Measuring Short Term Memory Span by Investigating the Relationship Between Digital and Spatial Span Tasks.

MEASURING SHORT TERM MEMORY SPAN BY INVESTIGATING THE RELATIONSHIP BETWEEN DIGITAL AND SPATIAL SPAN TASKS.

ABSTRACT

The purpose of this experiment was to measure short term memory span by looking into the relationship between two span tasks: digital and spatial. The experiment measured digit span and spatial span for each participant by carrying out two trials of each task out at the end of which the participants noted their scores down. The participants task was to recall the sequence of the spatial blocks and digits. After the two tasks were completed the correlation between the two tasks and their scores was calculated and the participants memory span was calculated. The results demonstrated that spatial span and digital span tasks had a moderate correlation.

INTRODUCTION

Memory is the ability of the brain to store, retain, and subsequently recall information (wikipedia.org). Memory allows a person to use and recall information when it is most needed. Short--term memory, sometimes referred to as "primary" or "active" memory, is that part of memory which stores a limited amount of information for a limited amount of time (roughly 15-30 seconds). This can be contrasted to long-term memory, in which a seemingly unlimited amount of information is stored indefinitely (wikipedia.org).

The capacity of short term memory is finite. George Miller argued that human short-term memory has a forward memory span of approximately seven items plus or minus two (Miller, 1956). Miller pointed out, going against the trend of the 1950s in order to understand cognition in an information theoretic context that the capacity of short-term memory cannot be measured in terms of a constant amount of information, as expressed in bits. Seven years before Miller, Donald Hebb in 1949 argued that short term memory and long term memory were separate entities and that it was unlikely that any chemical process could occur fast enough to accommodate

immediate memory yet remain stable enough to accommodate

permanent memory. Almost three decades after Hebb argued about the division between short term memory and long term memory McMahon (1982) stated that within short term memory, there are three basic operations: iconic memory, acoustic memory, and working memory. Iconic memory refers to the ability to hold visual images in the short term memory, while acoustic memory refers to the ability to hold sounds in the short term memory. Of the two, acoustic memory can be held longer than iconic memory. On the other hand, working memory is an active process where the goal is not so much to move the information from short term memory to long term memory, but merely to keep it until it is put to use (http://coe.sdsu.edu/eet/articles/stmemory/start.htm).

Atkinson and Shiffrin's multistore model indicated that some or all information from sensory memory is passed on to the short-term memory. The exact mechansims by which this transfer takes place, whether all or only some memories are retained permanently, and indeed the existence of a genuine distinction between the two stores, remain a controversial topic among experts (wikipedia.org).

The span of short-term memory is the number of unrelated letters, one-syllable words or single digit numbers an individual can repeat after seeing or hearing them once and for most individuals it is usually seven. A young German philosopher named Herman Ebbinghaus decided that the best way to study memory processing objectively was to teach himself discrete bits of new knowledge under standardized conditions. Later he would test how well he remembered, again under standardized conditions. To force himself to learn from scratch, Ebbinghuas constructed nonwords, combinations of three letters termed nonsense syllables. He decided to learn ten or twelve of these nonsense syllables in order, as if they represented a string of ideas. (Norman Spear, David Riccio, 1994). Ebbinghaus thought that since participants bring prior knowledge to an experiment this could be an impairing factor. The nonsense syllables would not be known to the participants and and thus any differences in memory for these items under different conditions would represent a genuine property of the memory system. One of the major criticism of Ebbinghaus' experimental work was that it lacked ecological validity, that is it was not true to real life as participants do not learn nonsense syllables.

Smyth and Scholey studied the relationship between articulation time and memory performance in verbal visuospatial tasks. They used several different methods to measure spatial span and digital span and found that the two had a relatively weak correlation of 0.23. The main reason given for this weak correlation was that the output method was different for both tasks and was not consistent through the tasks. This experiment tried to replicate the Smyth and Scholey study by studying the relationship between digit span and spatial span. . This experiment measured digit span and spatial span for each participant by carrying out two trials of each task out at the end of which the participants noted their scores down. The participants task was to recall the sequence of the spatial blocks and digits. After the two tasks were completed the correlation between the two tasks and their scores was calculated and the participants memory span was calculated. In this experiment the correlation between digital span and spatial span was calculated to be 0.79 which is in comparison to the 0.23 in the Smyth and Scholey study which gives us an idea of the extent to which maintaining the same input and output for both tasks affects results.

METHOD

PARTICIPANTS

The participants in this experiment were 20 randomly chosen first year Psychology undergraduate students from the University of Essex. 70 % of the Participants were females and 30 % were males. The mean age in this experiment was 18.5 years.

APPARATUS