My research is concerned with visual information processing, that is, discovering what information is available to the visual system and what parts of that information are actually used. In my experiments, observers usually are trained to perform their best by giving them feedback and practice to help them learn a task. This best performance can be compared across tasks in order to assess what information is actually used to do a specific discrimination or detection.

My research is concerned with visual information processing, that is, discovering what information is available to the visual system and what parts of that information are actually used. These psychophysical experiments are carried out on adult humans. In my experiments, observers usually are trained to perform their best by giving them feedback and practice to help them learn a task. This best performance can be compared across tasks in order to assess what information is actually used to do a specific discrimination or detection.

I am especially interested in how we perceive the speed and direction of objects in motion. My approach to studying motion perception includes trying to discover the motion system's limitations and determining what those limitations can tell us about how the system works. I am also interested in how we determine the relative position of objects in dept and how differences in relative depth can influence what shapes observers see. These different kinds of information (among many others) are integrated by the visual system to form a unified perception of the world, since we do not perceive motion information as distinct from position information for the same object. Interactions between the different processes can tell us how the different types of information are combined.

The goal of my research is to discover the mechanisms the brain uses to solve perceptual problems. The visual system is a convenient system to work with because the input can be defined very precisely. There is also a large community, especially at Brown, working on the visual system including scientists in psychophysics, physiology, and computational modelling.

Brown University funded small grant ($900)

Matthews, N. and Welch, L. (1997) The effect of inducer polarity and contrast on the perception of illusory figures. Perception, 26, 1431-1443.

Welch, L., MacLeod, D.I.A. and McKee, S. P (1997) Motion interference: Perturbing perceived direction. Vision Research, 37(19), 2725-2736.

Festa, E.K. and Welch, L. (1997) Recruitment mechanisms in speed and fine-direction discrimination tasks. Vision Research, 37(22), 3129-3144.

McKee, S.P. and Welch, L. (1992) The precision of size constancy. Vision Research, 32, 1447-1460.

Welch, L. (1989). The perception of moving plaids reveals two motion-processing stages. Nature, 337, 734-736.

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Member of the Society of Sigma Xi
Member of the Association for Research in Vision and Ophthalmology
Member of the American Psychological Society
Member of Vision Sciences Society