TY - JOUR
T1 - A two-stage process model of sensory discrimination
T2 - An alternative to drift-diffusion
AU - Sun, Peng
AU - Landy, Michael S.
PY - 2016/11/2
Y1 - 2016/11/2
N2 - Discrimination of the direction of motion of a noisy stimulus is an example of sensory discrimination under uncertainty. For stimuli that are extended in time, reaction time is quicker for larger signal values (e.g., discrimination of opposite directions of motion compared with neighboring orientations) and larger signal strength (e.g., stimuli with higher contrast or motion coherence, that is, lower noise). The standard model of neural responses (e.g., in lateral intraparietal cortex) and reaction time for discrimination is drift-diffusion. This model makes two clear predictions. (1) The effects of signal strength and value on reaction time should interact multiplicatively because the diffusion process depends on the signal-to-noise ratio. (2) If the diffusion process is interrupted, as in a cued-response task, the time to decision after the cue should be independent of the strength of accumulated sensory evidence. In two experiments with human participants, we show that neither prediction holds. A simple alternative model is developed that is consistent with the results. In this estimate-then-decide model, evidence is accumulated until estimation precision reaches a threshold value. Then, a decision is made with duration that depends on the signal-to-noise ratio achieved by the first stage.
AB - Discrimination of the direction of motion of a noisy stimulus is an example of sensory discrimination under uncertainty. For stimuli that are extended in time, reaction time is quicker for larger signal values (e.g., discrimination of opposite directions of motion compared with neighboring orientations) and larger signal strength (e.g., stimuli with higher contrast or motion coherence, that is, lower noise). The standard model of neural responses (e.g., in lateral intraparietal cortex) and reaction time for discrimination is drift-diffusion. This model makes two clear predictions. (1) The effects of signal strength and value on reaction time should interact multiplicatively because the diffusion process depends on the signal-to-noise ratio. (2) If the diffusion process is interrupted, as in a cued-response task, the time to decision after the cue should be independent of the strength of accumulated sensory evidence. In two experiments with human participants, we show that neither prediction holds. A simple alternative model is developed that is consistent with the results. In this estimate-then-decide model, evidence is accumulated until estimation precision reaches a threshold value. Then, a decision is made with duration that depends on the signal-to-noise ratio achieved by the first stage.
KW - Discrimination
KW - Drift-diffusion
KW - Motion
KW - Orientation
KW - Psychophysics
KW - Reaction time
UR - http://www.scopus.com/inward/record.url?scp=84994460673&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84994460673&partnerID=8YFLogxK
U2 - 10.1523/JNEUROSCI.1367-16.2016
DO - 10.1523/JNEUROSCI.1367-16.2016
M3 - Article
C2 - 27807167
AN - SCOPUS:84994460673
VL - 36
SP - 11259
EP - 11274
JO - Journal of Neuroscience
JF - Journal of Neuroscience
SN - 0270-6474
IS - 44
ER -