Skin Conductance Prestimulus Response Analyses, Artifacts and a Pilot Study
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Plain English Summary
Can your body sense what's coming before it happens? This unusually rigorous study tested "presentiment" -- the idea that our nervous system reacts to events a few seconds before they occur. Instead of using emotionally charged pictures (where personal reactions muddy the waters), they blasted participants with a startling 97-decibel sound on random trials. A true random number generator decided audio-or-silence only after the body's pre-response window was already recorded, eliminating any subtle cueing. Among 125 first-time participants, skin conductance responses (tiny sweat-gland changes reflecting arousal) were significantly higher before the loud sound than before silence. The really clever part: they ran 125 sessions with a light-sensing gadget standing in for a human, and it showed zero effect -- confirming the result isn't some equipment glitch. People who were naturally more physiologically reactive showed stronger presentiment, echoing earlier research on emotional responsiveness and psychic performance.
Research Notes
One of the most methodologically rigorous presentiment studies in the library. Innovated by using audio startle instead of IAPS pictures, eliminating idiosyncratic stimulus responses. Demonstrated that phasic SCR, not tonic SC level, drives the prestimulus effect. The pseudo-participant hardware simulation (CdS photoresistor) control is unique in the presentiment literature. Post hoc lability-performance correlation (r=0.472) parallels Braud & Schlitz (1983) EDA findings.
Previous studies have suggested that the human autonomic nervous system responds to stimuli 2-3 seconds before presentation, using pictorial stimuli with varying affectivity. This study innovates by replacing photographs with 97-dB audio startle stimuli to avoid idiosyncratic responses, and by using a true random number generator (electron shot noise) sampled after prestimulus data were recorded. 125 first-time participants each received 20 stimuli per session (50% audio, 50% silent control). The primary analysis found a significant difference in the proportion of skin conductance responses before audio versus control stimuli (Z = 3.27, ES = 0.0901, p = 5.4 x 10^-4). Extensive artifact controls including expectation analysis, RNG autocorrelation testing, independent code verification, and a 125-session pseudo-participant simulation all yielded null results, supporting a genuine prestimulus response.
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- Predictive Physiological Anticipation Preceding Seemingly Unpredictable Stimuli: A Meta-Analysis — Mossbridge, Julia (2012)
- We Did See This Coming: Response to 'We Should Have Seen This Coming' by D. Sam Schwarzkopf — Mossbridge, Julia A (2015)
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📋 Cite this paper
Spottiswoode, S.J.P, May, E.C (2003). Skin Conductance Prestimulus Response Analyses, Artifacts and a Pilot Study. Journal of Scientific Exploration.
@article{spottiswoode_2003_skin,
title = {Skin Conductance Prestimulus Response Analyses, Artifacts and a Pilot Study},
author = {Spottiswoode, S.J.P and May, E.C},
year = {2003},
journal = {Journal of Scientific Exploration},
}