Abstract
Seeing with two eyes usually helps one respond faster. Here we show that with ambiguous stimuli, binocular viewing can paradoxically slow down reaction time. This is explained by the observers basing their decision on a noisy neuronal representation within the visual system, with the added noise breaking the symmetry between the two possible interpretations. Binocular integration improves the representation by reducing the noise, increasing ambiguity, and decision time. The neuronal Accumulator (Race) model is applied to quantify the underlying binocular integration. The model accounts for the distributions of reaction times, and predicts suboptimal integration between eyes. We conclude that under ambiguous stimulation neuronal noise within the visual system determines responses.
Highlights
Seeing with two eyes usually helps one respond faster
We show that with ambiguous stimuli, binocular viewing can paradoxically slow down reaction time
This is explained by the observers basing their decision on a noisy neuronal representation within the visual system, with the added noise breaking the symmetry between the two possible interpretations
Summary
Oren Yehezkel1,*, Anna Sterkin1,*, Dov Sagi2 & Uri Polat[1] received: 17 February 2015 accepted: 14 September 2015 Published: 18 November 2015. We show that with ambiguous stimuli, binocular viewing can paradoxically slow down reaction time This is explained by the observers basing their decision on a noisy neuronal representation within the visual system, with the added noise breaking the symmetry between the two possible interpretations. Among ambiguous grouping trials, the binocular responses were unexpectedly slower by 89.4 ± 17.6 milliseconds (Mean ± SE, N = 21) compared to the average of the monocular trials (p = 5.6 × 10−5); 2/3 of the subjects had slower binocular responses, but no one had faster binocular RTs. One possible explanation is that observers base their decision on a noisy neuronal representation of the stimulus, with the noise level serving as a “signal”. We suggest that in ambiguous grouping conditions, the evidence accumulated is determined by neuronal noise added to the otherwise equal stimulus-evoked responses This noise is reduced by binocular integration, making the neuronal responses supporting the two decision outcomes more similar. This proposal, combined with the Race model of human decision, explains the paradoxical slow-down of reaction times for decisions based on binocular viewing relative to monocular viewing
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