Experimenter Bias and Subliminal Perception

Abstract

It has been suggested that subliminal perception phenomena may be in part due to experimenter bias effects. Two studies that obtained positive evidence of subliminal perception were therefore replicated with experimenters tested under blind and not blind conditions. There was only marginal support for the subliminal perception hypothesis and, although there were fairly clear indications of diffuse experimenter effects, the evidence for the experimenter bias explanation of subliminal perception was not strong. The need for more extensive replications of subliminal perception researches is noted. It is argued that the experimenter bias hypothesis lacks detail and generality; it is essential for it to be examined in the context of theoretically substantial issues.

Perceptual defence: Attempted replication using the dark adaptation paradigm.

“…Instead of obtaining a delay in dark adaptation due to stimulus 'emotionality', our E A s have, if anything, got just the opposite effect. This reversal of the expected outcome not only runs against the perceptual defence hypothesis, but also against the expectations of our GENERAL DISCUSSION One form of negative E bias which was examined in an earlier study (Barber & Rushton, 1975) is that wherein an E exerts a diffusely destructive influence on the effects under investigation. For instance, in a subliminal perception experiment, rather than destroying the selective contribution of the subliminal stimulation, the E could work to obscure that contribution through the injection into the data of additional uncontrolled sources of variation or 'noise'.…”

“…From the present standpoint, the effort to 'eliminate any possibility of the transmission of cues to S', apart from being forward-looking was entirely appropriate, and in fact essential for an unequivocal test of the subliminal perception hypothesis. But since a subliminal perception effect may be produced through occasional cueing based on partial information held by E about the stimuli and the stimulus sequence (Barber & Rushton, 1975), it is important to ask whether this was possible in Worthington's original experiment, despite his very proper safeguards. Evidently E needed to see the label on each slide and since there was a light-adapting apparatus, it seems likely that the laboratory was illuminated for much of the time prior to the presentation of the dark adaptation stimulus.…”

A percept‐genetic study of some defence mechanisms in the PN‐test

“…Furthermore, the experimenter could not be seen or heard by subjects to avoid shaping responses. Response bias is an unlikely determination of the results, as indeed has been shown for subliminal tachistoscopic effects by Barber & Rushton (1975).…”

Perceptual defence: Attempted replication using the dark adaptation paradigm: A rejoinder.

“…Concerning the first point, particular care was taken to copy the source experiment as closely as possible since earlier work seeking to replicate some subliminal perception effects (Barber & Rushton, 1975) had provoked some controversy over how exact a replication should be (Barber, 1977;Spence & Smith, 1977). Nevertheless some changes did occur in the preparation of material and the construction of the apparatus; but these changes were inadvertent, and arguably trivial.…”