单选题 Since the 1930s, the idea that creatures might advertise their " fitness " as mates through symmetry has been around. It rests on the notion that factors ranging from bad genes to coming off worse in too many fights will lead to asymmetries others can see. And over the past few years, experiments with animals and humans seemed to support the idea that symmetry in features such as plumage and facial characteristics influences mate selection.
But no one had actually checked that the animals in these experiments can actually see the subtle differences in symmetry, typically of between 1 and 2 percent. Now the first such experiment has been carried out. The results are worrying for advocates of symmetry detection as a powerful factor in mate selection.
John Swaddle, an ethnologist at the University of Bristol, performed the experiment using wild starlings, which have excellent eyesight. He trained them to hit keys marked with bar patterns with varying levels of asymmetry in order to receive food rewards. This showed the starlings could easily detect asymmetries of between 5 and 10 percent. But at between 1 and 2 percent, their performance plummeted to no better than random guessing.
" This suggests that the levels of asymmetry that birds encounter in nature will often be just too small to be detected, " says Swaddle. He says experiments that linked small asymmetries to fitness may have produced misleading correlations, and says the only direct evidence that birds use asymmetry as a cue to mate fitness involves levels of asymmetry of at least 10 percent. " I think signaling by asymmetry will probably only occur when species show such very large asymmetries—and this doesn't occur that often. "
This raises questions about research suggesting that humans are influenced by visual asymmetry in their choice of partner. Michael Butt of the Perception Laboratory at the University of St. Andrews, who has carried out such experiments, concedes that no one has ever checked if humans have a threshold to asymmetry detection. He thinks a conclusive test of this would probably involve manipulating complex three-dimensional images: " It would be a very difficult experiment to do "
Burt adds that the abilities of animals to detect asymmetry in bar patterns may not reflect their talent for spotting asymmetries in body shape. " The visibility of an asymmetry may well depend on its type, " he says. Swaddle agrees, and is planning further experiments. " But I suspect that asymmetry is used as a visual cue less often than most people appear to presume, " he warns.

单选题 Most people often presume that in mate selections creatures appeal to______.

【正确答案】 D

【答案解析】[解析] 细节题。根据第一段第一句“Since the 1930s, the idea that creatures might advertise their ' fitness' as mates through symmetry has been around. ” (自从20世纪30年代起，这样一种观点开始盛行，即认为生物借助对称性来展示他们充当配偶的适合性。)及末段末句“…asymmetry is used as a visual cue less often than most people appear to presume”(非对称性真如许多人想象的那样经常被作为一种可视信号吗?对此我持怀疑态度。)可知，很多人认为对称性是是否适合作为配偶的重要信号。因此D项正确。文章首句告诉我们生物借助对称性来展示他们充当配偶的适合性，可知适合性是生物择偶时的标准，而考量适合性需要参考客观指标，不能说参考适合性来考量适合性，故A项不合逻辑；根据文章首句，有人认为对称性是适合充当配偶的信号，而不是非对称性，故排除B项；首段末句提到面部特征的对称性只是对称性的一种，C项以偏概全，故也可排除。

单选题 According to the passage, which of the following is TRUE?

【正确答案】 D

【答案解析】[解析] 是非判断题。第五段第二句提到“…no one has ever checked if humans have a threshold to asymmetry detection.”(没有人检验过人类是否能感知非对称性)，因此D项正确。第四段第二句提到“He says experiments that linked small asymmetries to fitness may have produced misleading correlations…”(他说那些将细微的非对称性与生物择偶时考虑的适合性联系起来的实验会让人们误以为两者具有相关性)，因此不能笼统地说非对称性与配偶适合性有关联，故排除A项；末段第二句提到“The visibility of an asymmetry may well depend on its type”(非对称性的可视度也许取决于它的类型)，也就是说不能脱离具体的非对称类型谈论其是否可视，例如文中的欧掠鸟对一定比例以下的非对称性便无法感知，故排除B项；第四段末句提到“I think signaling by asymmetry will probably only occur when species show such very large asymmetries—and this doesn't occur that often.”(我认为只有当物种显示出非常大的非对称性时，非对称性才能被作为配偶选择时的信号，但是这种情况很少发生。)，也就是说非对称性如果没有达到足够大的程度，是无法被当作择偶信号的，故C项的说法过于绝对。

单选题 John Swaddle's experiment suggests that______.

【正确答案】 A

【答案解析】[解析] 推理题。第四段最后一句提到：“I think signaling…and this doesn't occur that often.”(我认为只有当物种显示出非常大的非对称性时，非对称性才会成为配偶选择时的信号，但是这种情况很少发生)所以A项正确。第四段第二句提到“experiments that linked small asymmetries to fitness may have produced misleading correlations”(那些将细微的非对称性与生物择偶时考虑的适合性联系起来的实验让人们误以为两者间具有相关性)，B项是对此的曲解；John Swaddle的实验只是考察了鸟类对非对称性有多大的感知能力，没有讨论鸟类在择偶时是否依赖对称性，故排除C项；文章提到“对于只有1%到2%之间的非对称性，欧掠鸟的判断力则急剧下降到近乎随意乱猜”，这只是对感知很小的非对称性而言的，不能笼统地说随意乱猜的效果与感知非对称性的效果一样，故排除D项。

单选题 According to the text, in mate selection human beings______.

【正确答案】 D

【答案解析】[解析] 细节题、第五段最后两句提到“…no one has ever checked if humans have a threshold to asymmetry detection…It would be a very difficult experiment to do”(…没有人检验过人类是否能感知非对称性。…这个实验很难做)，可知D项正确。根据第五段第二句，没有人检验过人类是否能感知非对称性，自然无法知道人们择偶时是否会考察对称性，故排除A项；第五段末句提到“a conclusive test of this would probably involve manipulating complex three-dimensional images…”(能够检验这个问题的结论性的实验也许需要处理复杂的三维图像)，但这并不是说人类选择配偶时需要关注三维图像，故排除B项；C项内容文中并未提及。