Change Blindness

Change Blindness is an interesting psychological phenomenon that’s attracting a lot of research these days. There are a number of theories about why it occurs, and from a quick look at the literature I’m inclined to think it’s something to do with the role of attention and something called re-entrant processing.

Armchairs and onions

One of the great things about being in UCSD right now is that I get to go to any classes I want, free of charge (unlike the poor saps who have to pay hundreds of bucks for the privilege – of course, they need course credit…). So at one of the recent cognitive neuroscience classes I went to (they’re really lectures), a guest speaker was there – a philosopher-turned-neuropsychologist.

During his lecture, one of the most amazing things happened. I didn’t fall asleep. Granted, I did doze off for a few seconds during the previous speaker’s lecture, but even so. Anyway, this ex-philosopher was talking about that old chestnut, the mind body problem, and also of course qualia.

I was expecting that I wouldn’t hear anything that was particularly new to me, since this was essentially an introductory one hour lecture and I’ve read a few books by people like Dennett that cover the same sort of material. Luckily, I was wrong. The first thing that caught my attention was the speaker’s listing of two conceptions of philosophers, the armchair conception and the onion conception.

The armchair conception is what we traditionally think of philosophers as; people who seek to answer questions a priori, that is, without experience of the matters in question. This means that, surprisingly enough, they can do everything from their armchairs. Scientists on the other hand act a posteriori, by conducting experiments and looking at the world.

The problem with this, the speaker argued, is that many philosophers such as Aristotle and William James defied the armchair classification because they did conduct experiments. Aristotle, for example, had a great interest in biology and went around dissecting things to find out more about them. So to accommodate this, there’s the onion conception. In this, the area of knowledge and questions that philosophers address is continually shrinking inwards, and as it shrinks, the layers it sheds become new disciplines that are more capable of addressing those questions that philosophy alone cannot. One of the first layers to be shed would be mathematics, and then subsequently disciplines such as biology, physics and so on.

One of the latest disciplines to be shed is psychology, which didn’t even exist separately until around one hundred and fifty years ago. Psychology and the now related area of neuroscience are now thus capable of better investigating the nature of the mind body problem, qualia, consciousness and all the rest.

Another great thing about being in UCSD is seeing the heavyweights of psychology and neuroscience plan their strategies and arguments. A couple of days ago I was having coffee with Prof. Ramachandran and a few others, and we were discussing how to pin down Damasio’s somatic marker theory, which is a hot topic in psychology and is regularly taught in psychology courses across the world. It struck me then, that, wow, this is how and where science gets made.


People might be wondering what it is that I’m doing in San Diego, beyond my rather nebulous description of ‘research’. Right now I’m working in the research labs of V. S. Ramachandran at the University of California, San Diego Center for Human Information Processing on an experiment to investigate an interesting condition called synaesthesia. Synaesthesia is basically what happens when your senses get mixed up and interconnected in strange ways. For example, when some synaesthetes read letters or digits, they’ll see them coloured (even when they don’t originally have colours). Others will associate sounds, music, shapes or even people with colours or smells. Essentially, any combination of the senses is possible, although grapheme-colour synaesthesia (a grapheme is a character) is the most common.

Estimates of the prevalence of synaesthesia vary from 1 in 200 to 1 in 20,000. The people in the lab I’m working at tend towards the former number. If that’s the case, chances are that you know someone personally who has synaesthesia – the only problem is that synaesthetes are either embarrassed about talking about their experiences, or they simply think that everyone is like them. One day the graduate student I’m working with was talking to a friend about a synaesthete who, when listening to speech, would see the words scroll along the bottom field of his vision, like subtitles. The friend said, “But doesn’t everyone have that?”

It’s generally thought that synaesthesia has a significant genetic component, and because it tends to be passed along the female line, it probably resides in the X chromosome. For a long time it was believed this couldn’t be true because Vladimir Nabokov had synaesthesia and so did his son Dmitri – so this meant that it couldn’t be in the X chromosome (sons inherit only the Y chromosome from their fathers). Of course, it turned out that Nabokov’s wife was also a synaesthete.

Why is synaethesia a big deal all of a sudden? Synaesthesia was ignored for a long time by psychologists due to the long-lasting age of behaviourism (‘don’t listen to what the subject says, just measure him’), and in any case many people simply thought synaesthetes were speaking metaphorically, e.g. “This cheese has a pretty sharp taste.” A series of pioneering experiments conducted over the last ten and twenty years have completely reversed this, showing that not only is synaesthesia a genuine phenomenon, but it’s also a perceptual one. By this, I mean that synaesthetes really see (say) colours when they see numbers. It’s not that they have an eidetic memory and can learn the sensory associations, they really experience them.

This has resulted in some interesting findings. Synaesthetes appear to have superior memory, and their ability to associate senses makes for good artists and writers. One of the things we’ll be doing in the lab is to talk to a trilingual synaesthete who experiences colours when she hears words – will the same word in the different languages elicit the same colour? Or will the phonological properties of the word – the sound of the word – matter more than the semantic meaning?

The point behind all of this is not merely to have a look at an interesting new condition. Synaesthesia also promises to shed light on some of the more profound questions about attention, perception, information processing in the brain, and consciousness. As such, it’s a very ‘sexy’ new topic and researchers are flocking towards it. It’s already been featured in a computer game, Rez (which is also very fun) and the other day I saw a mention of it in a Stephen Baxter SF novel. The main thing I’m working on here is a metacontrast experiment that’s aiming to find out exactly when the experience of colour occurs in the processing of visual information in synaesthetes. It’s a useful experience for me, especially given that many key findings about synaesthesia were made by people in the lab I’m in now.


