Reproduction of Synthetic 2-d Actions: Learning and Limitations

Subjects observed and then reproduced abstract, irregular stimulus models generated by the steady movement of a disk across two-dimensional paths. Each path comprised 3 to 7 randomly-oriented linear segments linked head-to-foot. Reproductions were expressed by moving a stylus over the surface of a graphics tablet while the disk was tracing its trajectory (Concurrent reproduction), or half a second after the disk had finished (Delayed reproduction). For both Concurrent and Delayed conditions, fidelity of reproduction fell with increasing number of linear segments in the model. Overall quality of reproduction did not differ between the two conditions. When a few models were repeated, interspersed among non-repeated ones, performance improved, but only when reproduction was delayed. This improvement was stimulus-selective, not a general improvement with practice. Additional experiments showed that memory for a seen model is well preserved for at least six seconds, and that imprecision in visual encoding significantly limits the quality of reproduction.