Two routes of visual information: differences between sensory-perceptual and sensorimotor processes in humans

• Applicant: Professor Dr. Florian Waszak
• Subject Area: Personality Psychology, Clinical and Medical Psychology, Methodology
• Term: from 2003 to 2007
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5421500

The project will investigate the relationship between sensory-perceptual and sensorimotor processes in humans. We will address the question as to whether the trigger of a motor response depends on the internal response exceeding a (perceptual) criterion or some unrelated threshold proper to the motor system. A further objective of the project is to provide a new paradigm that allows for the quantification of the impact of near-threshold stimuli on the motor system. We will use a metacontrast paradigm: two visual stimuli are presented in rapid succession with the first (masked) stimulus presented within the bright, highly visible annulus of the second (backward masking) stimulus. The masking stimulus hampers the perception of the masked stimulus. We measure both the observers` perceptual and motor behaviour elicited by the same stimulus on a "trial-by-trial" basis. On any given trial the reaction time (RT) to the occurrence of any of the two (masked and masking) stimuli is recorded together with the oberservers` response on the presence/absence of the masked stimulus. RTs are analysed as a function of both the presence/absence of the masked stimulus and the observers internal state (stimulus reported or not). Preliminary data schow that masked stimuli affect RTs only if they have been consciously perceived, i.e., if their internal responses exceed the perceptual criterion. This result contradicts other experiments reported in the literature. One part of the proposed project tries to resolve this contradiction. We suppose that the relationship between sensory-perceptual and sensorimotor processes depends on the compatibility of stimulus information and motor response. For example, the same external event (a luminance increment in the periphery) may have a stronger effect on the motor system, if the motor response consists in a saccade instead of a finger flexion (i.e., a key press).

• DFG Programme: Research Grants