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Title: Combining speed information across space
Author: Goodwin, Allen.
ISNI:       0000 0001 3505 1623
Awarding Body: University of Keele
Current Institution: Keele University
Date of Award: 2005
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In this thesis, we investigate the integration of local motion signals across space. We examined how both perceived speed and speed discrimination is affected by an increase in the number of local motion elements, their spatial separation, and their contrast. We found that the rate of integration was affected by contrast and the number of elements; the lower the contrast the greater the rate of integration. At a contrast close to threshold (7%) the rate of integration could be accounted for by probability summation of local speed signals across space. The effect of distance between speed cues was negligible. The improved speed discrimination sensitivity with an increase in element number could not be accounted for by increased detectability; for equally detectable stimuli, speed discrimination thresholds are decreasing with element number. Whereas element number strongly increases speed discrimination sensitivity, the effect on perceived speed is small and not always consistent across observers. Finally, the integrative process was found to be related to the direction of the local speed cue at high contrast (20%) whereas at low contrast (7%) the integrative process is direction blind. The implications of the results obtained within the context of this research are discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available