Ph.D., Stanford University
B.A., Cornell University

Overview
Bruce Bridgeman studies spatial aspects of vision. His research has clarified the relationships between two distinct representations of visual space in the brain, one underlying visual perception and the other controlling visually guided behavior. In the laboratory, these two aspects of visual processing have been isolated, with different spatial values assigned to each representation. The behavioral system has been shown to be unconscious and to have no memory, but it codes position accurately even when the perceptual system codes position inaccurately.

Bridgeman has developed a simple "eyepress" method for separating the motor commands to the eye from the position of gaze in space. The method has been adapted to investigate the role of motor commands in visual function and the role of visual backgrounds in spatial orientation.

Another interest in Bridgeman's laboratory is spatial processing associated with eye movements. The group is investigating distortions of space perception between one visual fixation and the next, as well as the effects of attention on perception and visual search. Another interest in Bridgeman's laboratory is spatial processing associated with eye movements.

Current Projects

1. Motor and cognitive function isolated with visual illusions. We are investigating various cognitive illusions to find cases in which motor and cognitive measures yield different spatial locations. These will help us to tease apart the functions of cognitive and motor representations of visual space respectively. (C. Sampanes)


2. Interaction of cognitive and motor space. A subject performs imaginary rotations in a memorized conceptual space, while standing and rotating in place. Under these conditions, imagined rotations are more likely to be ignored if they are in the direction opposite the real rotation, indicating a link between the processing of conceptual space (which has been described only verbally) and the control of actual motor activity. We are now tracking down the visual, proprioceptive, vestibular and efference cues that contribute to this interaction. (S. Macramalla)


3. Inattentional blindness is the failure to perceive an event that would otherwise be clearly visible, if attention is diverted elsewhere. We have found that even a stimulus that is not perceived can influence the apparent location of an object that is perceived. (B. Lathrop)


4. Visual search is explained by several models. We propose to differentiate them in search tasks with groups of distractors of varying sizes, densities and eccentricities. (P. Thiem)


5. Modeling of visual masking, especially metacontrast, continues with computer simulations. (B. Bridgeman)


6. In collaboration with Massimo Turatto in Italy, change blindness is being used as a tool to uncover mechanisms of visual perception and especially integration of information across saccadic eye movements. (B. Bridgeman)

Research Team - Graduate Students
3rd year: Steven Macramalla
4th year: Chad Sampanes
Passed qualifying exam: Paul Thiem
Recent PhD: Brian Lathrop, June 2003
Undergraduate Research Assistants
a rotating group of about 10 students

Lab Tour
The laboratory space of the Vision Research Laboratory consists of a reception area and workshop, 409 Social Sciences 2, three adjoining rooms used for experimental setups, and a larger room for computer work. Each experimental room is painted black for light isolation and has light-tight doors, separate ventilation, and separate electrical circuits. One of the rooms is electrically isolated and shielded.

Research Facilities
Existing equipment consists of a Bouis infrared eye tracker, an ASL head-mounted eye tracker, a 6 degree-of-freedom Polhemus position tracker that is currently head-mounted, a motorized oscillating chair, and numerous computers (mostly Macs), some with analog/digital interfaces. Experiments are controlled through the Psyscope program, which has a graphic interface for designing trials and trial sequences. There are also assorted oscilloscipes, power supplies, building materials, power tools, etc.

Physiological mechanisms of visual perception and cognition, computer simulation of cognitive processes, space perception, eye movements.

2006 - Bridgeman, B. Contributions of lateral inhibition to object substitution masking and attention. Vision Research, 46, 4075-4082. http://dx.doi.org/10.1016/j.visres.2006.08.012

2005 - Bridgeman, B. Influence of visually-induced expectation on perceived motor effort: A visual-proprioceptive interaction at the Santa Cruz Mystery Spot. Psychonomic Bulletin and Review, 12, 549-552.

Turatto, M. and Bridgeman, B. Change perception using visual transients: object substitution and deletion. Experimental Brain Research, 2005, published online: 26 July 2005.

Di Lollo V., von Muhlenen A., Enns J.T., and Bridgeman B. Decoupling stimulus duration from brightness in metacontrast masking: Data and models. Journal of Experimental Psychology: Human Perception & Performance, 2004, 30, 733-745.

Dassonville, P., Bridgeman, B., Bala, J.K., Thiem, P. and Sampanes, A. The induced Roelofs effect: two visual systems or the shift of a single reference frame? Vision Research, 2004, 44, 603-611.

Turatto, M., Galfano, G., Bridgeman, B. and Umilta’, C. Space-independent modality-driven attentional capture in auditory, tactile and visual systems. Experimental Brain Research, 2004,155, 301-310.

Psychology and Evolution: The Origins of Mind. Thousand Oaks, Ca.: Sage Publications, 2003.

Turatto, M., Bettella, S., Umilta’, C. and Bridgeman, B. Perceptual conditions necessary to induce change blindness. Visual Cognition, 2003, 10, 233-255.

Anand, S. and Bridgeman, B. An unbiased measure of the contributions of chroma and luminance to saccadic suppression of displacement. Experimental Brain Research, 2002, 142, 335-341.

The grand illusion and petit illusions - Interactions of perception and sensory coding. Journal of Consciousness Studies, 2002, 9, 29-34.

A comparison of two lateral inhibitory models of metacontrast. Journal of Mathematical Psychology, 2001, 45, 780-788.

Bridgeman, B., Gemmer, A., Forsman, T., and Huemer, V. Properties of the sensorimotor branch of the visual system, Vision Research, 2000, 40, 3539-3552

Durations of stimuli displayed on video display terminal: n-1/f + persistence, Psychological Science, 1998, 9, 232-233.