Fig. 1. Transmission spectra of the three filter types used in the three experiments. Lee UV- (lights) refers to the flexible Lee 226 UV-blocking filter used to remove UV wavelengths from the ambient light by covering the light sources; this occurred in probe trial 2 of experiments 1, 2 and 3. UV+ (patterns) and UV- (patterns) refer to the UV-transmitting and UV-blocking solid Perspex filters used to cover the training stimuli, respectively.