Details of Grant 

EPSRC Reference:	GR/H52245/01
Title:	USE OF SECOND-ORDER MOTION TO CLARIFY THE COMPUTATIONAL MOTION-DETECTION STRATEGIES USED IN HUMAN VISION
Principal Investigator:	Smith, Professor AT
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Department:	Sch of Psychology
Organisation:	Cardiff University
Scheme:	Standard Research (Pre-FEC)
Starts:	01 June 1993	Ends:	31 March 1994	Value (£):	107,899
EPSRC Research Topic Classifications:	Vision & Senses - ICT appl.
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Summary on Grant Application Form
(1) To establish more clearly the number of discrete motion-sensing mechanisms that exist in the human visual system.(2) To identify the computational strategy used by each such motion detection system (and in particular the long-range system).(3) Where possible, to associate the motion systems so identified with their underlying anatomical and physiological substrates.Progress:The question of whether second-order motion is detected by a lowlevel motion energy strategy or by a high-level feature-tracking strategy has been addressed in several experiments. Firstly, we have measured thresholds for detecting the orientation and direction of a drifting one-dimensional contrast modulation. The two thresholds are similar under most conditions, as they are for first-order motion, and thresholds decline with eccentricity at the same rate as for first-order motion. This work, which suggests the use of a low-level strategy, has been published (1). Investigations of perceived direction in more complex contrast modulations have provided more direct evidence f or a low level mechansim and, in addition, suggest that we can fall back on a feature-matching strategy when the low-level mechanism fails. This work too, is published (2). Experiments on the effect of contrast on perceived speed of second-order motion have been conducted and experiments on the effects of adaptation on perceived speed are in progress. 1) Smith, A.T., Hess, R.F. and Baker, C.L.Jr. Direction identification thresholds for second-order motion in central and peripheral vision Journal of the Optical Society of America A. 1994, 11, 506-514. 2) Smith, A.T. Correspondence-based and energy -based detection of second-order motion in human vision. Journal of the Optical Society of America A. 1994,11, 1940-1948.
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