TEXTURE DENSITY ADAPTATION AND THE PERCEIVED NUMEROSITY AND DISTRIBUTION OF TEXTURE

Three experiments were conducted to assess the impact of adaptation to dense visual texture on the perceived numerosity and spatial distribution of texture. Study participants compared fields of dots presented in 2 locations, 1 of which was adapted to dense arrays of dots. The effect of adaptation was assessed by measuring points of subjective equality between the adapted and unadapted regions for the perceived density, numerosity, and distribution (cluster) of texture with staircase procedures for textures containing 20-320 dots. Perceived texture density was reduced at all numerosities. For high numerosities, density adaptation markedly diminished the perceived numerosity but not the apparent cluster of the dots. At low numerosities, the opposite pattern of results emerged, suggesting that density is more influential in the perception of high numerosities and that perceptual distortions of number and cluster may be traded off with one another. A simulation study of Allik and Tuulmets's (1991) occupancy model of perceived numerosity is also presented, and suggestions are made for modifying the model based on the patterns of results found.