Biased weighting of temporally discrete visual stimuli in a continuous report decision-making task: A combined behavioral and electrophysiological study.

Integrating evidence from multiple sources to guide decisions is something humans do on a daily basis. Existing research suggests that not all sources of information are weighted equally in decision-making tasks, and that observers are subject to biases in the face of internal and external noise. Here we describe two experiments that measured observers' ability to integrate successive visual signals. Participants viewed pairs of gratings presented sequentially and reproduced their average orientation. Experiment 1 revealed a recency bias in evidence integration, such that observers' average judgments were closer to the orientation of the second grating than the first. Mixture distribution modeling revealed that this was caused by a recency bias in averaging, as well as a tendency to disregard the first stimulus altogether in some trials. In Experiment 2 we replicated these findings, and quantified orientation-specific patterns of neural activity recorded during the task using population-tuning curve modeling of electroencephalography data. This analysis yielded robust orientation tuning to both the presented gratings and observers' decisions, and suggested that observers were storing both grating stimuli for subsequent averaging rather than computing a running average. The neural representation of the second grating was not reliably stronger than that of the first, suggesting that the recency bias is not due to a difference in the strength of encoding of the second stimulus, and instead may arise at a later decision stage where information is retrieved or integrated. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Synchronous and asynchronous perceptual bindings of colour and motion following identical stimulations.

When a moving surface alternates in colour and direction, perceptual couplings of colour and motion can differ from their physical correspondence. Periods of motion tend to be perceptually bound with physically delayed colours - a colour/motion perceptual asynchrony. This can be eliminated by motion transparency. Here we show that the colour/motion perceptual asynchrony is not invariably eliminated by motion transparency. Nor is it an inevitable consequence given a particular physical input. Instead, it can emerge when moving surfaces are perceived as alternating in direction, even if those surfaces seem transparent, and it is eliminated when surfaces are perceived as moving invariably. For a given observer either situation can result from exposure to a common input. Our findings suggest that neural events that promote the perception of motion reversals are causal of the colour/motion perceptual asynchrony. Moreover, they suggest that motion transparency and coherence can be signalled simultaneously by subpopulations of direction-selective neurons, with this conflict instantaneously resolved by a competitive winner-takes-all interaction, which can instantiate or eliminate colour/motion perceptual asynchrony.