Quote of the day: “The thing with behaviour is that we don’t know what subjects are thinking. I don’t know whether my rats are pressing the lever because they know they’ll get heroin – and I don’t know whether children will be surprised because they think ‘Hey, the laws of gravity have changed!'”


I got an email today from my psychology supervisor, Prof. Simon Baron-Cohen (the autistics guy) who said that unfortunately he wouldn’t be able to give us an extra supervision for the exams since he’s flying out to Kosovo to help with their new child psychiatry service. I think that is impossibly neat.

Garden path

There’s an interesting phenomenon in language comprehension called the ‘garden path effect’. Proposed by Frazier and Fodor (1979), it basically meant that when you are reading or hearing a sentence, you split it up into chunks (you parse it), and due to something called ‘late closure’ you keep on adding as many words as possible to the current chunk you’re working on. This works quite well to illustrate the way in which we comprehend language.

Take a look at these examples:

1. (Since Jay always jogs a mile) he is very fit.
2. (Since Jay always jogs a mile) seems like a short distance.
3. (Since Jay always jogs) a mile seems like a short distance.

In (1), keeping the chunk as long as possible works quite nicely. In (2), it fails miserably since if you use the chunk illustrated there, the sentence doesn’t make any sense. Instead, you’d have to backtrack and reposition your chunk as shown in (3). Now, this all sounds a bit woolly until you realise that there’s plenty of evidence for this from latency measurements and eye movement studies. The latter in particular are neat – you can see people reading a sentence, come to a screeching halt as the garden path model fails them and then regress to the nearest noun.

There’s another possible method of parsing sentences, and that’s by looking at its semantics – its meaning – and parsing the sentence in a way that makes the most sense.

1. (The defendent examined) by the lawyer turned out to be unreliable.
2. (The evidence examined) by the lawyer turned out to be unreliable.

In (1), there are two possible places to position the first chunk. The defendent could be doing the examining (wrong, as shown above) or the defendent could be the one being examined (right, not shown). In (2), there’s only one meaning – since evidence can’t do any examining (it’s not alive, is it?), it must be being examined. So according to semantic parsing, you’d expect that people would have fewer problems reading (2) than (1). And that’s true, according to eye fixation studies. By the way, in both the sentences above, the parsing has been done ‘wrong’ – it has been done according to the garden path model with late closure.

As usual in these things, the two models (semantic and garden path) have been put together in a new ‘connectionist’ approach which takes the best bits from both. But that’s not what I’m interested in. What I’m interested in are the implications of altering the meanings of a word. Imagine if you had this sentence:

The AI examined by the lawyer turned out to be unreliable.

Now, imagine we go back far enough such that it is inconceivable that AIs are intelligent enough to do any examining. This would mean that there is only one way to parse the first chunk, as the AI is being examined. But go forward x decades to when it is conceivable that AIs could be examining something – you’ve just created an alternative parsing structure for the sentence. How does the brain cope with this? Is there a gradual alteration of the semantic structure and do the effects of this slowly filter down the language systems, or is the change sudden?.

(I just realised that I may have misunderstood the exact mechanisms of parsing and where to put the brackets, but the general concepts still hold. I think I’m right, anyway…)


While I have some issues with neurobiology lectures, I definitely don’t with our supervisions. They’re usually a great mixture of brainstorming and learning of interesting facts.

Take, for example, today, when I learned that when cats are hostile to each other and their hair stands on end, it’s because their hair makes them look much bigger than they really are.

Also, our supervision posed the interesting question – if squirrels didn’t have to forage and store hundreds or thousands of nuts over the winter and instead could get them from the supermarket, as we do, how would that impact on how closely their functions of consummation and apetite were entwined?

And why do foxes, when entering a barnhouse full of hens, kill every single one but only take one (or none!) off with them to eat?

Neuro and Psych

There were two things that caught my attention today in lectures. The first was a list of symptoms of mania (an abnormal emotional state, the opposite of depression):

i. Unfounded elation
ii. Hyperactivity
iii. Talkativeness and “flight of ideas”
iv. Distractivility
v. Impractical, grandiose plans
vi. Inflated self-esteem
vii. Reduced sleep

…and I thought, ‘I wonder if I know anyone who has those symptoms…’

The other thing that caught my eye was this passage from a lecture handout:

If the brain was organised logically and economically, then the neural systems responsible for the control and initiation of writing should be located close to the primary langauge systems. Therefore hand dominance (left or right handedness) and language laterality (whether your language centres are located in your brain’s right or left hemisphere) should eb tightly correlated, with the dominant hand being contralateral to the language dominant hemisphere.

If you got all of that, good. But I have some real problems with that passage. Firstly, we only started writing a few thousand years ago, and indeed literacy only became widely prevalent in the last couple of millenia, so frankly writing could not have had any realistic impact on human evolution. Note that I’m only talking about writing, I’m not talking about hand dominance (e.g. which hand you throw with, which hand you use for complex tasks) which incidentally would make much more sense.

Secondly, what’s all this talk about the brain being organised logically and economically? Evolution is a powerful thing, to be sure, but it’s not perfect and it’s entirely possible that there are many good reasons why the language systems would not have to be next to the writing (or dominant hand control) centres. In fact, as far as I can tell, there are only two reasons for why people believe this. The first is that there is a significant correlation between language system lateralisation and dominant hand control lateralisation.

The second is that some people thing, ‘Well, language is a complex task and so is hand control. They both need lots of processing power, so obviously they should be put in the same place.’ This argument is so terrible that I need not discuss it further.

Anyway, I suspect that all of this is down to the lecture handout being rushed, but I do wonder if lecturers realise that making even the smallest typo or factual error in their handouts can cause unlimited amounts of grief to all revising students.