Reward context determines risky choice in pigeons and humans

Abstract

Whereas humans are risk averse for monetary gains, other animals can be risk seeking for food rewards, especially when faced with variable delays or under significant deprivation. A key difference between these findings is that humans are often explicitly told about the risky options, whereas non-human animals must learn about them from their own experience. We tested pigeons (Columba livia) and humans in formally identical choice tasks where all outcomes were learned from experience. Both species were more risk seeking for larger rewards than for smaller ones. The data suggest that the largest and smallest rewards experienced are overweighted in risky choice. This observed bias towards extreme outcomes represents a key step towards a consilience of these two disparate literatures, identifying common features that drive risky choice across phyla.

Keywords: comparative cognition; decision making; gambling; risk sensitivity.

Figure 1.

Task schematics. (a) Testing arena for pigeons. Pigeons would enter from the start box and choose which half of the arena to enter through the guillotine doors. (b) Stimuli and reward contingencies for pigeons and (c) for humans. For both species, the cues led to either a low–safe reward, low–risky reward, high–safe reward or high–risky reward (from top to bottom). (Online version in colour.)

Figure 2.

Behavioural results. (a) Risk preference (%) for pigeons and (b) for humans and (c) risk sensitivity (%) for pigeons and (d) for humans over blocks of 12 trials. Bar plots (right) show average performance over the final two blocks. (e) Response accuracy (%) on catch trials over blocks of 12 trials for pigeons and (f) for humans. (Online version in colour.)