Results from luminance discriminations with objects defined by apparent mot
ion suggest an object-specific temporal integration of luminance. Further e
xperiments suggested that this integration is weighted to favor the initial
display of an object and involves the percept of surface reflectance (ligh
tness). These results are consistent with the object-file metaphor suggeste
d by D. Kahneman, A. Treisman, and B. Gibbs (1992), in which an object's pe
rceived initial surface reflectance is assigned and maintained in an object
file. A strategy is proposed in which the intrinsic properties of an objec
t are assumed not to change over time. As intrinsic properties are generall
y invariant and possibly difficult to compute, this strategy would have the
advantage of relatively high accuracy at relatively low computational cost
.