On neural signals that mediate brightness

The brightness of any single light depends on other lights in view. These experiments examine how adapting light affects the brightness of a small incremental patch. The original purpose was to determine the quantitative effect of adaptation on the eye's brightness signal for the increment. However, this was found to be a fruitless enterprise because the results showed there exists no single signal from the eye that encodes brightness of the increment. This means that binocular brightness cannot be explained by any model that combines a signal from the left eye and a signal from the right eye. Instead, at least two independent neural signals from each eye are transmitted to a central locus where multi-attribute information about the complete left-eye stimulus configuration is combined with multi-attribute information about the right-eye stimulus configuration.