You must turn off your ad blocker to use Psych Web; however, we are taking pains to keep advertising minimal and unobtrusive (one ad at the top of each page) so interference to your reading should be minimal.

If you need instructions for turning off common ad-blocking programs, click here.

If you already know how to turn off your ad blocker, just hit the refresh icon or F5 after you do it, to see the page.

Psi man mascot

Summary: Extra Sensory Perception

Natural but unusual forms of sensory ability include infrared sensitivity (sensitivity to radiant heat), magnetic sensitivity (which has been demonstrated in pigeons and salamanders but not humans), and sensitivity to microwaves (which can heat the bones around the cochlea, producing a crackling sound).

Experiments in the 1980s showed that blind humans could reach out and touch objects in their visual field. Called blindsight, this ability might be due to a visual circuit regulating eye movements that runs through the super colliculi of the brain, separately from the optic nerves.

Distinct from the preceding sensitivities is "extrasensory perception" or ESP. Four classic ESP abilities are telepathy (the ability to transmit thoughts), psycho­kinesis (the ability to move objects using thought alone), clairvoyance (awareness of physical objects or places without sensory inputs), and precognition (ability to see or experience the future).

Such phenomena seem to require modes of information transmission unknown to science. Para­psychologists refer to psi energy, a purely mental energy.

Scientists tend to prefer alternative explanations of ESP-like events, using known forms of energy transmission. Scientists would be swayed if a replicable demonstration of ESP could be discovered. So far, this has not occurred.

ESP-like experiences can be produced by non-supernatural phenomena. For example, the déjà vu sensation is often interpreted as a memory for a dream predicting the present moment.

Selective reporting could be the basis of many reported ESP-like effects. Premonitions (strong worries about disasters to come) are forgotten if they do not come true, but if they happen to be upheld, they are remembered forever.

Selective reporting also operates through the file-drawer effect. This is the tendency of "no effect" research studies to stay in a scientist's file drawer, rather than being published. Several ESP-related results, such as Bem's ganzfeld studies, seem to have been affected by this type of selective reporting.

Perception without awareness is a possible source of many ESP-like experiences. We are influenced by many information sources that never enter attention.

Anniversary phenomena provide one example: they occur when a person makes contact during a certain time of the year. This can lead to uncanny coincidences where person A thinks of person B right before being contacted.

Subliminal effects involving truly unde­tectable stimuli do exist, but they are extremely short-acting (around a tenth of a second, for word priming). Most reports of subliminal influences are mythical.

Examples are the "Drink Coke" experi­ment (which never occurred), subliminal suggestion tapes (which do not work) and hidden symbols of sex and death in advertisements (the subject of a bestselling 1957 book). No lasting effects of undetectable stimuli have been found.

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.