Data from: Decision-level adaptation in motion perception

Prolonged exposure to visual stimuli causes a bias in observers'
responses to subsequent stimuli. Such adaptation-induced biases are
usually explained in terms of changes in the relative activity of sensory
neurons in the visual system which respond selectively to the properties
of visual stimuli. However, the bias could also be due to a shift in the
observer's criterion for selecting one response rather than the
alternative; adaptation at the decision level of processing rather than
the sensory level. We investigated whether adaptation to implied motion is
best attributed to sensory-level or decision-level bias. Three experiments
sought to isolate decision factors by changing the nature of the
participants' task while keeping the sensory stimulus unchanged.
Results showed that adaptation-induced bias in reported stimulus direction
only occurred when the participants' task involved a directional
judgement, and disappeared when adaptation was measured using a
non-directional task (reporting where motion was present in the display,
regardless of its direction). We conclude that adaptation to implied
motion is due to decision-level bias, and that a propensity towards such
biases may be widespread in sensory decision-making.