The VL concept is based on measurements of accuracy thresholds where r
esponse times are essentially unlimited. Pea has produced a visual per
formance model based on reaction times, which include response times.
Analysis of phenomena such as the Pulfrich illusion suggest that there
is a delay between signal onset and recognition that depends upon the
adaptation luminance. This suggests an analysis of reaction times in
terms of a simple sum of a signal strength (VL) term plus response ter
m(s), including a delay term. A comparison of Pea's reaction-time mode
l and this additive VL model showed that the models are similar, but t
hat the VL model fits the data better and has a more consistent theore
tical foundation. The luminance-dependent response term appears to be
needed to fit performance on the numerical verification task developed
by Pea, but not the word chart reading task developed by Bailey. The
above additive VL model suggests that the difference may depend on whe
ther the task is processed serially and includes the delay time, or is
processed in parallel and does not.