Sensory Sensitivities and Discriminations and Their Roles in Aviation

Evidence that intersubject differences in the ability to process motion-defined (MD) shape are not predicted by the ability to process luminance- defined (LD) shape, that motion is processed by hierarchical manner, that discrimination and detection can be dissociated for MD form, and that spatial discrimination for MD and LD form are not entirely mediated by the same mechanism is as follows. (A) Reducing presentation duration or dot lifetime from 1.0 to 0.1 sec progressively reduced the visibility of a MD bar, but did not reduce orientation discrimination for the bar when visibility was held constant. (B) Detection and/or recognition of MD letters can be degraded by removal of brain tissue underlying prestriate cortex without affecting contrast sensitivity, Snellen acuity, low contrast acuity or sensitivity to motion. (2) Shape discrimination for an MD rectangle can be as low as 2-3%-as good as for an LD rectangle. (3) Evidence is reported for a neural mechanism sensitive to shape independently of size. (4) Evidence is reported for a neural mechanism directly sensitive to time to collision with an approaching object. A method is reported for measuring intersubject differences in discrimination of time to contact. (4) A titration method for uncovering the color-defined form system. (5) The 40 Hz human brain response indexes magnocellular activity. (6) By recording the magnetic field of the brain, an audio-visual integration area in the brain has been identified. Responses to texture-defined form and color-defined form have been unconfounded from responses to luminance-defined form. (7) A technique for measuring intersubject differences in susceptibility to glare has been developed and is being used in a prospective study of flying safety. Also, the test quantifies visual status in cataract patients.