<p>The phenomenon of increased risk-taking in the last round of a set of risky decision-making tasks is called the ending effect. Recent empirical studies proposed an emotional motivation account to explain the ending effect. That is, the pursuit of an emotionally satisfying ending leads to the increase of risk-taking. However, previous studies have mostly examined the ending effect at the behavioral level, there is yet no physiological evidence to examine the emotional motivation account. To fill in this gap of knowledge, the current study examined the emotional motivation account at the physiological level by recording pupil diameters, which reflect the activation of emotional motivation. Participants were randomly assigned to complete eight rounds or ten rounds of risk decision tasks while having their eyes tracked. The results showed a significant interaction between round and group on pupil diameter. Specifically, there was no significant difference between the first six rounds and the 8th round in the experimental group. For the control group, the pupil diameter of the first six rounds was significantly larger than the 8th round. Perceived ending may have sustained emotional arousal. This finding provides qualified physiological support for the emotional motivation account of the ending effect.</p>