A detailed comparison of pupil dilation, depending on the sign and the "force" of emotions in presented images and investigation of the role of emotional arousal on pupil dilation were made in the M. Bradley and others experiment (M. Bradley, L. Miccoli, M. Escrig & P. Lang, 2008). The achievement of same results on the Russian sample is difficult, because adaptation of the stimulus material used by database authors showed the presence of cultural specificity in the estimates of the "force", "valence" and "dominance" of images (Vasanov et al., 2011; Vasanov, 2012).
The purpose of this study was to assess the impact of hedonic valence and arousal on the pupil dilation during playback IAPS images.
As an incentive, 60 images were selected from the International System of affective-colored images (IAPS) (Lang et al, 2005). The set included 24 neutral (mean = 5.37 fun, excitement, = 3.56), 18 unpleasant (mean = 2.99 fun, excitement, = 5.29) and 18 pleasant images (mean = 6.97 pleasure, arousal = 4.90). The mean values were obtained from the results of the adaptation of IAPS on the Russian-language sample.
The total sample consisted of 25 people (16 women) aged 18-24. Presentation of images was made using stationary precision recording eye movements system SMI HiSpeed (Germany). Images were displayed on the 19-inch monitor ViewSonic VG 930m in a distance 61 cm from the front of subjects with resolution 1280x1024 pixels. Pupil diameter was measured with a frequency of 500 Hz. Pupil dilation to presented image was calculated as a mean change (from baseline) in the range of 1.5 to 6 seconds after the start of presentation.
The ANOVA results showed a significant difference between the value of pupil dilation during viewing emotionally-colored images compared to neutral (F (2,48) = 7.4937, p = 0.001471). It was found a relatively large increase in pupil diameter while viewing emotionally-colored images, then while viewing neutral pictures (F (1,24) = 15.926 and 7,652, p = 0.000539 and 0.09736). Difference in pupil size while viewing pleasant and unpleasant pictures was not significant (F (1,24) = 0.642, p = 0.4308).
The results show that after the initial light reflex pupil expands to a greater extent in case when subjects view pleasant or unpleasant images compared to neutral images. This confirms the hypothesis that pupil diameter increases while perception stimulus’s with higher ratings of arousal, regardless of their hedonic valence.
Bradley, M. M., Miccoli, L., Escrig, M. A. & Lang, P. The pupil as a measure of emotional arousal and autonomic activation // Psychophysiology J. – 2008. – № 45. – pp. 602-607.
Васанов А.Ю. Оценка эмоционально-окрашенных фотоизображений IAPS. Сравнение одно- и двумерной модели валентности: Тез. к восьмому международному междисциплинарному конгрессу «Нейронаука для медицины и психологии». Судак, 2-12 июня 2012 г.
Васанов А. Ю., Марченко О.П., Машанло А.С. Проверка стандартных показателей эмоционально окрашенных фотоизображений IAPS на русской выборке // Экспериментальная психология. - 2011. - №3. – С. 126-132.