The effect of manipulating expectations both before and during a test of ESP

Journal of Parapsychology, The, Spring, 2004 by Janet A. Pitman, Nicholas E. Owens

Numerous studies have examined various psychological correlates of extrasensory perception (ESP) scores, such as personality traits (e.g., Palmer, 1978). One relationship that has proved to be fairly robust is the association between belief in ESP and performance on ESP tests. Schmeidler and colleagues (Schmeidler, 1943, 1952; Schmeidler & McConnell, 1958) first performed a series of experiments that demonstrated the relationship between belief in ESP and ESP performance. Schmeidler defined goats as those participants who believed that ESP was impossible under the conditions of the experiment, and defined sheep as all participants who were not goats. He found that sheep generally performed above chance whereas goats generally performed below chance. This performance differential has since been labelled the sheep-goat effect (see Haraldsson, 1975; Lawrence, 1993; Palmer, 1971).

The sheep-goat effect can be viewed as an example of the influence of an attitude on behaviour. This attitude/performance relationship is well documented in the psychological literature (Rosenberg & Hovland, 1960; Zanna & Rempel, 1988). An interesting finding from the attitude literature is that attitudes formed by direct personal experience are better predictors of behaviour than attitudes formed by indirect experience (Fazio & Zanna, 1981). Also, these personal attitudes are more specific and stable over time (Fazio & Zanna, 1978; Zanna & Fazio, 1982). Indeed, a common reason given for belief in the paranormal is personal experience (Blackmore, 1984). Bearing this literature in mind, it seems possible that existent attitudes can be influenced through the direct manipulation of experience. Some studies have attempted to manipulate subject expectancies as part of the experimental setting. For example, Smith, Foster, and Stovin (1998) gave participants either a pro-paranormal statement, an anti-paranormal statement, or no statement, and found that the subsequent pattern of belief scores reflected the valence of these statements. Those who had read a pro-paranormal statement produced the highest belief score, and those who had read an anti-paranormal statement produced the lowest belief score. The authors concluded by suggesting that believers in a sceptical context and disbelievers in a pro-paranormal context may show depressed performance on subsequent tasks, due to low motivation to perform.

Other studies have measured the effects of manipulating expectancies on performance with ESP tasks. Akolkar (1968) gave participants a lecture on ESP in either a positive or a negative light and found that participants' attitudes towards parapsychology were significantly affected as a result. Furthermore, Akolkar found that those exposed to the positive evaluation of parapsychology performed better on a subsequent ESP test than those given the negative presentation. Taddonio (1975) also manipulated attitudes prior to testing and found an effect for experimenter-induced expectancy, with better performance on an ESP task for those in the high expectancy group. J.B. Rhine (1945) also found that administration of certain substances such as caffeine directly influenced ESP performance, as did the administration of a placebo. These results are consistent with the view that participants' ESP performance had been manipulated by altering their expectations.

Manipulation of perceived ESP performance during an ESP test has also been hypothesised as being able to alter the belief and performance of participants (Tart, Palmer, & Redington, 1979; Thorisson, Skulason, & Haraldsson, 1991; Woodruff & Murphy, 1943). This manipulation has generally taken the form of feedback during the ESP test. Both Woodruff and Murphy (1943) and Tart et al. (1979) found that accurate feedback as to whether each guess was correct or incorrect was related to ESP performance. In an extension of this paradigm, Thorisson et al. (1991) included false feedback as a manipulation. Participants were asked to guess which of four identical boxes appearing on the screen had been selected by the computer. One group was given correct feedback; they were told whether or not they had guessed correctly on each occasion. The other two groups were told that they were performing either better or worse than they actually were. Thorisson et al. failed to find any significant differences among the performances of these three groups. However, in this study, no explicit reference was made to testing for ESP. Instead participants were asked to participate in a psychological experiment meant to study the relationship between attitudes and guessing abilities. It could therefore be argued that since participants were not aware that they were meant to be accessing a specific ability (ESP), then an increase in perceived performance would not necessarily have led to a better ESP performance.

Tests that aim to influence performance by manipulating belief have sometimes included a third "belief" category into their design (e.g., Thorisson et al., 1991). Bevan (1947) and Casper (1951) both incorporated the category of indecisive into their sheep-goat experiments, referring to those participants who did not hold strong attitudes either for or against the existence of ESP. It has been hypothesised that indecisives are more susceptible to attitudes induced by an experimenter. In an experiment to test this hypothesis Taddonio (1975) found that the effect on performance of experimenter-induced expectancy was indeed most apparent in the indecisive group.