Copyright © 2007-2018 Russ Dewey
Could there be more senses beyond the seven we have considered already in this chapter? Certainly there are. If sensation is defined as sensitivity to specific classes of stimuli, then researchers have documented many "extra" sensory capabilities.
However, there is a crucial difference between extra sensory abilities (those in addition to the classic senses we have considered) and extrasensory abilities (those involving "psi energy" or other as-yet unverified powers of the mind). We will consider both categories.
Several forms of sensory detection are outside the normal list of seven senses (visual, auditory, olfactory, gustatory, cutaneous, kinesthetic, equilibratory). These forms of sensory detection are not ESP because they all involve known mechanisms.
Radiant heat sensitivity is highly developed in humans. Radiant heat is infrared radiation. It is electromagnetic radiation, like light, but it is outside the visible spectrum.
The most efficient non-living surface for absorbing heat is black, which is why dark surfaces get hot in the sun. Black surfaces are about 90% efficient in absorbing radiant heat. Human skin (even untanned white skin) is about 95% efficient in absorbing and radiating infrared radiation (Barnes, 1963).
Why should human skin be so efficient in absorbing or radiating infrared? It aids temperature regulation. On hot days, we can radiate heat efficiently; on cold days we can absorb a surprising amount of heat from glowing embers of a small fire.
How could infrared sensitivity lead you to sense that a person has entered the room behind you?
On a cold day in a wintry climate, you can feel a wood stove across the room, or a lightbulb turning on, or a person next to you, just by the heat. This may account for some reports of mysterious intuitions about people entering a room. Even if you cannot see them or hear them, you might feel them.
Sensitivity to magnetic fields is found in many species (Hsu & Li, 1994). Pigeons, for example, have a tiny amount of natural magnetite (magnetic rock) in a crucial place in their brains, enabling them to orient their flight according to the magnetic fields of the earth.
Similarly, salamanders have magnetic sensitivity they can use to find their way around a maze when other cues are removed. When pigeons or salamanders are fitted with caps containing magnets, they lose their navigating ability. This proves magnetism guides them.
Why are pigeons able to detect magnetic fields? How can this be proven?
Humans also have tiny amounts of magnetite in their brains. Do humans have a magnetic sense? For a time it seemed so.
A British researcher named Baker (1980) caused excitement with a report in Science. He said blindfolded subjects released 6 to 52 km away from home were able to point toward home with greater-than-expected accuracy.
The subjects became less accurate when wearing magnets on their heads. That would be expected if they had genuine magnetic sensitivity.
Gould and Able (1981) were intrigued by these results and attempted to replicate them with a sample of 40 Princeton undergraduates and 19 students from SUNY Albany. Baker visited and helped them replicate his original study.
They were disappointed. "Despite the apparent simplicity of Baker's various methods and the consistency of his results, we could not repeat the phenomenon either at Albany or Princeton."
What was Baker's research? What happened when other researchers tried to replicate it?
Kerr (1993) reported that patients with electrodes implanted before surgery showed a distinct response to weak magnetic fields. We know nerve cell activity generates weak magnetic fields; that is the basis of the brain scanning technology called MEG (magnetoencephalography).
Whether magnetic sensitivity in humans has any significance or functional importance has not yet been determined. The magnetite is there, the neural response is there, but no researcher has yet documented a human behavioral response to magnetism.
Joe Kirschvink of the California Institute of Technology has spent over 30 years looking for evidence of human magnetic sensitivity. Pursuing human magnetic sensitivity experiments on the side from his main work, he periodically found enticing results. "But from day to day, we couldn't reproduce them." (Hand, 2016).
In 2016, Kirschvink hinted at promising new results using a Faraday cage. That is an apparatus that removes all outside electromagnetic influences, so subjects could be tested with greater control. Kirschvink and colleagues have a $900,000 grant to look for human magnetic sensitivity, using this new setup, so perhaps replicable evidence will be forthcoming.
Microwaves directed at the human skull can be heard if emitted in pulses. Frey and Coren (1979) reported the theory of a colleague, R.M. White, that microwave-induced hearing is due to thermoacoustic expansion in cochlear structures (expansion due to heat, producing an audible sound).
Thermoacoustic expansion might also explain a rare and exotic phenomenon: the auditory perception of meteorites at long distances. Keay (1980) noted:
...The problem was recognized almost 100 years ago by Sir Charles Blagdon, Secretary of the Royal Society of London. He collected reports of a large fireball and was perplexed by the simultaneous observations of hissing sounds heard as the fireball passed more than 50 miles from the observers....
How might you hear a meteorite that is 50 miles away?
