A state of hypnosis creates detectable changes in a person’s eye movement patterns, says a new study.
The “glazed” look of a person who’s been hypnotized can be linked to measurable, quantifiable changes in the patterns of that person’s reflexive eye movements – changes that non-hypnotized people aren’t able to replicate.
The exact nature – and even the actual existence – of the hypnotic state have been controversial topics since the term was first coined in the 1840s. Some have likened it to a form of sleep (the word itself comes from the ancient Greek hypnos, meaning “sleep”), while others have described it as a state of intense focus, or of heightened suggestibility. Some have claimed that hypnotized people are faking, or at least fooling themselves – but even so, the idea of hypnosis continues to fascinate many of us.
One of the first real indicators that hypnosis might be an objectively detectable state came in 1999, when a team at Belgium’s University of Liège used positron emission tomography (PET) scans to detect altered activation patterns in the brains of volunteers under hypnosis. A 2002 study at the University of Montreal lent more detail to these results; and in 2007, a team led by Andrew Fingelkurts at Finland’s Brain and Mind Technologies Research Centre attacked the problem from another angle, using electroencephalography (EEG) to detect changes in electrical activation across the scalps of hypnotized subjects.
The research seemed to suggest that hypnosis might alter the brain’s functional connectivity, preventing certain areas – such as the anterior cingulate cortex (ACC) and the dorsolateral prefrontal cortex (dlPFC), both of which are involved in goal-directed behavior – from communicating with other areas that might inhibit or otherwise modulate their activity. Interestingly, though, these changes were only detectable in “very highly hypnotizable subjects” – implying that belief and willful participation are crucial ingredients in hypnosis.
Now, as the journal PLoS ONE reports, a multidisciplinary team of researchers from Finland’s University of Turku and Aalto University, and Sweden’s University of Skövde, have found what may be even stronger indicators of a physically detectable hypnotic state – changes in various reflexive eye movements.
The team hypnotized a single volunteer (which means these results should be taken with several large grains of salt) and compared her eye movements against those of a control group of non-hypnotized subjects. The researchers found that when their subject was hypnotized, her eyes exhibited some unique behaviors:
[She] showed a markedly reduced eye-blinking rate (0.012 ± 0.04 blinks/s) as compared to [control subjects] (1.18 ± 0.63 blinks/s). Although some control subjects could mimic rather well this external feature of the “trance stare,” at the group level the changes were far less marked.
Even stranger, though, were changes in the subject’s saccades – the rapid, often involuntary eye movements that help us focus on changes in our environment or quickly scan the details of a scene:
[When hypnotized, the subject] performed only short saccades toward the target regardless of the distance from the fixation point. This “creeping” pattern of short saccades was difficult to simulate by the control group since their fixation tended to automatically gravitate to the target.
The subject’s saccades were also much slower, shorter, and fewer than any that non-hypnotized volunteers could produce. In other words, her gaze tended to shift much less, and less often, than the gazes of people in the control group.
Exactly what this data means is tough to say – and not just because it’s only been detected in one volunteer; it’s also not clear what changes in brain activity these unusual eye behaviors might reflect. The researchers have a suggestion, though: the ACC is known to be closely connected with visual brain areas, and to help coordinate saccades. Could these strange saccades reflect changes in the ACC’s functional connectivity?
It’s too soon to say for sure – but it seems that even if hypnosis does depend on willing belief, it still has some objective neurological correlates that are worth studying. It may be that we have much more control over our brains’ functional connectivity than we ever suspected.
Who knows – it could be that even now, someone is implanting subtle cues waiting for the moment when- SLEEEEP!!!