Pupil Diameter Variation in Positive and Negative Emotions with Visual Stimulus

The severely disabled people, e.g. ALS (Amyotrophic Lateral Sclerosis), cannot move their head and hands and desire to communicate with other people. They often feel discomfort because they cannot indicate their intention. To respond their request, the communication devices for disabled people have been developed. However, a contact-type of the communication device using EEG or EMG is burdensome for disabled people because these devices require to put electrodes on their body. Thus, the simplified non-contact type of the communication device is needed. To develop the communication system for severely disabled people, we focused on the characteristics of the pupil diameter variation due to the emotional change and the degree of attention and interest. In this paper, we investigate the pupil diameter variation by using the visual stimuli with positive or negative affective images. From experimental results, the pupil diameter in the positive affective stimulus is significantly smaller than that in the negative one during 2 to 3 second after the visual stimulus. This experimental result indicates that the time variation of the pupil diameter can estimate the emotional states in the positive and negative affections.