Displacement is a characteristic quality of psi, or anomalous cognition. It defines a statistical or qualitative correspondence between a stimulus and a set of responses that occurs independently of their normally perceptible spatial and temporal relationships. Since its identification as a parapsychological effect, it has informed a number of research approaches into psi, particularly for its psychological meaningfulness.
Early researchers, in the late 1800s, often identified that their participants reported information that, qualitatively at least, appeared to be related to alternative targets, equally shielded from sensory perception as the stimulus assigned to a trial within the confines of the experiment. It was only in 1938, however, that astrophysicist Charles Greeley Abbot (1872-1973) identified displacement as a statistically reliable effect. He observed that his guesses for the identity of cards shielded to his sensory perception were reliably accurate - beyond the predictions of probability theory - not only when scored for trial-response correspondences, but also when the responses were tallied for targets one removed, by trial, from those for which they were assigned. This effect appeared to be psychologically related, Abbot observing that displacement especially occurred in relation to illness and fatigue.
Then Secretary of the Smithsonian Institution, Abbot only ventured to publish his findings anonymously. In a couple years, however, an article appeared in the journal Nature that announced independent discovery of the effect. This article was authored by British researchers, Whately Carington (1892-1947) and Samuel Soal (1889-1975). Carington described how, in his studies of the "paranormal cognition of drawings", statistically significant correspondences occurred not only for assigned targets, but also for targets temporally contiguous with targets. Soal reported the same effect to be evidential in independently conducted card-guessing trials. The British psychologist Robert H. Thouless (1894-1984) reported a set of confirmatory observations in a 1942 article published in the British Journal of Psychology. Following his retirement from the Smithsonian in 1944, Abbot undertook further study of displacement, replicating the effect, and openly claiming authorship of his prior anonymously published study .
Importantly for the statistical validity of the displacement effect, all of these early researchers reported statistically significant displacement while taking the total tested range of stimulus-response correspondences into account. That is, whether or not, over the course of the experiment, participants gave responses significantly identical, or apposite, to the stimulus for that trial, responses indicative of perception were nevertheless consistently given to stimuli independently of the sensory-temporal relationship of their presentation and ostensible availability for response.
Since this time, the terminology concerning the displacement effect has become somewhat more precise. Following Thouless' definitions, the parapsychological literature generally denotes a displacement where a response is equivalent to the stimulus for the next trial as a (+1) displacement. Where the response corresponds to the prior trial, the convention is to refer to a (-1) displacement. Higher order displacements have not often been studied, given early computational limits, and the increased number of hypotheses that the data are asked to support. Ongoing technological and statistical developments have permitted deeper analysis of the effect.
More recent research has pursued the relationship of displacement to psychological factors. Most prominently, studies led by James Crandall, during 1980-2000, suggested that displacement is reliably associated with imagery ability. Crandall, moreover, introduced the term psi-missing displacement effect (PMDE) to denote a match between targets and responses that were significantly below-chance, insofar as they shared the same trial, but that was statistically significant within the +/-1 range. There should, for example, be an average of about 5 hits among 25 guesses of 25 targets, over several runs, where there is an equal likelihood of any target being one of 5 alternatives. Crandall observed, over several studies, with independent confirmation, that correspondences of responses to targets on alternative targets, one removed by trial from the assigned target, occurred especially when there was a significantly below-chance correspondence between responses and the assigned target. Such a pattern of responses had, indeed, been evidenced by Abbot, Soal and Thouless in their own studies. Crandall's identification of PMDE, however, clearly brought together the otherwise disparate data on below-chance scoring for assigned targets with the displacement data, and sought to identify the effect's contingencies.
Some researchers have considered displacement to compromise the evidence for psi: Research should be targeted at overcoming its involvement, thereby increasing the accuracy of psi-based detections and identifications in the manner of ordinary sensory perception. Others have considered displacement, however, to be characteristic of the operation of psi. Psychologist Gertrude Schmeidler, of City College, New York, has modelled psi upon normal perception partly on the basis of displacement. She has argued that the data on displacement show similarities to figure/ground relationships in (normal) visual perception. However, displacement has also demonstrated the uniqueness of psi in the discovery of a "wave of correlation" in parapsychological data. This was first reported in 1992, by Norman Don and associates (University of Illinois, and Kairos Foundation, Chicago). They observed a periodicity of displacement both with respect to their own previously collected data, and in a randomly selected sample of data independently collected by J. G. Pratt and J. B. Rhine at Duke University in the late 1930s. Similarly to Crandall, and supportive of Schmeidler's thesis, they observed that imagery ability had a predictive role in producing the effect.
The displacement effect, in this way, appears to potentially signature the nature of psi, as well as its relationship to normal perception and cognition.