Compressed file length predicts search time and errors on visual displays

Search times and errors were recorded for targets (a gray triangle or trapezoid) in static marine radar, chart, and radar-chart overlay bitmap computer displays, and for targets in bitmap aerial photo displays. Lossless JPEG and ZIP compressed file lengths were obtained for each display. The two types of compressed file length were correlated and they predicted both the time to search each display and the number of search errors. Search time began increasing with increasing file size before errors began to increase. Compressed file size, an objective, easily obtained measure of display complexity, predicts both subjective complexity judgments (previous research) and objective search performance (these experiments). It is analogous to algorithmic complexity, a theoretical but impractical measure of bit string complexity. The data suggest that it may be possible to use the compressed file size measure to predict display performance in applied tasks.