The psychophysics of J-R-L Delboeuf (1831-1896)

Joseph Delboeuf on time as the mechanism of free will

In the early 1880s, Joseph Delboeuf proposed a little-known but ingenious solution to the problem the law of the conservation of energy poses for free will. When energy is transferred between two bodies, the law of energy conservation requires that the energy before and after the transfer be the same, but it says nothing of the time it must take. If we could delay this transfer, Delboeuf proposed, we could alter the course of matter without compromising the conservation of energy. This article begins by tracing the early history of the conflict between free will and the first law of thermodynamics and by recounting some initial attempts to resolve it. It next describes Delboeuf’s theory and the arguments that were made against it, before situating it with respect to some recent developments in the philosophy and psychology of free will.

Visual illusions and inattention: Their association with adiposity among adolescent girls

The Delboeuf concentric circle illusion is frequently invoked as an explanation for the hypothesized association between dinner plate size and overeating. We examined its association with adiposity among 162 girls, aged 14-18 years. We also examined the association of adiposity with neural and behavioral responses during a separate visual discrimination task. The analysis showed that girls with a body mass index percentile ≥ 85, or with greater triceps skinfold thickness, exhibited less sensitivity to the Delboeuf illusion than girls with normal adiposity. The excess adiposity group also exhibited significantly smaller electroencephalographic responses and more errors during the separate visual discrimination task. In combination, the findings from the two tasks suggest that girls with an elevated body mass are less sensitive to visual cues in their environment. The implications of these findings for weight loss education should be considered.

A tale of two psychologies: The Høffding-Lehmann controversy and the establishment of experimental psychology at the University of Copenhagen

Alfred Lehmann (1858-1921) was the pioneer of experimental psychology in Denmark. He established a laboratory of psychophysics in Copenhagen in 1886 after spending a winter in Wundt's laboratory. Philosophical psychology had been taught for the better part of the nineteenth century at the University of Copenhagen and had enjoyed a positivistic turn with the philosophers Harald Høffding (1843-1931) and Kristian Kroman (1846-1925). Shortly after establishing his laboratory, Lehmann criticized Høffding's theory of "unmediated recognition," which led to a sharp dispute between them on the nature of recognition. It has been claimed that this was a direct cause of Lehmann's slow advance at the University of Copenhagen. Archival sources show that Høffding, though having a very different conception of psychology from Lehmann, was on most occasions supportive of Lehmann and thus played an important role in establishing experimental psychology at the University of Copenhagen. (c) 2009 Wiley Periodicals, Inc.

Thirteen days: Joseph Delboeuf versus Pierre Janet on the nature of hypnotic suggestion

The problem of post-hypnotic suggestion was introduced in 1884. Give a hypnotic subject the post-hypnotic command to return in 13 days. Awake, the subject remembers nothing yet nonetheless fulfills the command to return. How then does the subject count 13 days without knowing it? In 1886, Pierre Janet proposed the concept of dissociation as a solution, arguing that a second consciousness kept track of time outside of the subject's main consciousness. Joseph Delboeuf, in 1885, and Hippolyte Bernheim, in 1886, proposed an alternative solution, arguing that subjects occasionally drifted into a hypnotic state in which they were reminded of the suggestion. This article traces the development of these competing solutions and describes some of Delboeuf's final reflections on the problem of simulation and the nature of hypnosis.