Supplementary data for the paper: Replicating five pupillometry studies of Eckhard Hess

Several papers by Eckhard Hess from the 1960s and 1970s report that the pupils dilate or constrict according to the interest value, arousing content, or mental demands of visual stimuli. However, Hess mostly used small sample sizes and undocumented luminance control. In a first experiment (<i>N</i> = 182) and a second preregistered experiment (<i>N</i> = 147), we replicated five studies of Hess using modern equipment. Our experiments (1) did not support the hypothesis of gender differences in pupil diameter change with respect to baseline (PC) when viewing stimuli of different interest value, (2) showed that solving more difficult multiplications yields a larger PC in the seconds before providing an answer and a larger maximum PC, but a smaller PC at a fixed time after the onset of the multiplication, (3) did not support the hypothesis that participants’ PC mimics the pupil diameter in a pair of schematic eyes but not in single-eyed or three-eyed stimuli, (4) did not support the hypothesis of gender differences in PC when watching a video of a male trying to escape a mob, and (5) supported the hypothesis that arousing words yield a higher PC than non-arousing words. Although we did not observe consistent gender differences in PC, supplementary analyses showed gender differences in eye movements towards erogenous zones. Furthermore, PC strongly correlated with the luminance of the locations where participants looked. Overall, our replications confirm Hess’s findings that pupils dilate in response to mental demands and stimuli of an arousing nature. Hess’s hypotheses regarding pupil mimicry and gender differences in pupil dilation did not replicate.

埃克哈特·赫斯（Eckhard Hess）在20世纪60至70年代发表的多篇论文指出，瞳孔会根据视觉刺激的兴趣价值、唤起性内容或心理负荷发生扩张或收缩。但赫斯的研究大多样本量偏小，且未对亮度控制进行规范记录与说明。
本研究通过两项实验（第一项实验<i>N</i> = 182，第二项为预先注册实验<i>N</i> = 147），采用现代实验设备重复了赫斯的五项经典研究。
本研究结果如下：(1) 未支持「观看不同兴趣价值的视觉刺激时，相对于基线的瞳孔直径变化（pupil diameter change with respect to baseline，简称PC）存在性别差异」这一假设；(2) 发现解答难度更高的乘法运算题时，在提交答案前的数秒内PC值更大，最大PC值也更高，但在乘法运算题开始后的固定时间点PC值更小；(3) 未支持「参与者的PC会模仿一对示意图眼睛的瞳孔直径变化，但不会模仿单眼或三眼刺激的瞳孔直径变化」这一假设；(4) 未支持「观看男性试图逃离暴徒的视频时，PC存在性别差异」这一假设；(5) 支持「唤起性词汇相比非唤起性词汇会带来更高PC值」这一假设。
尽管本研究未观察到PC存在一致的性别差异，但补充分析显示，参与者在注视动情区时的眼动存在性别差异。
此外，PC值与参与者注视区域的亮度存在显著相关。
综上，本研究的重复实验验证了赫斯的核心发现：瞳孔会因心理负荷及唤起性刺激发生扩张。而赫斯关于瞳孔模仿以及瞳孔扩张性别差异的假设未得到重复验证。