Recognition and detection of texture-defined letters.

We quantified texture segregation by measuring psychophysically the percent correct detection scores for a set of 10 texture-defined (TD) letters using two-alternative forced-choice, and at the same time quantified spatial discrimination of TD form by measuring psychophysically the percent correct letter recognition scores for the 10 letters using 10-alternative forced-choice. Ten levels of task difficulty were created by adding noise dots to the texture patterns. Two kinds of letters were used. Static textures had the same letter and the same texture pattern throughout any given 1-sec presentation. Dynamic textures had the same letter, but a different texture pattern for every one of the 70 frames during any given 1-sec presentation. For both static and dynamic textures, letter recognition scores fell to chance level from a lower number of noise dots than did letter detection scores. Both recognition and detection scores were generally better for dynamic than for static texture patterns. We suggest that, for dynamic textures, subjects were able to enhance the signal-to-noise ratios of the noisy letters by signal averaging.