She's Hearing Voices

If you hear voices that aren't really there, are you "mad"? Maybe - auditory hallucinations, most commonly voices, are one of the characteristic symptoms of schizophrenia and are sometimes also a feature of severe depression and mania. (For more on hallucinations, try this paper. It's long, but it's worth a read because it's one of the few academic papers containing phrases like "Do YOU want a slap in the head?" and "Die, bitch".) But anyone can find themselves hearing things that others don't - it just takes a little prompting.

Via the excellent Mind Hacks, I came across this great little page by Cambridge neuroscientist Matt Davis, which gives some examples of Sine Wave Speech. Essentially, Sine Wave Speech is a voice recording which has been digitally degraded so that it's little more than a collection of beeps and bleeps (sine waves, in fact). When you first listen to it, it sounds something like R2D2 on ecstasy.

However, if you listen to the original, unaltered voice and then go back to the sine-wave version, you can hear the words - the bleeps suddenly sound like a voice. The change is striking - so much so that if you didn't know what was going on, you'd probably think you were listening to a whole new clip. This effect is one example of the brain's tendency to perceive a pattern in a stream of noise, when an expected pattern is known. We're all familiar with this in the realm of vision - if you're looking for something amongst a pile of clutter, your eye is drawn to it, but you won't even register all the other rubbish that's around it. We're not used to the same thing happening with sound, though, I suppose because we generally hear things without much difficulty.

Sine Wave Speech really is a form of voice, but the same principle can lead people to hear voices in the unlikeliest places. Hence the recent case of the Amazing Satanic Islamic Doll, also known by its Jihad name, "Little Mommy Cuddle 'n Coo". This is a kid's toy made by Fisher Price which, when hugged, plays recorded baby noises. A month or so ago a concerned parent somewhere in America decided that one of the recorded baby noises sounded like a voice with a disturbing message. Have a listen.

Did you hear any speech the first time you heard the doll's noise? Probably not, but I'd bet that after you'd heard the claim that the doll was saying "Islam is the Light", the same noise started to sound rather different. After several listens, I now can't hear the noise as anything other than a voice saying that phrase, even though intellectually I know that this is absurd (if Fisher Price were going to plant a message like that they'd be more likely to use "Buy more toys").

The doll is a post-9/11 rerun of the infamous Satanic backmasking scare. If you a play a record backwards, you'll hear various distorted sounds, some of which could be interpreted as speech, if that's what you're expecting to hear. During the 1980s, some concerned citizens (again in America) thought that they could hear Satanic or sexual messages hidden in heavy metal records when they were played backwards. Upon hearing this, several bands liked the idea and actually did put backwards messages in future songs, but most of the allegations were based on people hearing voices in noise, because that's what they expected to hear.

One man believes that the problem goes far beyond metal music and that everyone has hidden backwards messages in everything they say, messages which reveal their subconscious thoughts. Cripes. He gives a lot of examples here. Note that he helpfully tells you exactly what to expect to hear before you've heard to recordings.

Anyway, in original video above, a concerned mom argues that the Muslim message must be real because she can't believe that people across the country are "all hearing things". She doesn't understand that you don't have to be hallucinating to over-interpret noise. It happens to the best of us, and once you know what to expect you really hear the voice, clear as day, whether or not you "believe in it" or "want to hear it". It's not simply the power of suggestion.

On the other hand some psychologists have claimed that suggestion alone can make people hear things. This is generally called the "White Christmas Effect". The original experiment in support of this claim took 78 female students who were told - "in a firm and serious tone of voice" -

I want you to close your eyes and to hear a phonograph record with words and music playing White Christmas. Keep listening to the phonograph record playing White Christmas until I tell you to stop.

As you may have guessed from the language used in sentence, this experiment took place in 1964. Anyway, the students were ordered to hear White Christmas playing in a silent room, and then asked to check a box indicating whether they in fact heard it. 5% said that "I heard the phonograph record of White Christmas clearly and believed that the record was actually playing" while another 49% said "I heard the phonograph record of White Christmas clearly but knew there was no record actually playing."

