I’m sure most Cognitive Daily readers are aware of the massive debate permeating the scientific world these days. No, not evolution versus creationism; I’m talking about object- versus space-based attention.
Haven’t heard of this raging debate? Well, then, let me refer you to a fascinating pair of experiments conducted by Massimo Turatto, Veronica Mazza, and Carlo UmiltÓ. The issue comes down to this: a critical problem for psychologists is the issue of attention. How does the perceptual system decide where to focus our attention when literally millions of bits of information are available to us at a given time? The object-based school believed that attention was focused on objects: when we notice a change to one part of an object, we’re more attentive to other changes in that object (e.g. when the car in front of us puts its turn signal on, we’re more likely to notice it slowing down for a turn). The space-based school believed that attention was focused on particular regions: we’re more likely to notice a change near where we’ve seen another change, whether or not the changes occur on the same object (e.g. if we see the neighbor’s dog running across their backyard, we’re more likely to notice the squirrel she’s chasing).
But the attention problem isn’t limited to things we see. Our sense of hearing, touch, and even smell can inform what we pay attention to — for example, the turn of the key in the door alerting us to a loved one’s arrival. Turatto’s team realized that by focusing on hearing, they could address the object versus space debate.
They set up an apparatus to combine visual and auditory inputs at the same time: a large black cardboard box concealing four loudspeakers, all in a dark room. The speakers were arranged in a square 90 centimeters on a side. In front of each speaker were three LEDs: red, green, and orange. Participants sat in looking toward the loudspeakers and were told that their task was to respond as quickly as possible when they saw a red or green LED flash, pressing the B key on a computer keyboard when they saw a red light, or the N key when they saw a green light.
During the experiment, the two speakers on the right emitted an intermittent high-pitched sound, and the speakers on the left produced a lower pitch of the same sound (I’ve approximated how this sounds here). At a predetermined time (the 7th repetition of the low-pitched sound), an orange LED flashed in front of one of the two speakers used to play that sound. Then, synchronized with the ninth repetition of one of the two sounds, either a red or a green LED flashed, signaling participants to press the corresponding button on the keyboard. Here are the results:
As you might expect, the fastest reaction times occured when the red or green LED flashed at the same spot, with the same sound where the orange LED flashed. The second fastest reaction was when the LED flashed with the same sound, but in a different spot. The slowest reactions occcured when neither the sound nor the spot was the same.
So how does this result impact the raging debate about object- versus space-based attention? If attention were only space-based, then only the when the red or green LED flashed in the same spot where the orange LED had appeared would reaction times be faster. Turatto et al. argue that the different tones constitute “sound objects,” analogous to physical objects you can see. Thus, their experiment supports the idea of object-based attention. But the team also believed space-based attention had some merit. To support this argument, they conducted a second experiment, where identical tones were played from each speaker — but still alternating from left to right, as before. Here are the results of that experiment:
Now only when the orange and red or green LEDs flashed in exactly the same spot did faster reaction times occur. Since the sounds coming from the speakers on the left and right were the same, they did not constitute separate sound objects for listeners, so instead participants attended only to the location of the LEDs. Thus, support for both object- and space-based attention was found in an elegant pair of experiments.
So the next time some object-based attention zealot claims that only object-based or space-based attention should be taught in the schools, you now have the knowledge to retort that both object and space-based attention have merit. Can’t we all just get along?
Turatto, M., Mazza, V., & UmiltÓ, C. (2005). Crossmodal object-based attention: Auditory objects affect visual processing. Cognition, 96, B55-B64.