automatically start the next trial without any break. No priming stimuli will be presented after the end of each round. Participants will be asked to remember the position of the filled squares and also maintain the accuracy of response in the mental processing task.
3. Dependent Variables in the Experiment
i). Response time for the processing task
ii). % correct recall in the memory maintainence task after each trial
4. Possible Observations
i). Individaual effect of practice on response time over increasing no of trials.
ii). Individual effect of practice on the span tasks over increasing no of trials.
iii). Individual effects of PI condition on recall scores and the response time.
iv). Simultaneous effect of practice and PI on the working memory span task.
v). Influence of practice and PI conditons on each other.
ANOVA (Analysis of variances) will be used for calculating the correlation between various variables.
4. Challenges
The major challenge is to designing the experiment set-up which accurately records the response time and maintains the spontaineity and continuity of the experiments. Either of E-prime, PsychoPY or MS-powerpoint will be used to set up the stimuli.
4. Possible extension in the Project
i). Different age groups can be expeimented upon to compare the effects of practice and PI as dependent on age.
ii). If time permits, similar proceedure could be used for verbal and verbal-cum-visuospatial memory to compare results across different domains of working memory.
Verbal stimuli - grammatical correctness of sentences (Processing task), recalling the last word of each sentence in a paragraph (Memory maintainence task)
Stumuli for verbal-cum-visuospatial memory - an incomplete sentence with prepostions to be filled from a group of prepositions (Processing task), recalling keypad leeters (maintainence task)
1. Alan Baddeley Nov 2000. The episodic buffer: a new component of working memory? Trends in Cognitive Sciences.
2. Alan Baddeley June 2002. Is Working Memory Still Working? European Psychologist.
3. Blalock & McCabe 2011. Proactive interference and practice effects in visuospatial working memory span task performance.Memory.
4. Engle, R. W., & Kane, M. J. (2004). Executive attention, working memory, capacity, and a two-factor theory of cognitive control.
5. Kane, M. J., & Engle, R. W. (2000). Working-memory capacity, proactive interference, and divided attention: Limits on long-term memory retrieval. Journal
of Experimental Psychology: Learning, & Memory,
Cognition
7. Lustig, C., May, C. P., & Hasher, L. (2001).Working memory span and the role of proactive interference. Journal of Experimental Psychology.
May, C. P., Hasher, L., & Kane, M. J. (1999). The role of interference in memory span. Memory & Cognition
8. Redick, Broadway, Meier, Randall W. Engl. Measuring Working Memory Capacity with Automated Complex Span Tasks.
9. Rowe, G., Hasher, L., & Turcotte, J. (2009). Age and synchrony effects in visuospatial working memory.The Quarterly Journal of Experimental Psychology.