So according to this experiment, over half of 1960s female students actually "heard" a record playing, simply because someone told them to. (In another part of the experiment, many of them "saw" a cat.) It's very hard to know what to make of this, because it's obvious that some of them may have just been saying that they heard the music because they thought this is what was expected of them. Bear in mind as well that the lead experimenter, Theodore Xenophon Barber, later became interested in some rather dubious stuff. Even so, the paper became popular, and led to a small industry of music-based hallucination research.

More modern work inspired by the White Christmas experiment has been a bit more rigorous. In 2001, two Dutch psychologists took 47 students and told them to listen to some white noise. The students were told that the song White Christmas might be played quietly at some points, and they should press a button whenever they heard it. 14 of them pressed the button at least once (on average, three times each), although the song was never actually played. This implies that a substantial number of healthy people will hear something simply because they expect to hear it, even if what they are actually listening to sounds nothing like it.

The lesson of all of this, if you need it spelled out, is that your eyes and ears are not windows through which you have direct access to reality. Your brain is actively constructing your perceptions of the world based on prior knowledge as well as sense data. But I feel like I'm getting dangerously close to talking philosophy here, so I'd better quit while I'm ahead.

[BPSDB]

The Hidden Face Within

One of these two images contains a hidden picture of a face. Which one?

This was the question faced by participants in a remarkable psychology experiment just published, Measuring Internal Representations from Behavioral and Brain Data.

Five healthy volunteers were presented with a series of random black and white grid patterns. Each grid square was either black or white, and this was randomly determined on each trial.

There was no pattern to the images, they were completely random. But the subjects were told that half of the patterns contained a hidden face, and that their job was to work out which ones did. Each subject saw over 10,000 random images and they took about 1 second to judge each one.


The volunteers "detected" a face in 44% of the images. Somehow, all five of them convinced themselves that they were seeing faces in many of the grids. The authors say that

Upon completion of the experiment we debriefed observers, and all expressed shock that no face was ever presented.

That's strange enough in itself, but here's the really clever bit. The authors compared the patterns which were declared to contain a face, to the ones that were reported as empty. The image below shows the average "face" grid, minus the average "non face" grid, for each individual subject:

As you can see, this reveals...a face! Kind of. The top half shows the raw average; the bottom half shows the statistically significant differences from random noise.

In Subjects 1 and 2, the face is pretty clear, with eyes, a nose and a mouth. For 3 and 4, it's less coherent, but you might be able to see it if you look hard enough. For Subject 5, not really.

What this means is that people (at least, most of them) were not just seeing faces in any noise. They tended to see faces when the random patterns happened to resemble a kind of primitive face, but it was a different face for each person. The authors say that these strange faces correspond to the individual's internal representations, or models, of "a face", that each subject was "seeing" in the noise.

Finally, the whole experiment was conducted while EEG data was being recorded from the participant's brains. The EEG results revealed that there was a clear difference in the neural activity associated with "face" compared to "nonface" stimuli - except in Subject 5, who you'll remember had the least coherent "internal face".

What's exciting about this approach is that it investigates perception in a purely "top down" way. Normally, when we look at anything, what we end up perceiving is a product of "bottom up" influences - the raw data - and "top down" ones - what we expect to see. In this experiment, there was no real "bottom up" data; it was all "top down".

This is a form of pareidolia - perceiving familiar things in random stimuli. Seeing the face of Jesus in your sock, that kind of thing. It works for sounds too: in the famous White Christmas Experiment, people report "hearing" music in pure white noise - when told to expect it. Real-life examples of this include the "Islam Is The Light" doll, and my personal favorite, the singing paedophile Christmas mouse.

Finally, I wonder what embodied cognition theorists make of this paper. Because this paper claims to be "Measuring Internal Representations from Behavioral and Brain Data"; embodied cognition (at least the radical kind) is the theory that "internal representations" either don't exist, or at least don't explain anything about human cognition.

Smith, M., Gosselin, F., and Schyns, P. (2012). Measuring Internal Representations from Behavioral and Brain Data Current Biology DOI: 10.1016/j.cub.2011.11.061