1 research outputs found
Visual detection of time-varying signals: opposing biases and their timescales
Human visual perception is a complex, dynamic and fluctuating process. In
addition to the incoming visual stimulus, it is affected by many other factors
including temporal context, both external and internal to the observer. In this
study we investigate the dynamic properties of psychophysical responses to a
continuous stream of visual near-threshold detection tasks. We manipulate the
incoming signals to have temporal structures with various characteristic
timescales. Responses of human observers to these signals are analyzed using
tools that highlight their dynamical features as well.
We find that two opposing biases shape perception, and operate over distinct
timescales. Positive recency appears over short times, e.g. consecutive trials.
Adaptation, entailing an increased probability of changed response, reflects
trends over longer times. Analysis of psychometric curves conditioned on
various temporal events reveals that the balance between the two biases can
shift depending on their interplay with the temporal properties of the input
signal. A simple mathematical model reproduces the experimental data in all
stimulus regimes. Taken together, our results support the view that visual
response fluctuations reflect complex internal dynamics, possibly related to
higher cognitive processes.Comment: Number of pages: 31 Number of figures: 2