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% C! o2 q* J4 E1 r8 C3 }2 o1 X "What this shows is that the capacity for how much we eat is driven by what we see, not necessarily by how much food is actually there," Wansink says. "Your stomach is a very imprecise instrument when it comes to measuring food—you might be able to tell roughly whether it's full or not, but you can't tell if it's full of meat or butter, calories or lettuce."
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Scheibehenne adds that vision has the advantage of immediacy, whereas our stomachs need more time to evaluate what we digest. Both Scheibehenne and Wansink also explain that over the course of our lives we build up a reliable visual memory that links different portion sizes to different levels of satiety. "We can think, 'Hey, I am usually full when I eat a full plate of food,'" Wansink says. "From 40 years of past experience, I know if I eat this I will probably be full—that's a much more reliable assessment than our stomachs give us."
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"I think it's a really clever design," Zald says. "They were able to simulate an eating situation quite well, and they measured quite a few different variables." The new study's design, however, presents two main potential confounding factors. First, the act of eating in the dark may have fundamentally changed the typical dining experience in more ways than the researchers intended. Most participants who dined blind reported at least some difficulty locating their food and using silverware, and—compared with diners who ate in the light—said that they paid much more attention to the taste of the unidentified food than to its weight or portion size.
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Second, participants who ate lunch in the well-lit restaurant were likely influenced by social cues that diners in the dark did not have. Participants with supersize portions in the light, for example, may have felt somewhat self-conscious about eating more than participants who had smaller portions, and may have subsequently resisted taking more fruit sticks than their peers. Scheibehenne says that he and his colleagues tried to control for this unintended peer pressure by having participants eat dessert with a different group of participants than they lunched with.! t2 M) c: Y5 d- Z% ]% c1 s
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Susan Roberts, a nutrition researcher at Tufts University School of Medicine, says she does not question the findings but thinks the unusual nature of the experiment should not be overlooked. "People were given food not really of their choice in complete darkness—it's just not relevant to normal eating at night," Roberts says. Moreover, the study group itself, in which 74 of the 96 participants were university students, may not be a good sample, she suggests. "College students and free food are not a great combination."1 i& a7 Y i P% e7 |% x5 d
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Nevertheless, Scheibehenne feels the study offers general lessons. "It's important to pay attention to things in the environment that could trick you into thinking a particular portion size is smaller or larger than it really is, or distort your visual cues," he points out. Consider how eating in front of the television keeps our eyes on a screen instead of on our plates, for instance.
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Wansink echoes this concern: "When your food is out of sight, it's out of mind. And this doesn't just happen in a dark restaurant. If you serve yourself small portions deliberately, you could be in tremendous danger of repeatedly refilling your plate and overeating." |