| Abstract: | Two experiments are reported which investigate the organization of visuospatial information in post-iconic storage. In both experiments, stimuli consisting of 10 disks randomly placed in a four-by-five array were tachistoscopically presented to subjects whose task was to recreate the pattern. In Experiment 2, reproduction was constrained (on a row-by-row basis) while in Experiment 1 it was unconstrained. The results of Experiment 1 showed that subjects recalled in terms of “chunks” of spatially adjacent disks, with most “chunks” consisting of about three of four disks. Within each sequence of 10 responses the probability of correctly recalling a chunk decreased with its serial position but was relatively independent of chunk size per se (for chunks containing seven or less disks). In addition, clear topographical variations in accuracy were found, which tended to covary strongly with order of recall. In Experiment 2, the order of reproduction was prespecified (either top row down to bottom row, or bottom row up to top row) in order to induce chunking by rows. The direction of reproduction was either pre- or post-cued. The results of this study showed that subjects encode the stimulus, wherever possible, in a form which is compatible with the constraints imposed on recall order. The results for the postcued conditions provide strong support for the argument that topographical variations in accuracy are a function of variations in accuracy of encoding, and not simply a function of order of report. The results are discussed in terms of an attentional model. It is proposed that a general “anticipatory schema” (cf. Neisser, Cognition and Reality 1976) presets the distribution of attention in the visual field, preselects a set of coding heuristics, and subsequently interacts with the present stimulus pattern. Spatial discontinuities in the distribution of attention resulting from this interaction are regarded as “defining” chunks of stimulus elements. |
