Psychology research is not generally very good at capturing change. Measurements tend to be fairly static, either looking at one slice of time or asking participants to average over a period. Which is why this research on smiling is so unusual. Some of the best known research on smiling is about how people judge an authentic smile - the so-called 'Duchenne smile' or the 'crinkly-eyed smile'. What this research asks, though, is how does a smile's speed in combination with head-tilt and gender affect its perception.

In this experiment, one hundred participants, half men half women, were sat in front of a monitor to judge the smiles of synthetic faces (Krumhuber, Manstead & Kappas, 2007). They watched the faces smiling - some whose smile appeared in just over 0.1 of a second, and some whose smile appeared in just over 0.5 of a second. At the same time, some of the heads were tilted to the left and some to the right. Participants then had to judge the smiles on how trustworthy, attractive, dominant, fake and flirtatious they made the faces seem.

Results

The study replicated a previous finding that a long-onset smile (0.5s onset) is seen as more authentic and flirtatious. On top of this, the researchers found long-onset smiles were perceived as more attractive, more trustworthy and less dominant. Head tilting also increased attractiveness and trustworthiness but only if the head was tilted in the right direction. In this case, the right direction was the same way as eye orientation or towards a partner.

Gender

There was also evidence that smiles are perceived in different ways depending on the gender of both the target and the observer. Previous research has found that smiling is associated with attractiveness in women, but dominance in men. These are probably a result of gender stereotypes. One finding in the present study was that women's smiles were judged less authentic than men's. Krumhuber et al. (2007) speculate that this is because women tend to smile more than men, so their behaviour is seen as more usual and therefore less informative. The reverse may be true for men.

While women's smile were more likely to be discounted, it seemed women were generally better at detecting the difference between short- and long-onset smiles. The differences found in this study, therefore, were mostly due to female participants rather than the men. Krumhuber et al. (2007) suggest this ties in with findings men are more likely to interpret ambiguous or inauthentic signals (short-onset smiles) as flirtatious behaviour. They can't (or won't) tell the difference.

心理学研究在与时俱进上做得不太好，测量变得一成不变，要么随便瞄一眼（结果）要么问问被试（结果）平均一下啊整合成一个模型。这也是为什么这项对微笑的研究如此不同寻常。一些最知名的对微笑的研究都是关于人们怎么辨认一个真诚的微笑-又称杜乡的微笑①或鱼尾纹微笑。而这项研究是一个微笑的速度、头部倾斜还有性别是怎样综合影响微笑的效果的。

在实验中，一百名被试男女各占一半，坐在一个显示器前来辨认一些人工合成的笑脸 (Krumhuber, Manstead & Kappas, 2007)。他们观看的脸上出现的微笑有的只持续0.1秒，有的持续0.5秒。与此同时，一些头部在微笑时左倾，一些右倾。然后被试将判断他们看过的笑脸有多大程度的真实、有吸引力、张扬、虚伪和调情。

结论

研究验证了之前的发现，一个长时间的微笑（持续0.5秒）看起来更真诚和引人遐想。研究人员进一步发现了长时间微笑显得更有吸引力、更真诚而不那么张扬。头部微倾同样会增加吸引力和可信度但只限于右倾。在这里右倾指的是你面向对方时的右边。

性别

也有证据显示观看者和微笑者的性别对结果都有影响。以往的研究发现在女人看来微笑是和吸引力联系在一起的，但对男人这种联系更明显。这可能与成见有关。最近的一项发现是女人比男人更常微笑，所以她们的这一行为就更普通而因此削弱了信息性。反过来对男人也适用。

虽然女人的微笑更容易被忽略，但女人在辨别长、短微笑的区别上做的要比男人好。这项发现的原因可能是由于女性被试在测试中更专注。Krumhuber et al. (2007)认为这项发现意味着男人更容易把模棱两可或者不真实的信号（短持续微笑）当成调情行为。他们不能（或不愿）发现区别。