Guessing instructions, experience with stimuli, and array structure in tachistoscopic letter identification

The roles of guessing instructions, familiarity with the stimuli, and array structure were assessed in a letter identification task. Seven retinal locations were sampled within the central 2.6 degrees of the visual field using an indicator that appeared either simultaneously with the array or immediately after it. Retinal locus was the major determiner of letter-recognition accuracy, producing W-shaped functions regardless of instructions, or degree of familiarity with the stimuli. Stimulus structure did not produce a systematic effect.