Feature binding of a continuously changing object.

Consider a feature of a stimulus (such as color, luminance, or spatial frequency) that changes over time along a continuum. When a second stimulus is briefly pulsed with the same feature value as the first stimulus, the two stimuli are not perceived to match. Instead, the continuously changing stimulus is perceived to be further ahead on the feature continuum than the pulsed stimulus [Nat. Neurosci. 3, 489 (2000)]. This shift is quantified by the amount of time ahead on the changing continuum, which is different for various types of features. A basic question is how our percepts are affected when an object has two continuously changing features (such as color and orientation) with different magnitudes of time ahead. This was addressed using a bar continuously changing in both color and orientation. Even though the two features were part of the same object, each feature maintained a distinctly different time ahead. This implies that observers perceived at each moment a combination of color and orientation that never was presented to the eye.