Factors affecting the short-term memory: A pilot study

Short-term memory (STM) refers to the immediate memory in holding information in consciousness. It allows retention of limited amounts of materials over brief intervals. Simple span task has been a dominating experiment to investigate STM processes and individual differences. It elaborates the ability of an individual in immediate recall of a series of discrete stimuli in the correct serial position. 

Total 39 healthy subjects were invited to participate in this pilot study. All participants were determined to be free from the presence of systemic or chronic disease. Consents were obtained from every participant after elaboration of the experimental procedures. The blood pressure and pulse were monitored for subjects throughout whole procedures. Their test items included comparing the length of the words, numbers, similar and different sound of the words.

The correct rate for Numbers was 2.7-fold with a 95% confidence interval ranging from 1.74 to 4.05, which was significantly higher than that for Letters that sound different (p = 0.0005). The correct rate for Numbers was 2.4-fold with a 95% confidence interval ranging from 1.60 to 3.73 which was higher than that for Letters that sound alike (p = 0.0003). The other two tested items of short and long words when compared with Numbers also showed a significant difference (p = 0.05). However, their odds ratios were not higher than the Number. The Pearson Chi-squared test for the rest of groups yielded no statistically significant difference among them. This result showed that Numbers were easiest to be remembered.

Regarding the individual differences, age, sex and educational level were unable to acquire statistical significance. To a certain extent, this study failed to obtain the ageing effect on span performance documented. Increasing sample size and recruitment of older participants (>65 years old) were considered in the future study.