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01/31/2002 Archived Entry: "Confusion"

If you ever want to silence an experimental psychologist, ask them the question, "How do I reject candidates in the tip of the tongue state with only partial information?"

Actually, you could probably silence anyone by saying that, but not for the right reasons. So what does it all mean? Well, what I'm really talking about here is the issue of recalling memories. I'll start from the beginning. There used to be two schools of thought among psychologists about how we recalled memory.

The first school believed that we could remember data via an indirect method, using 'extra experimental information'. The second school believed that that was categorically not possible, and you could only remember data directly.

What do I mean? Let's imagine you are given the words 'time' and 'blue' and you have to remember them. Let's say that when the time comes, you can remember the word 'time' but you can't remember 'blue'. The experimenter takes pity on you, and says, "OK, I'm going to give you a clue. The clue is 'green'." Suddenly, you say, "Aha, yes, I remember now, the word is 'blue'."

What some people believe has happened here is that the 'retrieval cue' of 'green' sets off the node in your brain that represents 'green'. This node gets excited and sets off all the other nodes that it is connected to, in varying magnitudes according to the strength of its connections to them. So right then, the nodes for 'grass', 'red', 'peas' and 'blue' all get set off. All the nodes which are set off are examined for suitability to the present task, i.e. trying to remember what 'time' goes with, and 'blue' turns out to be the most suitable.

I've just described the indirect method of memory retrieval, indirect because you aren't retrieving the 'tbr' (to be remembered) item directly, you're retrieving something that is linked to it first.

Various studies were carried out on this by Bahrick (1970) and they were all very convincing and people said, yes, the brain must be able to perform indirect retrieval! But a guy called Tulving absolutely disagreed with this, which was quite daring since everyone was already convinced by Bahrick. Not that daring though, since Bahrick had some pretty fine experiments himself.

Let's say you're doing an experiment just like the first one I described, but you have to remember the two items 'dirty' and 'city'. Yet again, when the time comes, you can't remember either. To give you a clue, the experiment says, "Think of the word village - that's a clue." You rack your brains, and then you come up with 'city'. Well done.

But there are dozens of other people doing the test, and some of them still can't remember 'city' even when given the 'village' clue. In addition, another set of people who can't remember 'city' are asked to perform a free recall, in which they just say any words that they think could possibly be the one they're looking for. The results were surprising; the people who were given the 'village' clue did not perform significantly better than the people who weren't given any clues - the free recall people.

According to the indirect access model, that doesn't make any sense! They've just been giving a clue - a clue which is a cue, a retrieval cue, since theoretically the 'village' node should be connected to the 'city' node. So Tulving declared this to be the death of the indirect access model, and he made something called the Encoding Specificity Principle. In short, this principle stated that any clues you give people in trying to remember items will only be useful if those clues were given at the same time at which the to-be-remembered item was first remembered. So the clue of 'dirty' would work well, but only because you were exposed to it at the same time you were exposed to 'city'.

Tulving had another experiment which was just as convincing. People decided that indirect access just couldn't work.

A decade later, Jones (1982) made a classic experiment where he overturned the Encoding Specificity Principle. It was a very simple and elegant experiment. He gave subjects the following pairs of words to be remembered:

sleep - ORANGE
tide - NEWSPAPER

The first group were shown the words, and then they came back a bit later and were shown the words 'sleep' and 'tide' and were asked to remember the other words in the pair. If they couldn't remember, tough, they weren't getting any clues.

However, if members of the second group couldn't remember the other words, they were told by the experimenter, "Here's a clue. Look at the words 'sleep' and 'tide' and read them backwards." Ah, you see - they spell out 'peels' and 'edit'! Those crafty psychologists, eh? As you might expect, that clue allowed the second group to perform far better at recall than the first group.

Why does this overturn the Encoding Specificity Principle? Because the clues they were given were not given to them at the time of when they were presented the original information. The clues are what are called 'extra-experimental information'. As a result, the ESP was disproved, all of its followers were cast into confusion, everyone else was really happy, etc etc.

"But Adrian," I hear you cry, "this doesn't bring us any closer to the stuff you were babbling on about tongues and partial information!"

Ah, but it does (in a way). Imagine you're trying to complete a crossword, and you come across the clue, 'Lying on ones back, with the face upward.' You know the answer, it's just on the tip of your tongue, but you just can't get the word out. A friend comes along, looks at it, and says, 'Is it sleeping?' and you say, 'No, it's not sleeping'. He says, 'Does it begin with the letter T?' and you say, 'No, I know it definitely doesn't begin with the letter T.'

Hold on a second though! How on earth are you doing this? You don't know what the answer is, yet you still can somehow reject candidates for the answer? Well, I bet you'd like to know how it is that the brain can do this remarkable feat of having partial information about something and simultaneously know exactly what that something is not.

So would I - no-one has figured out the answer yet. And that, readers, is why I find experimental psychology and in particular, cognitive neuroscience, so interesting.

Incidentally, the answer to that crossword question is 'supine'.