Effects of repeated trials on the strategy used for a hand laterality judgment task

The hand laterality judgment task requires participants to determine whether a picture of a hand picture, presented at various rotational angles, depicts a left or right hand. Task performance is generally thought to rely on motor imagery (MI) for palm-view pictures and visual imagery (VI) for back-view pictures. However, the influence of repeated task execution on performance strategies remains unclear. This study examined the relationship between self-reported strategies and response time (RT) profiles during a 512-trial hand laterality judgment task in 42 healthy adults. Based on post-task self-reports for palm-view pictures, participants were classified into the MI group, who reported consistently using MI throughout the trials, and the MI–VI group, who reported switching from an MI to VI. In the MI group, RT profiles consistently showed longer RTs for lateral palm-view pictures (outward-pointing fingers) than for medial orientations (inward-pointing fingers), characteristic of MI use, across both halves of the task. The MI–VI group showed similar RT patterns initially, but in the second half, RT differences between lateral and medial orientations diminished, suggesting a shift toward VI-like characteristics. These findings suggest that although both groups may have used MI, RT trends varied according to the participants’ self-reported strategies. In the MI group, both explicit self-report and implicit RT profiles indicated sustained MI use, whereas the MI–VI group, self-reports indicated a strategy shift to VI, and their RT profiles suggest a combined use of MI and VI.