Via Brad DeLong you won’t want to miss Keith Chen, Laurie Santos, and Venkat Lakshminarayanan, “How Basic Are Behavioral Biases?: Evidence from Capuchin Monkey Trading Behavior.”
Basically they cooked up an ingenuous experiment to see if capuchin monkeys exhibited the same kind of irrational reference effects and loss aversion that Kahneman & Tversky have demonstrated in humans. The answer is, in short, yes. This suggests that these kind of behavioral biases are very deeply rooted since the last common ancestor between humans and monkeys was many millions of years ago. It’s not really a terribly surprising result once you think about it, but definitely a clever line of inquiry.