Not Exactly Rocket Science covers an intriguing study that provides further evidence for the theory that the brain treats tools as temporary body parts.
Using tools has lots of interesting effects on our perception. In one of my favourite studies, psychologist Dennis Proffitt found that we perceive distances as shorter when we have a tool in our hand, but only when we intend to use it.
This latest study found that using a tool for only a few minutes modified the body’s action settings. In the experiment, participants were asked to repeatedly pick up a block that had been placed in the middle of the table.
Then, they had to repeat the same actions with a grabber – a long, mechanical lever tipped with a two-fingered “hand” – and then a third time, with their own hand again.
Small LEDs on the volunteers’ hands allowed Cardinali to track their movements and calculate the speed and acceleration of their arms. She found that they reached for the block differently after they had been accustomed to the grabber, taking longer to accelerate their hands more slowly and to seize the block (although once they actually touched the blocks, they grasped them in just the same way as before). The delays even affected the speed at which they pointed at the block, a behaviour that wasn’t “trained” by the grabber.
To Cardinali, these results suggested that after using the grabber, the volunteers’ had included it into their mental representation of their own arms. Because of that, they felt that their arms were longer than they actually were and reached for the block more slowly.
Link to Not Exactly Rocket Science on tools as body extensions.