More than meets the eye: implicit perception in legally blind individuals

Legally blind participants (uncorrected vision of 20/200+) were able to identify a visual stimulus attribute (clock hand position) in the absence of consciously identifying its presence. Specifically, participants--with their corrective lenses removed--correctly guessed the hour-hand position above chance (8%) on a clockface shown on a computer screen. This occurred both when presented in a 1-clockface display (28%), as well as when shown a display containing 4 clockfaces (21%), in which only 1 face contained a hand. Even more striking, hand identification accuracy in the 4-clockface condition was comparable whether the clockface containing the hand was (21%) or was not (20%) correctly identified. That legally blind individuals are capable of identifying stimulus attributes without conscious awareness provides an additional vehicle for exploring implicit perception. Consistent with previous research, the visual system can apparently cope with degraded visual input through information available through a(n unconscious) secondary pathway via the superior colliculi.