Hack67.Objects Ask to Be Used
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Hack 67. Objects Ask to Be Used
When we see objects, they automatically trigger the movements we'd make to use them. How do we understand and act upon objects around us? We might perceive the shape and colors of a cup of coffee, recognize what it is, and then decide that the most appropriate movement would be to lift it by the handle toward our mouth. However, there seems to be something rather more direct and automatic going on. In the 1960s, James Gibson developed the idea of object affordances. Objects appear to be associated with (or afford) a particular action or actions, and the mere sight of such an object is sufficient to trigger that movement in our mind. There are obvious advantages to such a system: it could allow us to respond quickly and appropriately to objects around us, without having to go to the bother of consciously recognizing (or thinking about) them. In other words, there is a direct link between perceiving an object and acting upon it. I don't just see my cup of coffee; it also demands to be picked up and drunk. 6.7.1. In ActionYou may not believe me yet, but I'm sure you can think of a time when your movements appeared to be automatically captured by something in your environment. Have you ever seen a door handle with a "Push" sign clearly displayed above it, yet found yourself automatically pulling the door toward you? The shape of the pullable handle suggests that you should pull it, despite the contradictory instruction to push it. I go through such a door several times a week and still find myself making that same mistake! Try finding such a door near where you live or work. Sit down and watch how people interact with it. What happens if you cover up the "Push" sign with a blank piece of paper? Or cover it with a piece of paper labeled "Pull"; does this appear to affect how often people pull rather than push, or is the shape of the handle all they're really paying attention to? Perhaps you've found yourself picking up a cup or glass from the table in front of you, even though you didn't mean to (or even knowing that it belonged to someone else)? Effects of object affordances have been found in experiments: Tucker and Ellis1 asked subjects to press a button with their left or right hand, to indicate whether a picture of an object was the right way up or inverted. Even though subjects were not thinking about the action they would use for that object, it had an effect. If they saw a cup with a handle pointing toward the rightevoking a right-hand graspthey were faster to react if their response also happened to require a right-hand response. That is, the reaction time improved if the hand used for the button press coincided with the hand that would be used for interacting with the object. This is called a compatibility effect. (The Simon Effect [Hack #56] shows that reaction times improve when stimuli and response match in the more general case. What's happening here is that the stimulus includes not just what you perceive directly, but what affordances you can perceive too.) The graspability of objects can affect judgments, even when people are not making any kind of movement. de'Sperati and Stucchi2 asked people to judge which way a moving screwdriver was rotating on a computer screen. People were slower to make a judgment if the handle were in a position that would involve an awkward grasping movement with their dominant hand. That is, although they had no intention to move, their own movement system was affecting their perceptual judgment. 6.7.2. How It WorksBrain imaging has helped us to understand what is happening when we see action-relevant objects. Grèzes and Decety3 looked at which brain areas are active when people do the Tucker and Ellis judgment task. Bits of their brain become active, like the supplementary motor area and the cerebellum, which are also involved in making real movements. In related research in monkeys, cells have also been discovered that respond both when the monkey sees a particular object and also when it observes the type of action that object would require. People with damage to their frontal lobes sometimes have problems suppressing the tendency to act upon objects. They might automatically pick up a cup or a pair of glasses, without actually wishing to do so (or even when they're told not to). It is thought that we all share these same tendencies, but with our intact frontal lobes, we are better at stopping ourselves from acting them out. (Frontal patients can also have trouble suppressing other impulses; for instance, some become compulsive gamblers.) So, objects can produce movements within our mind, but just how do they do so? We don't know the answer to this yet. One possibility is that these effects happen automatically, as Gibson suggested. Our system for visual perception has two routes [Hack #66] : the ventral (or "what?") route, concerned with the identity of the object and the dorsal ("where?" or "how?") route, concerned with location and action. Affordances may act directly on the dorsal stream, without relying on any higher processing; information about the type of movement might be extracted directly from the shape or location of the object. However, our knowledge about objects must play a role. We certainly couldn't have evolved to respond to everyday objects of todayprehistoric man didn't live in a world filled with door handles and coffee mugs! These automatic responses must be learned through experience. Recently, Tucker and Ellis4 found that merely seeing an object's name was enough to speed reaction times to produce the relevant size of grasp. Thus, our previous experience and knowledge about acting upon objects become bound up with the way that we represent each object in our brains. So, whenever you see (or simply consider) an object, the possibility of what you might do with it is automatically triggered in your mind.
6.7.3. End Notes
Ellen Poliakoff |
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EAN: N/A
Pages: 159