ABSTRACT: A group of recent, well-controlled ganzfeld studies failed to replicate the positive findings of earlier work (Milton & Wiseman, 1999a). This presents a challenge to claims that a ganzfeld psi effect can be replicated across experimenters under methodologically stringent conditions. Because of the ganzfeld's history as a focus for proof-oriented questions, this situation has implications for parapsychology as a whole. In this paper, it is shown that replication of effect size in the recent ganzfeld studies is not demonstrated across experimenters, regardless of whether the database is updated to include recent studies or whether outcome and cumulation statistics different from those preplanned are applied. Problems with interpreting as strong evidence for psi other parapsychological mets-analyses of less clearly well-conducted studies and apparently consistent process-oriented findings are discussed. The case is made for continuing with ganzfeld research as an important focus of parapsychology's cla ims for replicability. It is argued that if there isa replicable ganzfeld psi effect, however, the procedures necessary to produce it have not yet been identified. It is proposed that process-oriented work be directed to the goal of identifying which studies should be able to replicate an above-chance effect, and that these studies, identified by their planned procedures before they have been conducted, should provide the basis for future tests of replication.
The organization of an international, electronic-mail discussion of these issues among 41 researchers with a special interest in ganzfeld research is described. The edited transcript of the discussion is presented in Part II.
Despite the field's long history, there is still controversy over whether the results of parapsychology experiments offer evidence for a genuine communication anomaly--psi. For some time, parapsychologists have recognized that the evidence for psi most likely to convince fair-minded but critical scientists would be an experimental procedure that a range of experimenters could carry out that would produce reasonably replicable effects. Unless the experiment's effects could be replicated across experimenters, there would always remain fraud, error, or sensory leakage as strong alternative explanations to the psi hypothesis.
For many years, such replicability appeared to be out of reach. This perception appeared to change however, with the arrival in the 1970s of several research programs involving free-response ESP. In particular, ganzfeld ESP studies seemed especially promising. Not only did a range of experimenters appear to obtain outcomes in ganzfeld studies that were above chance, but they did so under conditions that appeared to be well-controlled and without using specially selected participants. In 1981, Ray Hyman, a psychologist skeptical of the existence of psi, wanted to conduct a critical assessment of a research program that represented parapsychology's strongest evidence. Because of claims then being made for ganzfeld research, it was an obvious choice for his attention (Hyman, 1985). Hyman (1985) meta-analyzed the 42 studies conducted since publication of the first ganzeld ESP study in 1974, finding an overall statistically significant outcome; however, he concluded that the methodological problems that he identi fied in the studies could account for the positive results. In response, Charles Honorton, a proponent of ganzfeld research, conducted his own meta-analysis of the database, restricting his attention to the 28 studies reporting direct hits as an outcome measure (Honorton, 1985). He also obtained a statistically significant overall outcome (see Table 1); but although he conceded that the studies contained potential methodological problems, he did not agree that the problems were sufficient to account for the overall outcome.
Rather than continue to dispute the matter, Hyman and Honorton (1986) instead jointly drew up a set of methodological guidelines for the stringent conduct of future ganzfeld studies, agreeing that the case for psi in the ganzfeld would rely on a broad range of experimenters obtaining positive results under such conditions. …