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.

Sensory blending

The BBC’s science series Horizon just broadcast a fantastic edition on perception, illusions and how the senses combine with each other to the point of allowing us to integrate artificial new senses.

If you’ve got a healthy interest in psychology, the first half of the programme discusses several important but well-known effects like the rubber hand illusion, colour context changes and the McGurk effect, in light of what they reveal about the perceptual system.

Even if you’re familiar with these concepts, its worth watching as they’re so well presented, but its the second half of the programme which really stands out.

It has several brilliant examples of where people have begun to integrate new information into their sensory world: a blind mountain biker who has learnt to echolocate by making clicks with his mouth, helicopter pilots flying purely by spatial information conveyed to them by vibrations, a belt that allows the wearer to feel where magnetic north is at all times, and so on.

Some of the programme is clearly inspired by an excellent book on unusual sensory and perceptual integration that I’m reading at the moment called See What I’m Saying. It’s by psychologist Lawerence Rosenblum whose name you may recognise as we’ve featured some great pieces from his Sensory Superpowers blog before on Mind Hacks.

If you’re in the UK, you can use the BBC’s iPlayer website to watch the programme online, although rumour has it that there’s a working torrent over at the Pirate Bay.

Link to Horizon edition on BBC iPlayer.
Link to index page of programme on the Pirate Bay.

The ’68 comeback perceptual

Elvis makes a fleeting comeback, accompanied by a milk drinking chimp and some well-dressed mice, in the hallucinations of a patient with Parkinson’s disease who is described in a case study published in the Southern Medical Journal.

He had compulsive gambling behavior and multiple hallucinations (visual and auditory). Visual hallucinations were simple (shapes of shadows, animal shapes like a raccoon, a cat, and a dog) and complex (a woman sitting next to him in car, two well-dressed little mice running around, a chimpanzee drinking his milk standing next to his lunch table in a restaurant, and Elvis Presley standing outside his door in his white coat and white trousers without a guitar). Once while fishing, he saw his dead uncle standing next to him and his uncle said, “It’s not going to work.” Auditory hallucinations were also both simple (incomprehensible sounds) and complex (like his uncle talking to him, nonspecific symphony, and constant melody of chimes). All hallucinations were associated with intact insight and were nonthreatening.

Although the patient was diagnosed with Parkinson’s, which is known to trigger hallucinations, it is likely they were caused as much by the dopamine-boosting medication than by the effects of the disease itself.

The patient was taking quite a selection, reportedly prescribed “a combined regimen including carbidopa/levodopa 25/100 mg four times a day (q.i.d.); carbidopa/levodopa 50/200 mg sustained release three times a day (t.i.d.) with a half tablet in the morning; entacapone 200 mg 5 times a day; pramipexole 1mg q.i.d. with 1.5 mg at bedtime (h.s.); amantadine 100 mg twice a day (b.i.d.); and clonazepam 1mg h.s.”

Despite the perceptual distortions encouraged by the meds, the patient is quoted as saying “It is the best control I have had of my motor functions in a long time” and refused to discontinue any of the treatments.

Link to PubMed entry for case study (via @anibalmastobiza).

Visual science in the art of Chuck Close

I’ve just found this amazing article on the work of artist Chuck Close from a 2008 edition of the Archives of Ophthalmology.

It examines the visual science behind his pixelated style and how a stroke left the artist paralysed – after which he has produced some of his finest work.

Chuck Close (1940- ) is one of the most famous American artists working today. His distinctive paintings are huge canvases that depict faces, often his own. He works in a nontraditional manner by combining many small geometric forms, usually squares or rectangles, to create a portrait. The individual elements he uses in making an image may be termed pixels. The word pixel is a neologism used in computer technology to mean the smallest form in a digitized image and is a combination of the words picture and element.

Chuck Close is a compelling individual who has endured a great physical misfortune. In 1988 he experienced an occlusion of a spinal artery in the neck, which left him quadriplegic. The occlusion has affected the way he paints, but not his style of painting. Many experts have found it difficult to differentiate work done before the onset of his quadriplegia from that done afterward.

The paintings lead to important questions concerning visual perception and the possibility of artificial vision. What determines our ability to combine many small geometric units into a coherent image? How many different elements are needed to create an image? What are the effects of changing colors within the elements?

Close has had a long interest in science, and even painted a cover for the journal Science.

For someone who paints such remarkable portraits, you might be surprised to learn that he recently revealed he has prosopagnosia, a life-long difficulty in recognising faces.

The Archives of Ophthalmology article looks at how we perceive coherent images from patterns that seem chaotic when viewed at close quarters and how Close takes advantage of these processes in his work.

You can click on the images in the article to see them much larger and really get an idea of how they’re constructed.

