Symmetry, development, and tachistoscopic recognition

First-, third-, and sixth-grade children and college adults were presented random-shapes for tachistoscopic recognition on four successive days. The sets of stimuli differed in amount of variability (5, 10, or 20 turns) and form (symmetrical and asymmetrical). The results supported the following generalizations. Recognition accuracy at tachistoscopic durations was facilitated by age of S, experience with the task, and reduction in the variability of the stimulus. Reduction of stimulus variability was achieved both by decreasing the number of coordinates used in generating the random shape (e.g., 5 vs. 20) or by the addition of bilateral symmetry to otherwise randomly generated shapes. The addition of symmetry to random shapes facilitates the recognition of 5- and 10-turn shapes, but interferes with the recognition of 20-turn shapes. This finding suggests that the addition of symmetry to shapes at or near the S's processing limit facilitates their recognition. However, in the case of shapes of high variability (20 turns), the addition of symmetry introduces perceptual noise, which disrupts the sampling strategy required for the recognition of high-variability shapes.