Diurnal Variation of Visual Short-term Memory
Short-term memory is an extensively researched topic in cognitive psychology, which has shown the impact of different covariates such as age, gender and time of the day, among others. However, the relation of different covariates have not been studied together, nor are there many studies conducted in which all or most of these confounding factors have been catered for. The current study was conducted to find out whether a definite pattern for the diurnal variation of visual short-term memory exists, if there are any gender based differences in these patterns, and whether the pattern of subjective alertness varies in an inverse relation to the pattern of visual short-term memory. Thirty one first-year undergraduate medical students, between the ages of 17 and 20, were recruited for this purpose. Three memory tests (Digit span test, Picture span test and Corsi block test) were administered to assess their visual short-term memory span, while the subjective alertness was measured using the Stanford Sleepiness scale, at four timings of the day (0830, 1030, 1230, and 1430 hours). The scores of the memory tests revealed a distinct variation pattern of visual short-term memory in both genders. In males, the memory span initially decreased from 0830 to 1030 hours, and then kept on increasing till 1430 hours. In females, on the other hand, the pattern was the same (as in males) up till 1230 hours, but then memory span underwent decay. This pattern, however, turned out to be insignificant. A significant inverse relation was found between visual short-term memory span and the subjective alertness. We propose that a distinct pattern for diurnal variation of visual short-term memory might exist for both genders, but further studies using larger samples should be carried out to confirm this.