Psi man mascot

Extrasensory Perception (ESP)

The sensitivities described so far can all be explained by normal science (and found in the journal Science, if you look at the citation list on the previous page). They are extra sensory abilities but they are not super­natural. In other words, they do not defy the laws of physics or require as-yet-undiscovered forms of energy.

What is the difference between the phenomena just described and ESP?

By contrast, extrasensory perception or ESP is said to involve forms of energy that cannot be measured. Either that, or they are not yet acknowledged by phys­ical scientists.

There is a problem of definition here. Science can investigate anything that can be measured or detected. If a phenom­enon is real, it must have some effect on reality (by definition) so it must be measurable in some way.

If an ESP phenomenon could be explained as due to a new form of energy, or information transmission, then it would be detectable. In that case (in the view of most scientists) it would cease to be ESP and would be classified as a novel, but not supernatural, form of perception.

Believers in ESP, notably Charles Tart, attribute ESP-like phenomena to psychic energy or psi power. This is said to be a purely mental power that does not involve normal energy or information transfer, except perhaps as little-understood quantum effects.

However, there are no replicable experiments showing psi power. Most scientists would say if psi power exerts no reliable effects on the world and cannot be detected, it does not exist.

Occasionally researchers will publish an account of experimental results that seem to defy probability or normal physics, but these findings can never be replicated. That has been going on for well over 100 years.

The consensus of experimental psychologists against ESP led one proponent of ESP, Charles Tart, to accuse fellow psychologists of Fear of Psi. This, he said, accounted for their inability to accept the phenom­enon.

Non-believers countered that Tart got it backwards. People claiming psi powers were showing placebo effects, measurement effects, and selective reporting, because they have Desire for Psi: an earnest desire to believe in psychic powers.

What accusation did Tart level against most psychologists?

Some psychologists do believe in something like ESP. Many of them point to quantum physics for a possible explanation.

Physicists exploring quantum effects (which occur on a subatomic level) can demonstrate very odd phen­omena. An example is "action at a distance" (measurement of one particle determining the measure­ment of an entangled particle, far away).

However, quantum effects can be demonstrated and replicated under laboratory conditions. The same is not true of psi energy or psi powers. Nor has anybody proposed a testable theory of how quantum effects could influence psychological events.

The closest thing to a psychological theory involving quantum effects is an idea floated by Penrose and Haeroff. They proposed that consciousness might have something to do with quantum activity in microtubules of neurons. There is no support for that theory, at present.

Forms of ESP Studied by Parapsychologists

Parapsychology is the study of subjects like extrasensory perception (ESP) that are outside normal scientific areas of inquiry. ("Para" means "other.") Para­psychologists study several different forms of ESP:

1. Telepathy is the ability to transmit thoughts over a distance or read somebody's mind.

2. Psychokinesis (PK) is the ability to move objects or affect physical processes outside the body through mental effort alone.

3. Clairvoyance is awareness of physical objects or events without sensory cues.

4. Precognition is an ability to see or experience the future.

What are four forms of ESP studied by parapsychologists?

Many parapsychologists are well-trained scientists with sophisticated knowledge of experimental methodology. They are attracted to the unknown, a motivation that drives many other scientists.

Other self-described para­psychologists are less reputable. They argue for astral projection, recall of past lives, ghosts, and other ideas inconsistent with the entire body of scientific knowledge.

Even those ideas would be acceptable to scientists if there was a shred of replicable evidence for them. But there is not.

Consequently, parapsychologists of that variety work outside the realm of science. They are gener­ally not accepted by the para­psychology establishment, which prides itself on experimental rigor.

The more scientifically inclined parapsychologists publish in peer-reviewed journals devoted to the topic. An example is the Journal of Parapsychology.

Fraud and Deception

Fraud in ESP research was distress­ingly common in the mid-20th Century. A noted critic of ESP research, C.E.M. Hansel, docu­mented so many cases of fraud involving psychic powers that he refused to believe any ESP research unless a non-believer could replicate it. That never happened.

In J.B. Rhine's famed Institute for Parapsychology in Durham, NC, researcher Walter J. Levy admitted to tampering with a computerized apparatus to make it look like rats had psychokinetic abilities. One of Levy's associates "ratted" on Levy.

How did Hansel react to cases of fraud in ESP research? What was the Levy affair, at the Rhine Institute?

