Academic journal article The Journal of Parapsychology

Managing the Target-Pool Bandwidth: Possible Noise Reduction for Anomalous Cognition Experiments

Academic journal article The Journal of Parapsychology

Managing the Target-Pool Bandwidth: Possible Noise Reduction for Anomalous Cognition Experiments

Article excerpt

Effect sizes from forced-choice experiments are much lower than those from free-response studies. For example, in precognition (Honorton & Ferrari, 1989) and real-time (Honorton, 1975) forced-choice experiments, the effect size (i.e., z/[square root of n]) is 0.02, whereas in the free-response ganzfeld (Bem & Honorton, 1994), the effect size is 0.159. Even if we consider the ganzfeld response as a "forced-choice" among four alternatives, the [Pi] effect size, which converts 1-in-n into an effective binary-choice hitting rate (Rosenthal, 1991; Rosenthal & Rubin, 1989), is 0.5123 [+ or -] 0.0004 for card guessing and 0.5854 [+ or -] 0.0287 for the ganzfeld (t([approximately equal to]2 x [10.sup.6] = 46.2, p [approximately equal to] 0). The large t score is probably due to the large number of forced-choice trials (i.e., 2 x [10.sup.6]). Considering that the mean of the forced-choice effect size is 2.5[Sigma] smaller than that of the ganzfeld, however, there is clearly a meaningful difference. One potential source of noise in forced-choice experiments, particularly when trial-by-trial feedback is given, is memory of the previous trial and knowledge of the complete set of possibilities. For example, suppose a receiver (i.e., participant, subject) is asked to guess if a particular card from a normal deck of playing cards is red or black. Suppose further that there is some putative information coming either from the card or from the mind of a sender and that the receiver is a "good" imager (i.e., can easily picture a brilliant image of a playing card in his mind). The receiver's task, then, can be reduced to simple signal detection. Yet, if anomalous cognition (AC)(1) is not a robust information-transfer mechanism (and it appears that it is not), the "signal" is easily lost among the vibrant internal imagery from the memory of all alternative playing cards. The resulting effect sizes, therefore, are reduced.

The ganzfeld itself was developed as a somatic-sensory noise reduction procedure (Honorton & Harper, 1974). Honorton argued that by placing a receiver in a sensory-reduced environment, the receiver's reactions to the environment would be sharply reduced, encouraging a commensurate reduction of noise. On the basis of results from our current work, we argue that a major contributor of noise in any free-response study is cognitive and arises, in part, because of the target-pool design.

One result from the ganzfeld experiments suggests that dynamic targets produce stronger results than do static targets (Bem & Honorton, 1994). Lantz, Luke, and May (1994) attempted to replicate this finding in two lengthy experiments in 1992 and 1993. The first of these explored, in a 2 x 2 design, the relationship between sender versus no-sender and static-versus-dynamic target type on the quality of the AC. Because Lantz et al. reported no significant effects or interactions as having been due to the sender condition, we will ignore that aspect of this first experiment. In the second experiment, they conducted all trials without a sender and changed the characteristics of the target pool. This paper describes the insights gained from these two studies, which led both to the concept of target-pool bandwidth, and to a potential way of reducing noise in free-response AC.


We begin by summarizing the experiment and pertinent results from a study that was conducted in 1992, the details of which may be found in Lantz et al. (1994). In the experiment, a static-versus-dynamic target condition was included to replicate the findings from the ganzfeld.

Target Pools

For the static targets, Lantz et al. used a subset of 50 of our traditional collection of magazine photographs (May et al., 1990). These targets had the following characteristics:

Topic homogeneity. The photographs contained outdoor scenes of settlements (e.g., villages, towns, cities), water (e. …

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