When posing for portraits, humans favour the left cheek. This preference is argued to stem from the left cheek’s greater expressivity: as the left hemiface is predominantly controlled by the emotion-dominant right hemisphere, it expresses emotion more intensely than the right hemiface. Whether this left cheek bias extends to our closest primate relatives, chimpanzees, has yet to be determined. Given that humans and chimpanzees share the same oro-facial musculature and contralateral cortical innervation of the face, it appears probable that humans would also choose to depict chimps showing the more emotional left cheek. This paper thus examined portrait biases in images of chimpanzees. Two thousand photographs were sourced from Instagram’s “Most Recent” feed using the #chimpanzee, and coded for pose orientation (left, right) and portrait type (head and torso, full body). As anticipated, there were significantly more left cheek (57.2%) than right cheek images (42.8%), with the bias observed across both head and torso and full body portraits. Thus humans choose to depict chimpanzees just as we depict ourselves: offering the left cheek. As such, these data confirm that the left cheek bias is observed in both human and non-human primates, consistent with an emotion-based account of the orientation preference.

当摆姿势肖像时，人类偏爱左脸颊。认为这种偏爱源于左脸颊更高的表现力：由于左半脸主要受情感主导的右半球控制，因此它比右半脸更能强烈地表达情感。这种左颊偏向是否延伸到我们最接近的灵长类近亲，即黑猩猩，尚待确定。鉴于人类和黑猩猩拥有相同的面部表情和对侧皮质神经支配，因此人类似乎也有可能选择描绘黑猩猩，表现出更多的左脸情感。因此，本文研究了黑猩猩图像中的肖像偏差。使用＃黑猩猩从Instagram的“最新” Feed中获取了两千张照片，并对姿势定向进行了编码（左，右）和肖像类型（头部和躯干，全身）。正如预期的那样，左脸颊图像（57.2％）比右脸颊图像（42.8％）明显多，并且在头部和躯干以及全身肖像上均观察到偏见。因此，人类选择描绘黑猩猩的方式就像我们描绘自己的方式：提供左脸颊。这样，这些数据证实在人和非人的灵长类动物中都观察到左颊偏斜，这与基于情感的取向偏好说明相一致。