Jim Davis, an electrical engi­neer who did the computer programming and hardware design for the experiment...said that on more than one occasion he witnessed Levy pulling a plug out of the back of the random generator, causing the equipment to record only "hits" for a period of time.

Levy's data would thus indicate better than chance scores for the rat. Meanwhile, Davis had secretly set up a duplicate set of recordings that confirmed only random stimulations. He and his associates went to Rhine with their findings.

Rhine confronted Levy with the evidence. Levy quickly admitted his guilt and resigned. (Asher, 1975)

Rhine's institute is often cited as a source of valid research proving the existence of ESP. Experts on fraud in ESP research believe otherwise.

cards with symbols
Zener card symbols

Rhine became famous in the 1930s for experiments involving Zener cards: special cards with symbols on the front. In classic experiments, Rhine showed that a divinity student named Hubert Pearce could guess which symbol was on the card at levels far greater than chance.

Hansel visited Rhine's laboratory during those years. He did not observe any cheating, but he also did not see precautions against cheating.

To Hansel that was just as important as actual cheating. It meant the results could easily have been faked. Hansel summarized his findings in a 1966 book, ESP: A Scientific Evaluation.

Why did Hansel find Rhine's earlier reports of ESP unconvincing?

George P. Hansen (not to be confused with Charles E. M. Hansel) wrote about fraud in ESP research in one of the main parapsychology journals, noting that past presidents of the Parapsych­ology Association had little familiarity with the practices of professional illusionists (stage magicians). Non-expert observers could easily be fooled by the same trickery that works for illusionists, Hansen pointed out.

Hansen suggested professional magicians would be valuable allies in monitoring ESP research for fraud. This happened. Magicians such as The Amazing Randi became myth-busters aiming their fire at supposed psychics and telepaths.

Johnny Carson, the late-night TV host who had performed as a magician, invited Israeli psychic Uri Geller to his program in 1973 to demonstrate psychic powers. Carson took simple precautions to prevent cheating, such as not letting Geller's people handle the materials of the demonstration before the show.

Geller appeared on the show, prepared to start his demonstration of psychic powers, then broke it off, saying his powers were not strong that night. (The segment is available on YouTube.) Nevertheless, Geller's career as a psychic thrived for years thereafter. People want to believe.

Selective Reporting

Scientists try to publish results when they find a statistically significant effect. However, if they cannot find an effect, the results are ambiguous.

Perhaps the effect they tried to document does not exist. Perhaps their measurement procedures were inadequate. The research typically remains unpublished, sitting in the researcher's file drawer.

This is called the file drawer effect. Robert Rosenthal, the same Harvard researcher who did decades of research on expectancy, wrote the classic article introducing psych­ologists to file drawer effects (Rosenthal, 1979).

What are file drawer effects?

J. B. Rhine, the Duke ESP researcher, had a literal file drawer effect operating in his laboratory. Rhine believed strongly in ESP, and he was suspicious that subjects who produced very low scores on ESP tests were deliberately trying to frustrate him.

Cromer (1993) reported that Rhine kept an envelope in his desk where he stored data sheets of subjects who produced "purposely low scores." Of course, subjects who produced high scores were counted! The net effect was to create an appearance of positive results over the long term.

Problems Replicating ESP Findings

Perhaps the single most powerful argument against the existence of ESP is that no demonstrations of ESP have been repeated in independent laboratories by non-believers. As Padgett and Cody (1984) put it several decades ago, "The world is still waiting for a replicable demonstration of 'psi'."

What is "the single most powerful argument against the existence of ESP"?

Has there been any progress toward "proving ESP" since Padgett and Cody made their statement in 1984? Some psychologists believed that experiments using a ganzfeld provided evidence of ESP.

In a ganzfeld experiment, one individual looks at a picture and tries to send it by telepathy to an individual surrounded by a blank, stimulus free environment (called a ganzfeld). So this is a form of remote viewing.

After methodological criticisms of early ganzfeld experiments, Hyman and Honorton proposed a computer controlled version of the experi­ments. They called this "autoganzfeld" and suggested it would eliminate multiple sources of error.

The result was a flurry of ganzfeld results, some claiming to show small significant results. In 1994, Bem and Honorton published a meta-analysis of these experiments showing, they claimed, a small but genuine ganzfeld effect.

The computerization of ganzfeld research helped to remove some methodological problems involving experimenter and measurement effects. However, the threat of a file-drawer effect still lingered. When data was re-examined with that in mind, the ganzfeld effect disap­peared.

