Psychophysical interactions with a double-slit interference pattern

Previously reported experiments suggested that interference patterns generated by a double-slit optical system were perturbed by a psychophysical (i.e., mind‐matter) interaction. Three new experiments were conducted to further investigate this phenomenon. The first study consisted of 50 half-hour test sessions where participants concentrated their attention-toward or -away from a double-slit system located 3 m away. The spectral magnitude and phase associated with the double-slit component of the interference pattern were compared between the two attention conditions, and the combined results provided evidence for an interaction (effect size = −0.73 ± 0.14, p = 2.4 × 10⁻⁷). One hundred control sessions using the same equipment, protocol and analysis, but without participants present, showed no effect (effect size = 0.04 ± 0.10, p = 0.71). A Fraunhofer diffraction model was used to explore various interpretations of this outcome. This analysis suggested that the distribution of light between the two slits and the horizontal stability of the laser beam were the principle components of the optical system that were perturbed. The second experiment used a duplicate double-slit system and similar test protocol, but it was conducted over the Internet by streaming data to participants' web browsers. Some 685 people from six continents contributed 2089 experimental sessions. Results were similar to those observed in the first experiment, but smaller in magnitude (effect size = −0.09 ± 0.02, p = 2.6 × 10⁻⁶). Data from 2303 control sessions, conducted automatically every 2 h using the same equipment but without observers showed no effect (effect size = −0.01 ± 0.02, p = 0.61). Distance between participants and the optical system, ranging from 1 km to 18,000 km, showed no correlation with experimental effect size. The third experiment used a newly designed double-slit system, a revised test protocol, and a simpler method of statistical analysis. Twenty sessions contributed by 10 participants successfully replicated the interaction effect observed in the first two studies (effect size = −0.62 ± 0.22, p = 0.006).