Timecourse of a perceptual judgment and factors affecting it

Perceptual decisions are extremely fast and take on the order of milliseconds. The time taken to view the stimuli during these choices, termed processing time (PT), is an important quantity because it defines how informed, and thereby accurate, the choice is. Typically, the PT has been estimated from the reaction time (RT), which is the total amount of time taken to report a choice, starting from stimulus onset. The issue here is that the RT reflects not only the PT, but also related motor and other non-decision delays involved in a choice. To resolve this, the compelled-saccade (CS) task was developed. The CS task is a two-alternative forced-choice task with a crucial difference: the instruction to initiate a saccade (GO signal) precedes cue presentation, which is provided a variable delay later. This design achieves a separation between the perceptual and non-perceptual processes that constitute a choice, which then provides a means to extract PTs and study the speed of perceptual processing. To aid in this effort, the tachometric curve - a psychophysical metric that plots accuracy as a function of PT - was generated. Three features of the tachometric curve, namely, center-point, slope and maximum height help quantify the onset, speed and efficiency of perceptual processing, respectively.

Grantor dc:publisher

Wake Forest University

Year dc:date.issued

2012

Author dc:creator

• Shankar, Swetha

• Compelled-saccade

Language dc:language.iso

en

Handle dc:identifier.uri

http://hdl.handle.net/10339/37428

OAI identifier oai:identifier

oai:wakespace.lib.wfu.edu:10339/37428