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Experience psychology - Prism adaptation experiment

For school students vising the department we run a two hour session investigating adapting to a visual shift. This was first explored by George Stratton in the 90's (the 1890s!) and by Ivan Kohler in the 1950's using inverting glasses, and more recently seen on the BBC TV series Human Senses (2003).

The Experience psychology programme is coordinated by Peter Thompson and Rob Stone.

The experiment

Students 'playing' to get experience

In this experiment subjects first record their hand-eye co-ordination by trying to point (with their eyes closed) at a previously seen line. We then give the subjects a pair of rather fetching glasses which shift the world 15 degrees to the left and they repeat the task, usually with dramatic errors. [prisms-instructions (PDF , 198kb)

The subjects then adapt to this new visual world. Initially very disorienting after a 30 minute adaptation phase (involving lots of hands on games and interaction) they start to improve stumble less and score more points in their games. 

Within as short a period as half an hour most of the subjects have become used to their new world and they perform the tasks with increasing accuracy. We then repeat the measurements to see how their experiences have changed their pointing abilities. Even after only a short time they have improved markedly, showing they have adapted to their new world.

Removing the glasses

Students in wheelchair

On removing the glasses the subjects experience a very strange phenomenon when repeating the task for a final time, when they dramatically and reliably fail to hit the target.

But what if instead of practicing all the games to aid re-calibration the subject just wears the glasses and sees the world without really exploring or experiencing the change, would the adaptation occur to the same extent?

To test this idea one of our subjects is pushed about in a wheelchair with their hands and feet hidden from view. They get the same visual information that the other subjects but no interaction.

Typically we find that the performance is not much improved over the 30 minute period. Consequently when they remove the glasses and try the task again they have very small errors, showing that really they haven't adapted to their new world at all well.

This experiment is housed within the Psychology building, with the students as subjects and experimenters, looking at the data and simple comparison of the means and distributions of the scores.

We hope they enjoy the session which demonstrates that Psychology is not about analysing people but rather about designing and running experiments to investigate human behaviour.


If you've enjoyed this and want to know a bit more about psychology there are plenty of books, here are a few of the better introductions: