Alice through the crooked glass

Not Exactly Rocket Science covers a fascinating study where participants felt they were the size of a doll or had expanded to giant proportions simply by using a headset, a camera and a bit of foot stroking.

In a typical experiment, a volunteer is being stroked while wearing a virtual reality headset. She’s lyng down and looking at her feet, but she doesn’t see them. Instead, the headset shows her the legs of a mannequin lying next to her.

As she watches, Bjorn van der Hoort, one of Ehrsson’s former interns, uses two rods to stroke her leg, and the leg of the mannequin, at the same time. This simple trick creates an overwhelming feeling that the mannequin’s legs are her own. If the legs belong to a Barbie, she feels like she’s the size of a doll. If the legs are huge, she feels like a 13-foot giant.

Van der Hoort performed this illusion on almost 200 people. Questionnaires revealed that they did indeed think of the mannequins as their own body parts. Familiar objects didn’t break the spell. When van der Hoort threatened the mannequins’ legs with a knife, the volunteers’ skin broke into a worried sweat, as if their real bodies were in danger. If he touched the doll’s legs with a pencil or his finger, the recruits thought they were being prodded by giant objects. Rather than feeling like dolls in a normal world, they felt like normal people in a giant world.

The researchers Not Exactly Rocket Science dub this the ‘Alice illusion’ after the changes in size experienced by the heroine in Alice in Wonderland.

These experiences can also be experienced as part of ‘Alice in Wonderland Syndrome’ which is usually associated with migraines or epilepsy (although they can occur without any brain disorder) likely due to them affecting the brain’s system for understanding the body’s relation to the surrounding space.

Temporary body-warping experiences are being created in the lab, however, in healthy normal folks and with surprisingly simple tricks.

The Not Exactly Rocket Science piece covers the latest delightful example.
 

Link to NERS on the ‘Alice illusion’.
Link to full text of scientific study.

Hearing the voices of colours

A spectacular case of psychosis, rather oddly described as ‘Methamphetamine Induced Synesthesia’, in a case report just published in The American Journal on Addictions.

The report concerns a 30-year-old gentleman from the Iranian city of Shiraz with a long-standing history of drug use who recently started smoking crystal:

Six months PTA [prior to admission] (October 2009), he started smoking methamphetamine once a day, and gradually increased the frequency to three times a day.

Two months PTA (January 2010), he developed symptoms of auditory and visual hallucinations (seeing fairies around him that talked to him and forced him to conduct aggressive behavior), self-injury, and suicidal attempts.

He developed odd behaviors such as boiling animal statues. He was hearing the voices of colors, which were in the carpet. Colors moved around and talked to each other about the patient. He also saw the heads of different kinds of animals gathering on a board, and they talked to him.

Finally, his mother brought him to the emergency room of Ebnecina Psychiatric Hospital in Shiraz.

The authors are using the term ‘synaesthesia‘ very liberally as it usually refers to an experience in one sense automatically triggering sensations in another – such as numbers having specific colours or tastes.

I’m not sure that ‘hearing the voices of colours’ necessarily qualifies as this could as much a delusion (a distorted belief) or a hallucination (that isn’t specifically tied to seeing the colours) rather than a genuine synaesthetic experience.

As the authors didn’t investigate any further and only have the gentleman’s word for his experiences, it’s a little hard to say.

However, it’s also worth noting that our concept of synaesthesia is no longer tied to ‘crossing of the senses’ as synaesthesia for increasingly meaningful things is being discovered.

Only recently, two confirmed and tested cases of ‘swimming-style synesthesia’ were reported in the journal Cortex where different colours were reliably triggered by the sight of people doing different swimming strokes.
 

Link to locked case report of ‘meth-induced synaesthesia’.

Poetic sensitivities

Perceptual psychologists have long been interested in limen – the threshold at which a stimulus becomes detectable. The following limen for the different senses, expressed in everyday terms rather than in terms of physical quantities, have a certain poetry to them. I got this information via email as a scan of an (unknown to me) textbook. I reproduce them here for your enjoyment:

Approximate absolute sensitivities, expressed in everyday terms:

Vision – A candle flame seen at 30 miles on a dark, clear night
Hearing – The tick of a watch under quiet conditions at 20 feet
Taste – One teaspoon of sugar in two gallons of water
Smell – One drop of perfume diffused into the entire volume of a three-room apartment
Touch – The wing of a bee falling on your cheek from a distance of one centimeter

Exact values vary between individuals and even from moment to moment with the same individual. Source: Galanter, E. (1962). Contemporary psychophysics. Holt, Rinehart, Winston.

A misperceptive critic

It’s not often that hallucinations indulge in media criticism, but this case of Charles Bonnet syndrome recently published in the journal Optometry is a delightful exception.

Everyone, it seems, is a critic, including perceptual distortions generated by, in this case, macular degeneration.

A 79-year-old man presented to the clinic with intermittent hallucinations of 6 months’ duration before this visit. He reported it occurred mostly in the evening, when he saw visions of road maps, Christmas wreaths, and faces that blocked his television screen. The faces were not of people known to him and often had elaborate hats or headdresses. When he rode in a car, he often saw houses that he knew were not truly present, and when he watched his favorite celebrity television dancing show, he saw multiple dancers rather than the 2 actually dancing. He was not disturbed or frightened by these hallucinations; he knew that they were not real. On the contrary, he felt they were amusing and reported they were often more entertaining than what was actually on television.

 

Link to PubMed entry for case report.
Link to DOI entry for same.

An illusory tribute

Richard Gregory was a much loved and hugely influential perceptual psychologist who passed away earlier this year.

Tom just alerted me to a wonderfully appropriate visual palindrome on his page of remembrance where his name reads perfectly well when either the ‘right way up’ on when ‘turned on its head’.

If you can’t see it or don’t believe it, go to the site and click the corner to see the image rotate.

A small but charming tribute to a man who used visual illusions to demystify perception.
 

Link to Richard Gregory tribute site.

The vision thing

The ever-interesting Oliver Sacks is interviewed on NPR’s Fresh Air where he discusses cases from his new book on the extremes of visual perception.

If you’re a fan of Sacks’ work, like me, this programme is an absolute treat as the conversation ranges from the science of misrecognition to his own quite recent experiences of visual distortion caused by a type of tumour, a melanoma, which developed in his eye.

Needless to say, there are plenty of interesting diversions on the way and some quite personal moments interwoven with discussion on themes from The Mind’s Eye – which is apparently out today.

The NPR website has an excerpt from the book if you want a taster and Sacks is also about to start a brief book tour hitting a few cities in the US.
 

Link to NPR interview with Oliver Sacks.