"Eyelid responses were photographically recorded during: (a) pseudo-conditioning (32 subjects), in which the conditioned stimulus was not presented with the unconditioned stimulus, (b) conditioning (31 subjects), in which the conditioned and unconditioned stimuli were paired in the usual manner, and (c) a visual fixation procedure (31 subjects), in which the unconditioned stimulus was not presented at all. The conditioned stimulus was an increase in illumination; the unconditioned stimulus was a puff of air to the cornea . . … Clear-cut and approximately equal increases in the frequency of eyelid responses were found following pseudo-conditioning, conditioning, and visual fixation procedures . . … The only statistically reliable difference between the responses of the pseudo-conditioning and fixation groups was in their distributions of latencies." (PsycINFO Database Record (c) 2006 APA, all rights reserved)