The Effect of Distractor Intervals on Short-Term Memory Retention

The Effect of Distractor Intervals on Short-Term Memory Retention

Umer Hassan

Queens College - CUNY

Abstract

This experiment investigated if prevention of rehearsal at different time intervals affected stimulus retention in short-term memory. Interference often causes disturbance in short-term memory retention. Previous research has studied the capacity and duration of short-term memory on different age groups. Our hypothesis is the distractor task will have an effect on short-term memory capacity as measured in percent recall. We expect the longer the distractor task - the lower the percent recall. 22 young adult students were shown trigrams at three different time intervals - 1, 11, and 21 seconds and were asked to recall the trigrams after a word/nonword distractor task. Contrary to the hypothesis, there was no significant difference found in percent recall between the three distractor intervals. We were unable to replicate the findings of our previous experiments given the context we used. This could be due to an imperfect design due to a not distracting enough task, participant's prior knowledge and variation of test settings.

The Effect of Distractor Intervals on Short-Term Memory Retention

Short-term memory refers to memories which last for a few seconds or minutes. Short-term memory is of limited capacity and differs slightly in different humans. Beyond this capacity, new information can "bump" out other items from short-term memory. Interference often causes disturbance in short-term memory retention. This accounts for the desire to complete the tasks held in short term memory as soon as possible. Often we have to consistently re-expose ourselves to the information. Memories are so volatile that we have to repeat to remember. Objects in short-term memory can be of vital importance because it impacts our everyday lives. Thus, short-term memory is very crucial to be studied. Previous research has studied the capacity and duration of short-term memory on different age groups. The focus of the current research is to expand upon previous studies and to determine if distractor tasks affect short-term memory among the same age group.

Brown (1958) conducted experiments to study the hypothesis of decay of memory trace as a cause of forgetting. The experiments sought to study memory over a period of few seconds when only a single presentation of the material had been given. Immediate memory was studied in the experiments. On each trial two sets of stimuli were presented in immediate succession. The subject was instructed to read out the stimuli of the first set. The required stimuli consisted of consonants and the additional stimuli consisted of digits or consonants. The required stimuli were shown in black and the additional stimuli red. A control condition was also used with no additional stimuli presented. Intervals were changed through the three experiments. The results of the individual experiments fit with the hypothesis of rapid decay of the memory trace. A delay of several seconds before recall produced considerable forgetting. In Experiment 2, when additional stimuli intervened before recall - the similarity to the required stimuli was of minor importance in determining the amount of interference produced. When they preceded the required stimuli - the interference was slight. In Experiment 3, the effect of additional stimuli before recall remained considerable even when there was interval of several seconds between presentation of required and additional stimuli.

Bherer, Belleville, and Peretz (2001) studied the effects of education level and age on short-term memory using the Brown-Peterson task. The performance of 24 young (mean age 25.8 years) and 24 elderly (mean age 67.2 years) persons were compared on an adapted version of the Brown-Peterson procedure. Participants were asked to report consonant trigrams after variable time periods, during which they performed a mental addition task or an articulation task. A control condition consisted of a no-interference task. Both age groups were divided according to individual educational level (greater or less than the median number of school years in each age group). The results revealed a significant effect of education. Moreover, the education effect interacted with the task - participants with less education were more impaired in mental addition than in articulation. However, neither the age effect nor the interactions involving age reached significance.

Floden, Stuss, and Craik (2000) studied whether normal aging was associated with faster forgetting in the Brown-Peterson task. They hypothesized that, in light of documented age differences on other tasks, older adults would show disproportionate forgetting on the Brown-Peterson task as retention interval lengthens. 25 younger (aged 20-29 years) and 25 older (aged 57-69 years) subjects participated in experiment 1. Memory items for each trial were three consonants drawn randomly from the alphabet. The letters were read aloud by the examiner at a rate of one letter per second. The cue for recall was a knock on the table. On the first 5 trials, recall was tested immediately. For the 15 remaining trials, the letters were followed by a 3-digit number and participants were instructed to count backwards from that number by threes until cued for recall. Trials involved randomly ordered delays of 9, 18, or 36 seconds; 5 trials were given at each of the delays. Experiment 1 did not indicate an age-related increase in rate of forgetting. However, this procedure allowed for differences in rehearsal opportunity, task difficulty, and amount of information to be processed. 24 younger and 24 older subjects participated in experiment 2, which controlled for these factors and revealed significant age differences in the forgetting function. The experiment confirmed the presence of an age-related deficit in overall recall in the Brown-Peterson task.

Inman and Parkinson (1983) compared the memory retention of 27 elderly adults (64-80