Pupil Dilation and Heart Rate as Responses to Ad Exposure
Pupil dilation and heart rate can show variations in emotional arousal, mental activity, and cognitive processes [1, 2]. Eyes and heart can show what draws our attention, what excites us, and reveals our desires, fears, and preferences. The main research question of the presented study is whether the effects of advertising exposure can be measured based on physiological responses, such as pupil dilation and heart rate. In contrast to self-reports, physiological responses are less prone to bias.
The experimental study on 33 participants (age M = 21.70, SD = 2.36; female = 68%) was conducted in a laboratory setting to investigate the physiological responses of pupil dilation and heart rate to ads. The materials were four in-video ads with varying levels of engagement (lower/higher) as the main selection criteria. The ads were randomly assigned to the participants.
Statistical analysis was performed in Python using the Scipy and open-cv libraries. A Pearson coefficient showed a slight negative correlation between pupil size and heart rate, r(33) = -.16, p = .08. A Kruskal-Wallis test showed a significant effect of ad exposure on pupil dilation (H = 75.38, p < .001) but not on heart rate (H = 6.60, p = .085).
We tested for the effects of ad brightness on pupil dilation, as the latter can be affected by light. There is a significant difference in pupil dilation for Ad1 and Ad2, but no difference in brightness (Ad1: M = 0.26, SD = 0.37; Ad2: M = 0.26, SD = 0.26), no difference in pupil dilation for Ad2 and Ad3, but a big difference in brightness (Ad2: M = 0.26, SD = 0.26; Ad3: M = 0.48, SD = 1.8), and a difference both in pupil dilation and brightness between Ad4 (M = 0.6, SD = 1.9) and the other ads. The results are inconclusive and further research is needed to evaluate pupil dilation as a reliable measure of ad exposure effects.
Future research will include other physiological responses, such as electrodermal activity, leading to a better evaluation of ad exposure effects. Integrating physiological measurements with traditional methods (e.g. surveys) can help overcome bias and better identify consumer behaviour, needs, motivations, and preferences.
Physiology measurements can be used in future marketing strategies and technologies related to ad exposure effects and consumer behaviour.
 P. van der Wel and H. van Steenbergen, “Pupil dilation as an index of effort in cognitive control tasks: A review,” Psychonomic Bulletin and Review, 25(6), 2018. https://doi.org/10.3758/s13423-018-1432-y
 T. Pham; Lau, Z.J.; Chen, S.H.A.; Makowski, D., “Heart Rate Variability in Psychology: A Review of HRV Indices and an Analysis Tutorial,” Sensors, 21(3998), 2021. https://doi.org/10.3390/s21123998