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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.

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