Abstract

A detection task was performed using different pictographic representations of objects in order to test the hypothesis that high-level information (familiarity) may influence detection thresholds. The stimuli were five versions of forms: outline drawings of objects, silhouettes, and three fragmented versions of forms derived from the outlines. The stimuli varied on two parameters: their nameability (easily nameable, hardly nameable, and not nameable) as assessed by a naming task, and their energy content as assessed by a two-dimensional fast-Fourier transform. The greatest amount of energy was observed for silhouettes, and the amount of energy contained in the vertical and horizontal spatial frequency components was equivalent for outlines and the three versions of fragmented forms. Luminance thresholds for the detection of the forms were measured by means of an adaptive method. The results show that thresholds were determined only by the energy content of the stimuli. High-level semantic or name information had no influence on the detectability of the visual signal. The results are discussed in terms of the visibility of spatial frequency components at detection threshold.