Affiliations: [a] School of Control Science and Engineering, Shandong University, Jinan 250061, Shandong, China | [b] Department of Psychology, Qilu Hospital of Shandong University, Jinan 250012, Shandong, China | [c] Health & Well Being Academy, Faculty of Medical Science, Anglia Ruskin University, Chelmsford CM1 1SQ, UK
Correspondence:
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Corresponding authors: Licai Yang and Chengyu Liu, both in School of Control Science and Engineering, Shandong University, Jinan 250061, Shandong, China. E-mail:yanglc@sdu.edu.cnandbestlcy@sdu.edu.cn
Abstract: Recent studies have indicated that physiological
parameters change with different emotion states. This study aimed to
quantify the changes of vascular function at different emotion and
sub-emotion states. Twenty young subjects were studied with their finger
photoplethysmographic (PPG) pulses recorded at three distinct emotion
states: natural (1 minute), happiness and sadness (10 minutes for each).
Within the period of happiness and sadness emotion states, two sub-emotion
states (calmness and outburst) were identified with the synchronously
recorded videos. Reflection index (RI) and stiffness index (SI), two widely
used indices of vascular function, were derived from the PPG pulses to
quantify their differences between three emotion states, as well as between
two sub-emotion states. The results showed that, when compared with the
natural emotion, RI and SI decreased in both happiness and sadness emotions.
The decreases in RI were significant for both happiness and sadness emotions
(both P< 0.01), but the decreases in SI was only significant for sadness
emotion (P< 0.01). Moreover, for comparing happiness and sadness emotions,
there was significant difference in RI (P< 0.01), but not in SI (P= 0.9). In
addition, significant larger RI values were observed with the outburst
sub-emotion in comparison with the calmness one for both happiness and
sadness emotions (both P< 0.01) whereas significant larger SI values were
observed with the outburst sub-emotion only in sadness emotion (P< 0.05).
Moreover, gender factor hardly influence the RI and SI results for all three
emotion measurements. This pilot study confirmed that vascular function
changes with diffenrt emotion states could be quantified by the simple PPG
measurement.
Keywords: Emotion recognition, PPG, vascular function, reflection index, stiffness index
