The effect of repetition on the perception of single letters)

Single letters were presented for from one to five flashes, with S required to report what he saw after each f1ash. The clarity of the letter increased sharply with repetition. Since the letters were no larger than one-third of a degree in size, clarity could not have .been increased by S making different fixations from f1ash to f1ash and combining them into a total percept. Nor was S guessing, since this could be ruled out by other indicators. Thus, it was concluded that repetition of the stimulus can have a direct effect on the clarity of a S’s percept of that stimulus.     

The Shellen chart as a test of visual acuity

Summary An analysis of the mistakes made by 100 boys in reading the letters on a Snellen Chart reveals great differences in legibility between letters of the same size. This is found to depend on the shape and familiarity of the letter and its similarity to other letters. Whether a test of visual acuity consists of two-point discrimination or the perception of meaningful shapes, mental organization is a deciding factor in determining the response. While oculists are interested in the part played by the eye in vision, psychologists direct attention to the part played by the mind.Based on a paper read at the British Association Meeting at Newcastle in September, 1949.