In 1999, Milton and Wiseman published an article in Psychological Bulletin titled, "Does Psi Exist? Lack of Replication of an Anomalous Process at Information Transfer." They wrote:

The new ganzfeld studies show a near-zero effect size and a statistically nonsignificant overall cumulation... The autoganzfeld results have not been replicated by a "broader range of researchers." The ganzfeld paradigm cannot at present be seen as constituting strong evidence for psychic functioning.

For believers in ESP to rebut criticisms, they must eventually present evidence that can be replicated by anyone, including skeptics. That is a basic standard for science as a whole.

Another attempt to provide replicable evidence was published by Daryl Bem in 2011. His report claiming success in demonstrating precognition.

CSICOP, the organization publishing The Skeptical Inquirer, published a devas­tating review of it (Alcock, 2011), saying "careful scrutiny of [Bem's] report reveals serious flaws in procedure and analysis."

Bem (2011) published a rebuttal, noting that his publication appeared in a prestigious refereed journal, the Journal of Personality and Social Psychology (JPSP), and that reviewers seemed to think well of it. Bem invited other researchers to replicate his findings. He even offered to provide them with the necessary software.

Several of Bem's critics took Bem up on his invitation, but they could not replicate his findings (French, 2012). A group of researchers (Galak, LeBoeuf, Nelson, and Simmons, 2012) complained publicly when JPSP, which published Bem's paper, refused to publish their paper reporting failures of replication.

JPSP relented and published the paper. As CSICOP reported (Frazier, 2013):

The article is lengthy, but the central conclusion is succinctly stated:

"Across seven experiments (N= 3,289), we replicate the procedure of Experiments 8 and 9 from Bem (2011), which had originally demon­strated retroactive facilitation of recall. We failed to replicate that finding." They further conducted a meta-analysis of all replication attempts of the Bem experiments "and find that the average effect size (d=0.04) is not different from 0."

To put it even more directly (from the beginning of their conclusions section): "We conducted seven experiments testing for precognition and found no evidence supporting its existence."

...They end by quoting philosopher of science Karl Popper: "An effect is not an effect unless it is replicable, and a science is not a science unless it conducts (and values) attempted replications." They do compliment Bem for encouraging the independent replication of his experiments. (Frazier, 2013)


Alcock, J. (2011, January 6) Back from the future: Parapsychology and the Bem affair. Skeptical Inquirer. Retrieved from:

Asher, J. (1975, November) Can parapsychology weather the Levy affair? APA Monitor, p.4.

Bem, D. J. (2011, January 31). Feeling the future: Experimental evidence for anomalous retroactive influences on cognition and affect. Journal of Personality and Social Psychology. Retrieved from: doi:10.1037/a0021524

Bem, D. J. (2011, January 6) Response to Alcock's 'Back from the Future: Comments on Bem.' Skeptical Inquirer. Retrieved from:

Bem, D. J. & Honorton, C. (1994) Does psi exist? Replicable evidence for an anomalous process of information transfer. Psychological Bulletin, 115, 4-18.

Cromer, A. (1993) Pathological science: An update. Skeptical Inquirer, 17, 400-407.

Frazier, K. (2013) Failure to replicate results of Bem parapsychology experiments published by same journal. Skeptical Inquirer, 37. Retrieved from:

French, C. (2012) Precognition studies and the curse of the failed replications. The Guardian. Retrieved from:

Galak, J., LeBoeuf, R. A., Nelson, L. D., & Simmons, J. P. (2012). Correcting the past: Failures to replicate psi. Journal of Personality and Social Psychology, 103, 933-948.

Hansel, C. E. M. (1966) ESP: A Scientific Evaluation. New York: Charles Scribner's.

Hansen, G. P. (1990) Deception by subjects in psi research. Journal of the American Society for Psychical Research, 84, 25-80.

Milton, J. & Wiseman, R. (1999) "Does Psi Exist? Lack of Replication of an Anomalous Process at Information Transfer." Psychological Bulletin, 125, 387-391.

Padgett, V. R. & Cody, S. (1984). Parapsychology. Science, 223, 1014.

Rosenthal, R. (1979) The 'File Drawer Problem' and tolerance for null results. Psychological Bulletin, 86, 638-641.

Write to Dr. Dewey at

Don't see what you need? Psych Web has over 1,000 pages, so it may be elsewhere on the site. Do a site-specific Google search using the box below.