Extrasensory perception: Does Psi Exist? Psi: “Anomalous processes of information or energy transfer, processes such a telepathy or other forms of extrasensory perception that are currently unexplained in terms of known physical or biological mechanisms.” (Bem & Honorton, 1994, p. 4) The Ganzfeld procedure: Based on the assumption that Psi is usually masked by internal somatic or external sensory “noise.” So, reduce internal and external “noise” through sensory deprivation. Sender concentrates on a visual stimulus selected randomly a large pool of stimuli Receiver provides continuous verbal report of ongoing imagery and thoughts (usually for 30 minutes) At completion of the Ganzfeld period, the receiver is presented with several stimuli (usually 4) and is asked to rate how similar each stimulus is to imagery and thoughts. Hit: when highest rating is assigned to the target stimulus, that is, the stimulus the sender was concentrating on. With 4 alternatives, the hit rate expected by chance is .25. Critique of previous meta-analysis: Half of the studies were conducted by only 2 laboratories: Refuted Selective reporting: Refuted Methodological flaws (sensory leakage, lack of adequate randomization): Some disagreement but mostly refuted Effect size is too small to be of practical or theoretical importance: Refuted Hyman and Honorton’s joint communique: New rules for Ganzfeld research. Strict security precautions against sensory leakage Testing and documentation of randomization methods for selecting targets and sequencing the judging pool Advance specification of the status of the experiment (e.g., pilot study or confirmatory experiment) Full documentation in the published report of the experimental procedure The Autoganzfeld procedure: computer control of experimental protocol videotaped film clips as target stimuli Results across studies: 32% hit rate [equivalent to a coin coming up heads (or tails) 59% of the time]. Art students from the Julliard School in New York were uniquely successful: 50% hit rate. Also highly successful were participants selected on the basis of their psi performance in previous sessions. Sessions using dynamic targets yielded significantly more hits than those using static targets. Friends did not perform better than did strangers. Associations of individual differences with psi performance: Better performance among those who: Belief in psi Have personal psi experiences Are involved with meditation or other mental disciplines Have high scores on Feeling and Perceiving factors on MBTI Are high in extraversion Assuming that psi exists, why does it exist? Noise reduction view: Target information behaves like an external sensory stimulus (like sound or light) that is encoded, processed, and experienced in familiar information-processing ways. Psi-mediated information is conceptualized as a weak signal that is normally masked by internal or external sensory “noise.” Consistent with: Role of receiver characteristics and role of dynamic versus static targets The Role of the Sender: Is the sender needed? Telepathy versus clairevoyance. The Physics of Psi: Bell’s theorem: “Any model of reality that is compatible with quantum mechanisms must be nonlocal: It must allow for the possibility that results of observations at two arbitrary distant locations can be correlated in ways that are incompatible with any physically permissible causal mechanism.” (Bem and Honorton, 1994, p.16) Hyman’s response: Positive hit rate and statistical significance of psi in autoganzfeld experiments is due to dynamic targets. Because this is a new type of stimulus, further replication is required. Results from autoganzfeld experiments are inconsistent with those from ganzfeld experiments. Questions Bem and Honorton’s interpretation of performance by Julliard students and participants who believed in psi. Inadequate testing of randomization procedure leaves door open to alternative explanations. Targets favored by response biases (e.g., water) may have been selected more frequently. Bem’s reply: Hyman overstates inconsistencies and understates consistencies between ganzfeld and autoganzfeld studies: “If the heterogeneity of the original database and the methodological dissimilarities between its variables and those in the autoganzfeld preclude strong claims of consistency [with regard to the role of dynamic pictures], then these same factors preclude claims of inconsistency [with regard to the superior performance of friends].” (p. 26) Additional analyses (e.g., how often was clip rated as target when it was the target as opposed to a decoy) demonstrate that psi cannot be attributed to the conjunction of unequal target distributions and content related response biases.