Visit the Carrasco LabPerception and Attention
I received my doctorate from Princeton University in 1989 My dissertation dealt with the relationship between spatial resolution and temporal sensitivity properties of the human visual system. Before coming to NYU, I was an assistant professor at Wesleyan University, CT. My research aims to understand the relationship between the psychological and physiological mechanisms involved in the basic processes of visual perception andattention. The theoretical framework for my research draws from work in perception, cognitive psychology, and neurophysiology. Themethodology is based on visual psychophysics. My current research has two goals: First, to develop a model of visual search that takes into account known sensory factors, such as spatial resolution and lateral inhibition, and attentional mechanisms thought to facilitate the processing of relevant information by enhancing its perceptual representation and/or improving decisional mechanisms. Second, to characterize the attentional mechanisms that affect early visual processing.
Visual Search: Perception and Attention
My students and I have demonstrated that visual search theories should take into account fundamental visual mechanisms such as spatial resolution and lateral inhibition (Carrasco, Evert, Chang & Katz, 95; Carrasco & Frieder, 97). We characterized a pronounced and persistent eccentricity effect: targets appearing at peripheral locations are detected (Carrasco et al., 95), localized and identified (Carrasco & Theofanou, 97) more slowly and less accurately than those appearing near the central fixation point. Analyzing performance as a function of target eccentricity revealed a dramatic confound: the set size effect increased with target eccentricity (Carrasco et al., 95, 98; Carrasco & Frieder, 97; Carrasco & Yeshurun, 98). This confound challenges the commonly accepted theoretical interpretations of set size effects, so that they can no longer be considered a direct measure of covert attentional processes. To assess accurately the set size effect, we controlled for retinal inhomogeneity via a cortical magnification factor. We showed that variation in spatial resolution accounts for the eccentricity effect as well as for a large portion of the set size effect in search performance (Carrasco & Frieder, 97). Furthermore, we documented how visual search performance, in general, and the eccentricity effect, in particular, are also affected by the spatial properties of the stimuli, such as stimulus size, spatial frequency and orientation (Carrasco et al., 98).
Visual attention and perceptual organization
We re-assessed the role of covert attention in visual search by peripherally cueing the target location. When attention was directed to the target location, the set size and the eccentricity effects were attenuated but not eliminated, even though observers could devote all their attentional resources to the relevant location. These findings provide convergent evidence indicating that the set size effect does not necessarily result from the serial deployment of attention (Carrasco & Yeshurun, 98). We suggested that covert attention may indeed enhance the perceptual representation of the stimulus, and that this enhancement diminishes the eccentricity effect, which in turn reduces the set size effect. This hypothesis has received further support from three recent studies.
Visual attention and contrast sensitivity
We first reported the benefits of spatial covert attention on contrast sensitivity for detection and discrimination tasks in a wide range of spatial frequencies. When observers were presented with vertical and horizontal Gabor patches a detection model of external noise reduction accounted for the cueing benefit in a discrimination task. However, such a model could not account for this benefit when location uncertainty was reduced, either by: (a) Increasing overall performance level; (b) increasing stimulus contrast to enable fine discriminations of slightly tilted supra-threshold stimuli; and (c) presenting a local post-mask. Given that attentional benefits occurred under conditions that exclude all variables predicted by the external noise reduction model, these results support the signal enhancement model of attention (Carrasco, Penpeci-Talgar & Eckstein, 2000).
Chair, Psychology Department, New York University (2001 - present)
Selected Fellowships & Awards
Guggenheim Fellow (1999-2000).
Liu, T., Pestilli, F., & Carrasco, M. (2005) Transient attention enhances perceptual performance and fMRI response in human visual cortex. Neuron. 45, 469-477.
Gobell, J. & Carrasco, M. (2005) Attention alters the appearance of spatial frequency and gap size. Psychological Science, 16, 644-651.
Pestilli, F., & Carrasco, M. (2005) Attention enhances contrast sensitivity at cued and impairs it at uncued locations. Vision Research, 45, 1867-1875.
Carrasco, M., Ling, S. & Read, S. (2004) Attention alters appearance. Nature Neuroscience, 7, 308-313.
Carrasco, M., McElree, B., Denisova, K.& Giordano, A.M. (2003). Speed of Visual Processing Increases with Eccentricity, Nature Neuroscience, 6(7): 669-670 [pdf]
Carrasco, M., Williams, P. E., & Yeshurun, Y. (2002). Covert attention increases spatial resolution with or without masks: Support for signal enhancement. Journal of Vision, 2(6), 467-479, [pdf], DOI 10.1167/2.6.4.
Carrasco M, Penpeci-Talgar C & Cameron EL (2001) Characterizing visual performance fields: Effects of transient covert attention, spatial frequency, eccentricity, task and set size. Spatial Vision 15: 61-75 [pdf]
Carrasco, M. & McElree, B. (2001). Covert attention accelerates the rate of visual information processing. Proceedings of the National Academy of Sciences. 98: 5363-5367.[pdf]
Yeshurun, Y. & Carrasco, M. (2000) The locus of attentional effects in texture segmentation. Nature Neuroscience, 3 (6) 622-627. [pdf]
Carrasco, M., Penpeci-Talgar, C. & Eckstein, M. (2000). Spatial attention increases contrast sensitivity across the CSF: Support for signal enhancement. Vision Research, 40(10-12). [pdf]