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Volume 17: Number 4: Article 2
Skin Conductance Prestimulus Response: Analyses, Artifacts, and a Pilot Study
S. James P. Spottiswoode and E. C. May, Laboratories for Fundamental
Research, 330 Cowper, Palo Alto, CA 94301
Previous studies have suggested that the human autonomic nervous system
responds to stimuli 2-3 seconds before presentation. In these studies
randomly chosen photographs with high and low affectivity were presented
to participants. Ensemble averaging of skin conductance in the prestimulus
epochs showed a differential response between high and low afectivity
photographs. In our protocol the problem of idiosyncratic responses
to pictorial stimuli was avoided by using audio startle stimuli. Stimulus
type was determined just before presentation by a true random generator.
Participants heard 20 stimuli per session with a 50% chance of an audio
startle as against a silent control. Our dependent variable was the
proportions of 3-second epochs prior to audio and control stimuli in
which skin conductance response, that is a minimum in skin conductance
followed by a maximum, occurred. We found a significant effect (N
= 125, Z score = 3.27, effect size [ES] = 0.0901 +/- 0.0275,
p = 5.4 x 10-4). Explanations for this result as an
artifact were examined and rejected. We show that a significant result
from an average-based epoch analysis in this type of experiment is not
a necessary requirement to demonstrate significant evidence for a prestimulus
response. We also observed post hoc that the prestimulus response
effect was correlated with participant lability (r = 0.472, df
= 21, p = 0.011).
Keywords: skin conductance, presentiment, retrocausal, prestimulus
response, precognition
FULL TEXT:
Skin Conductance Prestimulus Response: Analyses, Artifacts, and a Pilot Study
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