Category effects on estimates of stimuli: Perception or reconstruction?

The present study examined a common category effect that has been reported in the literature: the tendency for estimates of individual stimuli to be biased toward the central value of the presented set of stimuli. Both encoding and reconstruction accounts of this central-tendency effect are considered. Plain vertical lines and vertical lines embedded in the Muller-Lyer illusion were estimated while still in view or from memory. Although bias due to the Muller-Lyer illusion remained constant across the two conditions, bias due to the contest set (category) occurred only when stimuli were estimated from memory at a later stage of processing than the Muller-Lyer effect and offer support for a reconstruction account of category effects on stimulus estimation.