The study found that subjects showed different physical responses to loud noises when they were being paid to keep track of tones that were interrupted by those noises, says author Larry W. Hawk Jr., Ph.D., of the State University of New York at Buffalo, writing in the September issue of the journal Psychophysiology.
The researchers recruited 43 college students, all of whom received college credit in exchange for participating in the study. But one group of 22 students received up to $5 each, depending on how well they performed on a task, while the other group of 21 students was simply told, "For the information that we collect from you to be useful, it's crucial that you try your best."
Each participant was put into a soundproof booth and given headphones. Electrodes measured the size and strength of each subject's blinks as a response to a loud noise, giving an indication of how closely the student was paying attention. The subjects then listened to a series of tones and were asked to count the number of longer-than-usual tones that were played in a particular pitch, while ignoring tones in a different pitch.
On average, the authors found, paid volunteers were more attentive to the sounds, as measured by their decreased blink size and strength, compared to the unpaid volunteers, indicating that motivational factors can influence attentiveness. The authors add that not only did the paid subjects pay more attention to the tones when compared to the unpaid subjects, but they also did better at ignoring the sounds they were supposed to ignore.
Although the paid group showed more physical evidence of paying attention, they did not perform significantly better than their unpaid counterparts. Overall, task performance was generally good, with 60 percent of participants either reporting the exact number of longer-than-usual attended tones, or being off by only one from the correct answer.
Although the researchers used the external incentive of money for their study, other research has shown that just making the task at hand interesting can be an incentive. For example, one study showed that subjects who were assigned a continuous task performed well even though they were not paid.
"The motivation for [paying more attention] may be due to inherently interesting stimuli or to an [external] incentive for strong task performance," the researchers say.
Hawk adds, "This task provides a way to study how emotion and attention interact, whereas most research has focused on one or the other."
The researchers note that children with attention-deficit hyperactivity disorder do not show the same decreased blink size and strength during tasks compared with a control group of children, but suggest further study on the effect of incentives in that population.
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