Locational representation in imagery: a moving spot task

Subjects with eyes closed imagined a spot moving from cell to cell in a matrix in response to spoken instructions: Up, Down, Left, and Right. After 12 such moves from a given starting point, the subject indicated the final position of the spot. Accuracy was studied as a function of matrix order, which varied from 3 X 3 to 8 X 8. (Visual angles of the displayed matrices were also varied, from 4.6 degrees/cell in one experiment to 1 degree/cell in another, but with little or no effect on results.) The greatest decrement in accuracy occurred between 3 X 3 and 4 X 4 cells. Moreover, showing the subjects a systematic way of structuring matrices (i.e., of dividing them into parts that could be visualized more or less individually) improved performance markedly on all but the 3 X 3 matrix. These results, which agree fairly well with the verbal reports of the subjects, indicate that some capacity limitation of the image system is exceeded in going from a 3 X 3 to a 4 X 4 grid. Implications concerning the nature of imagery are discussed.