What is the correct dimensionality of paranormal beliefs? A reply to Lawrence's critique of the paranormal belief scale

Journal of Parapsychology, The, March, 1995 by Jerome J. Tobacyk

Lawrence (1995), in his detailed and extensive critique of the Paranormal Belief Scale (PBS) (Tobacyk, 1988; Tobacyk & Milford, 1983), raises a number of issues concerning the nature and measurement of paranormal beliefs. Given practical constraints of time and resources, I will focus on five of these issues: (a) What is the definition of paranormality? (b) Was factor analysis appropriately used in constructing the PBS? (c) What is the dimensionality of the paranormal belief domain? (d) Is Lawrence's critique of the PBS (original and revised forms) accurate? and (e) What is the construct validity of the PBS?

I fully agree with Lawrence that there is a need for improvements in self-report assessment instruments for the measurement of paranormal beliefs. Indeed, it was this conviction that led to the construction of the original PBS and its subsequent revision. Although I agree with Lawrence concerning some of the limitations and weaknesses in the PBS that he has pointed out, I disagree with others of his criticisms. I hope that this exchange will lead to the development of improved paranormal belief assessment instruments with better psychometric properties and with greater fidelity to human experience.

WHAT IS THE DEFINITION OF "PARANORMALITY"?

The definition of paranormality selected by the investigator establishes the boundary of the paranormal belief domain, which, in turn, determines the content of the PBS item pool. Ideally, items are representatively constructed and selected from this item pool. Subsequently, respondents' ratings of these items are factor analyzed, and, via a series of decisions informed by empirical findings, the PBS is constructed and subsequently refined. Thus, the content of the PBS is strongly influenced by the initial definition of paranormality because this definition determines which ostensibly paranormal phenomena are included and excluded from the item pool.

In the research leading to the 1983 PBS, we used three criteria of paranormality: (a) inexplicability in terms of current science, (b) explicability achieved only by major revisions in basic limiting principles of science, and/or (c) incompatibility with normative perceptions, beliefs, and expectations about reality. These three criteria allowed the inclusion of items reflecting a relatively wide range of phenomena, which is reasonable when exploring the dimensionality of a domain. However, since that time I have concluded that Broad's (1949/1978) definition of paranormality (which I slightly modified by using the notion of "low probability," rather than "impossibility," of violating Basic Limiting Principles of Science) is the least problematic and most parsimonious. Consequently, I used Broad's definition in the 1988 paper describing the revised PBS. Although there are problems with Broad's definition (see Braude, 1979), the establishment of a set of consensually agreed upon principles to demarcate the boundaries of the paranormal domain (i.e., Basic Limiting Principles of Science) appears to be a reasonable way to address the "boundary problem" in parapsychology (i.e., what ostensible phenomena should parapsychology study?). For example, surveys of scientists in various disciplines could be used to generate potential Basic Limiting Principles, and some expert consensus could be achieved on those principles that were most satisfactory. Although all Basic Limiting Principles are, admittedly, relativistic and could in fact be invalidated by new discoveries, this is not a devastating criticism because human consciousness does not appear privy to absolute knowledge.

Indeed, as pointed out by Lawrence (1995, pp. 444-445), the definitions of paranormality used in constructing the PBS are problematic, but this limitation is not uniquely characteristic of the PBS; it is, in fact, characteristic of the field (e.g., see Rao & Palmer, 1987, and the associated peer commentary, for discussions concerning this problem). Quite frankly, I fail to see the advantages of Irwin's (1993) definition of paranormality over Broad's (1949/1978). First, I simply disagree with Lawrence's contention that Irwin's definition is "far more restrictive" than either Broad's or mine (1983, 1988). Irwin's definition includes two criteria for paranormality - both "hypothesized processes that in principle are 'physically impossible'" as well as "outside the realm of human capabilities as presently conceived by conventional scientists" (Irwin, 1993, p. 1). Lawrence seems to focus only on the second part of Irwin's definition ("outside the realm of human capabilities as presently conceived by conventional scientists") when classifying only Witchcraft, Psi, Precognition, and Spiritualism as paranormal. However, the first part of Irwin's definition ("hypothesized processes that in principle are 'physically impossible'") clearly includes much of the ostensibly miraculous and magical phenomena of traditional religion and superstition, which is attributed to extrahuman forces (i.e., gods, spirits, souls, ghosts, angels, devils, etc.). Also, I do not see a fundamental difference between Irwin's definition and Broad's Basic Limiting Principles.