It must be stressed that these anomalous sounds are not to be confused with the normal acoustic phenomena–sonic booms and rumbles–which travel at normal velocities and are heard some time after the fireball has passed the observer. (p.11)
If the visual cortex is damaged by stroke or other injury, patients lose the ability to see things in part of the visual field. The abnormal blind area in the visual field is called a hemianopia (hem-i-an-NO-pia).
Some patients with hemianopias involving as much as half the visual field can nevertheless reach out and touch objects in the blind area. This is called blindsight.
Blindsight is relatively rare. It is not found in every patient with hemianopias. However, blindsight intrigues investigators because it suggests that visual information can find its way into the brain through an unconscious route.
The leading theory of blindsight suggests that visual information reaches the brain through the second visual system in the brain, which runs through the superior colliculi of the brain. The second visual system is a localizing system, specialized for guiding eye movements.
What is blindsight? What is an explanation for blindsight?
The surface of the retina is mapped onto the superior colliculi much the way it is mapped onto the visual cortex at the back of the brain. Both the visual cortex and the colliculi have a map of the retina: a retinotopic map.
When movement occurs in the visual field, the superior colliculi generate an automatic eye movement toward that location. If this circuit is still working in a person who has a damaged visual cortex, the eye movement might be used as a cue to the location of the object.
The second (collicular) visual circuit may "know" more about an object than merely its location. The superior colliculi are richly supplied with incoming fibers from other areas of the brain.
Cells in the colliculi habituate (cease firing) when the same object is presented again and again in the periphery of the field of vision. Yet, after habituation, those same cells respond to a new, unfamiliar object. (This is called dishabituation or release from habituation.)
How do we know pattern recognition occurs in the collicular vision circuit?
So pattern recognition of some type takes place in the collicular pathway. That could result in ESP-like experiences, if activity in the superior colliculus found its way into consciousness through some route, direct or indirect, such as by guiding eye movements.
The unusual sensitivities we have reviewed so far do not begin to exhaust the possibilities. Athenstaedt, Claussen, and Schaper (1982) reported a "pyroelectric and piezoelectric sensor layer" in human skin that allows perception of tiny electric changes similar to those picked up by the electrodes of a lie detector.
It is hard to imagine how this information might be used. But it is another input to the nervous system from sensors not included in the classic seven types.
Human odor sensitivity is more advanced than commonly acknowledged. We also may extract more information from odors than we consciously realize.
Diet and health affects body odor. Sex hormones change body odor. Smokers and drinkers are readily detectable to others because of odor.
Even if odors only correlate with a special condition, they can still yield predictive information. Diet, by itself, could correlate with cultural identity and preferences in subtle ways, and that sort of correlative information could be manifested in intuition.
Recall that one olfactory system is totally unconscious: the vomeronasal system. Yet it provides information that the human brain might use.
How could odor or the sound of breathing lead to intuitions?
Ordinary senses can also supply information that escapes conscious attention. For example, the sound of someone's breathing is plainly audible in a quiet room.
It is also true that diminished vital capacity (the amount of air you can keep in your lungs) is an accurate predictor of coming death, especially in old age. Common disorders like congestive heart failure reduce lung capacity.
However, we do not need to understand the reason for the correlation, or even be aware of the correlation, to use the information as the basis for an intuition. Detection of shallow breathing–or a hundred other clues to ill health–could be the basis for accurate premonitions of death or illness.
How can unconscious knowledge affect decisions?
Carl Jung described intuition as unconscious knowledge. There is much more information in the nervous system than we can represent in consciousness, but that does not mean we cannot use it.
Hunches and intuitions may result from pattern-recognition that operates on an unconscious level. This was the implication of research on unconscious learning, described in Chapter 3.
Athenstaedt, H., Claussen, H., & Schaper, D. (1982). Epidermis of human skin: Pyroelectric and piezoelectric sensor layer. Science, 216, 1018-1020.
Baker, R. R. (1980). Goal orientation by blindfolded humans after long-term displacement. Science, 210, 555-7.
Barnes, R. B. (1963) Thermography of the human skin. Science, 140, 870-877.
Frey, A. H. & Coren, E. (1979). Holographic assessment of a hypothesized microwave. Science, 206, 232-234.
Gould, J. L. & Able, K. P. (1981). Human homing: an elusive phenomenon. Science, 212, 1061-1063.
Hand, E. (2016, June 23) Maverick scientist thinks he has discovered a magnetic sixth sense in humans. Retrieved from: https://www.sciencemag.org/news/2016/06/maverick-scientist-thinks-he-has-discovered-magnetic-sixth-sense-humans
Keay, C. S. L. (1980). Anomalous sounds from the entry of meteor fireball. Science, 210, 11-14.
Kerr, R. A. (1993). Magnetism triggers a brain response. Science, 260, 1590.
Write to Dr. Dewey at firstname.lastname@example.org.