James E. Hoffman

Department of Psychology
Phone: (302) 831-2453: Office

Office: Room 224L Wolf Hall: 831-1137: Lab (302) 831-3645: Fax

Research Interests

My research in the area of visual attention in the last two years has focused on the relation between visual attention and eye movements. In a paper that appeared in Perception and Psychophysics (Hoffman and Subramaniam, 1995), Subramaniam and I showed that saccades to a location in space are preceded by a shift of visual attention to that location. Previous experiments had come to conflicting issues on this point due to a variety of methodological problems. This literature was reviewed in a chapter (Hoffman, 1998) which presents a methodological critique of the literature on attention and eye movements and shows that these two processes are coupled in producing saccades, pursuit movements, and vergence movements. Further experiments on this topic are in progress.

In addition, Suzanne Mueller and I (Hoffman and Mueller, submitted) showed that visual attention is allocated in a 3-D space where depth is provided by binocular disparity. Previous research had failed to find effects of attending in stereo space because subjects were cued to attend to "empty locations." That is, a visual cue was presented pointing to an unoccupied location in the 3-D display. We found that the critical factor in producing the effect is to ask subjects to attend to an object or surface in space.

I am also using event-related brain potentials (ERPs) to explore visual attention. For her Master's thesis, Pam Mundis explored the distinction between object-based and space-based attention using ERPs. Steve Hillyard and colleagues have shown that attention to spatial locations is associated with enhancement of two "early" ERP components: the P1 (~80 msec) and the N1 (~150 msec). Pam Mundis showed that attending to one of two overlapping figures results in enhancements in the P1 component, similar to that found in studies of spatial attention. This finding suggests that spatial attention to an object's contours may be involved in object-based attention.
 
 

Spatial Deficits in Williams Syndrome

In a new project funded by grants from the March of Dimes, NSF and NIH, I am collaborating with Dr. Barbara Landau in a study of the nature of spatial deficits in children with Williams Syndrome and how these deficits impact on their use of spatial language. Williams syndrome is a rare, genetically-based disorder resulting in mild mental retardation and an unusual pattern of strengths and weaknesses in cognitive abilities. Relatively preserved language capacities are paired with profound impairments in spatial ability. Barbara Landau and I are using eye tracking measures obtained during the performance of various spatial construction tasks to gain a detailed understanding of the nature of their spatial deficit and how it affects spatial language

Recent Publications

• Hoffman, J. E. (in press). Stages of Processing in Visual Search and Attention. To appear in: Challis, B., & Velichovsky, B. (Eds.) Stratification in cognition and consciousness. Amsterdam/Philadelphia: John Benjamins.
• Hoffman, J.E. (1998), Visual attention and eye movements. In H. Pashler (Ed.), Attention. London: University College London Press, 119-154.
• St. George, M. Mannes, S., & Hoffman, J.E. (1997). Individual differences in inference generation: An ERP analysis. Journal of Cognitive Neuroscience, 9, 776-787.
• Hoffman, J. E., & Subramanium, B. (1995). The role of visual attention in saccadic eye movements. Perception and Psychophysics, 57, 787-795.
• St. George, M., Mannes, S., & Hoffman, J. E. (1994). Global semantic expectancy and language comprehension. Journal of Cognitive Neuroscience, 6, 70-83.
• Nigam, A., Hoffman, J. E., & Simons, R. F. (1992). N400 and semantic anomaly with pictures and words. Journal of Cognitive Neuroscience, 4, 15-22.

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