"The secret ingredient is hate," -- Dr. Heinz Doofenshmirtz
I had originally planned a short post on the Through the Wormhole episode on the sixth sense, but researching the various claims made has taken up so much time and so many pages that I am breaking into a multi-part (probably 5 part) series of posts. I'm not sure why I've kept working on this since there's no real point to debunking it, and I'm not a professional debunker. But I was annoyed by the episode, and so I think I must have been driven by hate. Here is part 1.
Previously, I had considered Through the Wormhole (TTW) with Morgan Freeman to be Harmless. Today, however, I must downgrade my evaluation to Mostly Harmless.
The episode, "Is there a the Sixth Sense?" crossed over from innocuously speculative and silly science-related program to endorsing highly suspect research with the apparent aim of titillating rather than educating the audience. It appears that TTW is based on real science in the same way that The Amityville Horror was based on true events. In other words, it's not actually true (or science). There might be something true somewhere in there, but there's no way to tell what's true, and the true part doesn't relate to the interesting parts emphasized in the story.
It's a bit silly talking about a sixth sense when the variety of sensory inputs we know about exceeds the traditional five senses already. People have distinct sensors for heat, pain, and pressure; they sense the location and movements of their bodies; they sense various internal facts about their guts. But TTW uses the "Sixth Sense" terminology to appeal to our idea of a sensory apparatus beyond those previously known to science.
Freeman posited several different varieties of sixth sense. 1. TTW reports on visual perception among blind-sighted individuals using a distinct visual system in the brain. 2. It reports on David Chalmers's unusual views on consciousness and the supposed impossibility of reductively explaining it in terms of objective science. 3. It reports on the Global Consciousness Project that claims that humans in large groups have a capacity to affect random number generators so that they cease for brief periods of time to be random and that this shift to non-randomness results from large scale emotional arousal. 4. It reports on psychologist Michael Persinger's claim that people can communicate perceptual information from one mind to another following lines of electromagnetic force. 5. It reports on Rupert Sheldrake's claim that people have an ability to know when they are being watched by others even when they have no ordinary perceptual means of discerning this fact.
Part 1 of my report is limited to the blindsight case.
This fascinating phenomenon occurs when people have damage to visual cortex so that certain parts of their visual fields are "blind", and they appear to lack any conscious awareness of those parts of their visual field. Their eyes are perfectly functional and continue to send information to the brain. Psychologists (led by Lawrence Weiskrantz who discovered this phenomenon) have shown that blind-sighted patients have some surprising abilities. If these subjects are forced to guess about the supposed blind part of their visual fields, they are able to say at a rate better than chance whether there is a light in that field. When they reach for something in the "blind" part of their field, they will shape (apparently automatically) their hands to the object in the field. For example, they will shape their fingers to pick up a coffee cup or a paper clip. They will not volunteer the information that something is in their visual field, and they do not even believe they can see anything. However, they have visual perception even if this is not conscious.
Blindsight is a great hook for a science show since it is wildly counterintuitive that people could see without realizing that they can see. It also provides a great chance to teach about the brain, its complexity and modularity (or distinct paths of processing) and its evolution. Apparently, at some point in its evolution, the brain added new pathways in visual cortex without adapting evolutionarily older pathways. TTW could even have taught about the complexity of visual processing, and that's fascinating in and of itself.
TTW reviews the research of Beatrice De Gelder in the Netherlands who finds that people blind in one side of the visual field will automatically mimic the facial expression of a picture shown only to their blind field and they will show a galvanic skin response for emotionally-charged pictures but none for no pictures or for neutral pictures. This shows that despite damage to certain areas of the visual cortex, people will still be able to take in a certain amount of visual information, specially directed towards the emotional system in the brain, the amgydala and other areas, yet those people will lack any conscious any awareness of or ability to verbalize that information.
Conclusion: Sixth sense fail.
Blind-sight is fascinating. Unfortunately, the episode chose to treat this as more mysterious than it is. TTW repeatedly referred to the field, from one eye, as "blind" as though people could not see at all in that part of the field and then pretended that their ability to acquire this visual information in some mysterious way. Vision, even blindsighted vision, is not a sixth sense; it’s just plain old seeing. However, what this phenomenon shows is that vision is a more complex phenomenon than people might have thought, one that involves conscious and unconscious elements. And it provides an interesting case in which perceptual information is processed without consciousness; we can see (in a certain limited sense) without being aware that we see.
Next up: Part 2 on Consciousness.