Figure 6. Compound strategies: suicide.

(A) Distance difference between Pac-Man and closest pellet before and after the death is smaller in suicides than in failed evasions. Vertical dashed lines denote means. ***p<0.001, two-sample t-test. (B) Average distance between Pac-Man and the ghosts was greater in suicides than in failed evasions. Vertical dashed lines denote means. ***p<0.001, two-sample t-test. (C) The monkeys fixated more frequently on the ghosts and the pellets in suicides than in failed evasions. Vertical bars denote standard errors. ***p<0.001, two-sample t-test. (D) The monkeys’ pupil size decreased before Pac-Man’s death in suicides. The black bar near the abscissa denotes data points where the two traces are significantly different (p<0.01, two-sample t-test). Shades denote standard errors at every time point. See Figure 6—figure supplement 1 for the analysis for individual monkeys.

Figure 6—figure supplement 1. Suicides in Monkey O (left) and Monkey P (right).

(A, E) The distance difference between Pac-Man and closest pellet before and after the death is smaller in suicides than in failed evasions. Vertical dashed lines denote means. ***p<0.001, two-sample t-test. (B, F) The average distance between Pac-Man and the ghosts was greater in suicides than in failed evasions. Vertical dashed lines denote means. ***p<0.001, two-sample t-test. (C, G) The monkeys fixated more frequently on the ghosts and the pellets in suicides than in failed evasions. Vertical bars denote standard errors. ***p<0.001, two-sample t-test. (D, H) The monkeys’ pupil size decreased before Pac-Man’s death in suicides. The black bars near the abscissa denote data points where the two traces are significantly different (p<0.01, two-sample t-test). Shades denote standard errors at every time point.

Figure 6—video 1. Suicide game segment.

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Monkey’s moving trajectory, actual and predicted actions, and labeled strategies are plotted in this suicide game segment. Monkey’s real-time saccade position is plotted as a moving white dot. In this trial, the monkey moved Pac-Man toward a normal ghost to be eaten on purpose. The local pellets were scarce, and the remaining pellets were far away. Thus, the death of Pac-Man resets the game and returns Pac-Man and the ghosts to their starting positions, making suicide a more advantageous compound strategy.

Figure 6—video 2. Failed evasion game segment.

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Monkey’s moving trajectory, actual and predicted actions, and labeled strategies are plotted in this failed evasion game segment. Monkey’s real-time saccade position is plotted as a moving white dot. In this trial, the monkeys were adopting the evade strategy but failed to escape from the ghosts.