Principal Investigator:Lawrence Marks, PhD
Director Emeritus and Fellow
The John B. Pierce Laboratory
Lawrence Marks, PhD, and his research group study the ways that sensory systems transduce and process patterns of stimulus energy, and how the resulting information is encoded and represented in perception and cognition. Although each sensory system is clearly specialized in the stimuli that it processes and in its neural mechanisms, there are nonetheless important principles and characteristics common to different modalities. By studying sensory information processing generically, the research group aims to elucidate the similarities and commonalities as well as the differences among the senses of touch, hearing, vision, taste, and smell.
Current research includes three core projects. The primary project investigates mechanisms underlying the perception of flavor. Flavor perception is first and foremost a multisensory phenomenon, in which signals from olfaction, taste, and somatosensation combine to create the gamut of flavors of foods and beverages. Research in this first project aims at understanding how sensory signals, especially signals from olfaction and taste, combine and interact in the flavor system. Equally important to these studies are the ways that the multisensory flavor signals interact with cognitive information that comes, for example, from verbal labels. These interactions depend on the extent to which both the cognitive information and sensory signals are statistically associated with the flavor stimuli. Our research on flavor perception capitalizes on a Pierce-designed and Pierce-built computerized delivery system that automatically controls the flow of liquid flavorants to the subject, allowing precise timing of both the stimuli presented and the subject’s responses.
A second project investigates multisensory interactions in other sensory systems, mainly vision and hearing. An example is the so-called ‘ventriloquist effect,’ where the perceived location of a sound shifts toward the location of a simultaneous visual event that is spatially displaced from the sound (as when a ventriloquist’s voice appears to come from the moving mouth of the ventriloquist’s dummy). Recently, we found that displacing the perceived location of a sound through ventriloquism can improve the detection of the sound in a noisy background. Results like these suggest that multisensory interactions can arise at relatively early stages of sensory processing.
The third project investigates perceptual and cognitive processes related to synesthesia. Synesthesia refers to unusual cross-sensory or cross-perceptual experiences reported by small portion of the population, who may, for example, perceive sounds or tastes to have shapes, or letters or numbers printed in black or white to have colors. Synesthesia likely depends on distinct, genetically based brain mechanisms, although the precise nature of these mechanisms is not yet clear. A main goal of this third project is to elucidate the sensory and cognitive processes that contribute to synesthesia. In particular, we have evidence that several of these processes also contribute to perception and cognition in people who do not experience synesthesia. Understanding synesthesia may thereby help to illuminate universal mechanisms of human behavior.
Marks, L.E. (1974). Sensory Processes: The New Psychophysics. New York : Academic Press.
Marks, L.E. (1978). The Unity of the Senses: Interrelations among the Modalities.New York: Academic Press.
Marks, L.E. (2004). Cross-modal interactions in speeded classification. In G. Calvert, C. Spence , and B.E. Stein (Eds.), The Handbook of Multisensory Processes.Cambridge , MA : MIT Press, pp. 85-106.
Marks, L.E. , & Odgaard, E.C. (2005). Developmental constraints on theories of synesthesia. In L.C. Robertson and N. Sagiv (Eds.), Synesthesia: Perspectives from Cognitive Neuroscience. New York : Oxford University Press, pp. 214-236.