Link to Archives of Ophthalmology on Chuck Close and visual science.

The strange-face-in-the-mirror illusion

An intriguing article has just been published in the journal Perception about a never-before-described visual illusion where your own reflection in the mirror seems to become distorted and shifts identity.

To trigger the illusion you need to stare at your own reflection in a dimly lit room. The author, Italian psychologist Giovanni Caputo, describes his set up which seems to reliably trigger the illusion: you need a room lit only by a dim lamp (he suggests a 25W bulb) that is placed behind the sitter, while the participant stares into a large mirror placed about 40 cm in front.

The participant just has to gaze at his or her reflected face within the mirror and usually “after less than a minute, the observer began to perceive the strange-face illusion”.

The set-up was tried out on 50 people, and the effects they describe are quite striking:

At the end of a 10 min session of mirror gazing, the participant was asked to write what he or she saw in the mirror. The descriptions differed greatly across individuals and included: (a) huge deformations of one’s own face (reported by 66% of the fifty participants); (b) a parent’s face with traits changed (18%), of whom 8% were still alive and 10% were deceased; (c) an unknown person (28%); (d) an archetypal face, such as that of an old woman, a child, or a portrait of an ancestor (28%); (e) an animal face such as that of a cat, pig, or lion (18%); (f ) fantastical and monstrous beings (48%).

Caputo suggests that the dramatic effects might be caused by a combination of basic visual distortions affecting the face-specific interpretation system.

The visual system starts to adapt after we receive the same information over time (this is why you can experience visual changes by staring at anything for a long time) but we also have a system that interprets faces very easily.

This is why we can ‘see’ faces in clouds, trees, or even from just two dots and a line. The brain is always ‘looking for faces’ and it is likely that we have a specialised face detection system to allow us to recognise individuals whose faces actually only differ a small amount in statistical terms from other people’s.

According to Caputo’s suggestion, the illusion might be caused by low level fluctuations in the stability of edges, shading and outlines affecting the perceived definition of the face, which gets over-interpreted as ‘someone else’ by the face recognition system.

More mysterious, however, were the participants’ emotional reactions to the changes:

The participants reported that apparition of new faces in the mirror caused sensations of otherness when the new face appeared to be that of another, unknown person or strange `other’ looking at him/her from within or beyond the mirror. All fifty participants experienced some form of this dissociative identity effect, at least for some apparition of strange faces and often reported strong emotional responses in these instances. For example, some observers felt that the `other’ watched them with an enigmatic expression – situation that they found astonishing. Some participants saw a malign expression on the ‘other’ face and became anxious. Other participants felt that the `other’ was smiling or cheerful, and experienced positive emotions in response. The apparition of deceased parents or of archetypal portraits produced feelings of silent query. Apparition of monstrous beings produced fear or disturbance. Dynamic deformations of new faces (like pulsations or shrinking, smiling or grinding) produced an overall sense of inquietude for things out of control.

If any Mind Hacks readers try the illusion out for themselves, I’d be fascinated to hear about your experiences in the comments.

Link to full-text of article.
Link to PubMed entry for study.

An Opthamologist on Mars

Oliver Sacks is interviewed on NeuroTribes where he talks about his forthcoming book and his own experience of spectacular hallucinations that occurred after he developed a tumour behind his retina.

NeuroTribes is a new blog by ace science writer and Wired veteran Steve Silberman. It is part of the new PLoS science blog network and in the inaugural post Silberman has scooped a fascinating interview with the great neurologist and raconteur himself.

Here he discusses how his hallucinations, caused by the brain trying to ‘fill in’ or ‘guess’ what should be in the damaged part of the retina, are affected by smoking pot.

I also had — and still have — almost continuous hallucinations of a low order: geometric things, especially broken letters, some of them like English letters, some like Hebrew letters, some like Greek, some runes, and some a bit like numbers. They tend to have straight lines rather than curves, but they rarely form actual words. This is not something I said in the book, but if I smoke a little pot, they sometimes become words. And they tend to be in black and white — but when I smoke a little pot, they’re in color.

Silberman: That’s wonderful. What do the words say?

Sacks: Short English words of no particular significance like “may,” or pseudo-words, like “ont.” Also, since my back surgery last year, I’ve been on nortriptyline, which is supposed to block the gating mechanism for pain in the spinal cord. I only take a small dose, because it gives me an intensely dry mouth. But even the small dose has a striking effect of enhancing dreams and involuntary imagery, and upgrading my hallucinations from black-and-white to color, and from geometric patterns to faces and landscapes.

The interview is both playful and profound and makes a great teaser for his forthcoming book, which apparently, is due out in October.

Link to Oliver Sacks interview on NeuroTribes.