The mediating effect of learning on the interference between location and distance recall from motor short-term memory

Abstract

Two experiments were conducted within a motor short-term memory paradigm to examine the influence of shifts in starting position upon the reproduction of movement location (experiment 1) and distance (experiment 2). We assessed whether the systematic pattern of undershooting and overshooting which occurs as a function of starting position changes is a consequence of learning which proceeds throughout the course of an experiment or is rather a more fundamental property of the encoding and retrieval processing occurring within motor short-term memory. Five groups of 10 subjects were each given 20 trials within a typical motor short-term memory paradigm. Each trial involved a criterion and reproduction linear-positioning movement separated by a 10-sec retention interval. The starting position for the reproduction movement was shifted by 0, 2 or 4 cm in either direction from the starting position of the criterion movement. The presentation order of the five shifts in starting position was counterbalanced among the five groups, and each group consecutively performed 4 trials per shift. Analysis of data obtained from only the starting position condition performed first by each of the subjects showed the same systematic pattern of undershooting and overshooting in movement reproduction as observed from the typical analysis based on the data obtained from all the starting position conditions. These results suggest that the systematic undershooting-overshooting pattern typically observed in motor short-term memory experiments is not a consequence of any learning which takes place during the course of the experiment and is hence not an artifact of any central tendency effects arising from exposure to a range of different movement distances and locations. Rather location-distance interference appears to result from more fundamental aspects of the encoding and retrieval of information from motor short-term memory.