LBNL Report Number
The VL concept is based on measurements of accuracy thresholds where response times are essentially unlimited. Rea has produced a model based on reaction times, which include response times. Analysis of phenomena such as the Pulfrich illusion suggest that there is a delay time between signal 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 term(s). A comparison of Reas reaction time and this additive VL model showed that the models are similar, but that the VL model fits the data better and has a more consistent theoretical foundation.
The luminance-dependent response term appears to be needed to fit performance on the numerical verification task developed by Rea, but not the word chart reading task developed by Bailey. The above additive model suggests that the difference may depend on whether the task is processed serially and includes the delay time, or is processed in parallel and does not.