Fisk, G.D., & Haase, S.J. (2007). Exclusion failure does not demonstrate unconscious perception. American Journal of Psychology, 120(2), 173-204.
Elevations in exclusion errors (i.e., responding with the target stimulus despite instructions to the contrary) in experiments with masked, briefly presented stimuli have been attributed to unconscious perception. The present studies were performed to test the validity of exclusion methods for studying unconscious perception. Experiment 1 replicates Merikle, Joordens & Stolz (1995; Experiment 1) by showing increased exclusion errors (exclusion failure) for masked word stimuli in a stem completion task. However, this experiment did not replicate the finding of decreased exclusion errors (exclusion success) at long stimulus durations. Experiments 2 and 3 both show that exclusion errors are accompanied by significant discrimination sensitivity to the target stimulus, which suggests conscious perception of the target stimulus. Experiments 3 and 4 demonstrate that the exclusion errors obtained from stem completion tasks depend, in part, on the methodology. Altogether, the results indicate that findings of elevated exclusion errors do not provide an unambiguous demonstration of unconscious perception.