Colour Detection on Bivariate Choropleth Maps: The Visual Search Process

Searching is a fundamental but complex task in the map-reading process. Several psychologists have explored the role of visual search in cognition, and have proposed a number of models that may offer cartographers a basis for understanding how people search for specific map information. The purpose of this research was to examine the visual search process used by map readers when interacting with bivariate choropleth maps, and to assess the potential of one of psychology's models, Attentional Engagement Theory, for explaining that process. The study employed a standard search task that determined the efficiency of the search process by having subjects search for target colours among non-target colours across a map. An analysis of reaction times showed that the following variables affected search efficiency: target colour, the total number of objects on the map, and similarity of the target colour to all other non-target colours on the map.