Effects of Mental Shift and Stimulus Discrimination on Planning

Abstract

The present study examined effects of perceptual features of the Tower of London (TOL) Test on planning performance by means of manipulating visual properties of the beads used to make planned movements. The same planning problems were used in three different versions of the TOL. That is, they were solved by exactly the same successive moves but each version had different target configurations that consisted of two dimensional (color and shape) or one dimensional (color) beads. In the two-dimensional TOL (2D-TOL test), the planning problems were solved according to either color or shape dimensions of four beads, whereas in the Tower of Conflict Test (TOC), participants were required to discriminate their four beads as two beads to be matched in shape and two in color to a problem configuration. The results revealed that performance on the TOL with one-dimensional beads significantly differed from those on the TOC and the 2D-TOL indicating that planning and execution of movements were influenced by mental shifts between two dimensions (color and shape) of the beads and stimulus discrimination processes. In addition, same problem was solved 4 times in succession by a control group, who did not shift between the two dimensions, and by a mental shift group, who were required to shift to the other dimension after solving a problem two times in succession, and trend analyses were used to examine changes due to mental shift. Polynomial contrasts revealed only a significant linear trend for the control group, while quadratic and cubic trends were observed across the repeated measures of same planning problem for the mental shift group.