Preference patterns for skewed gambles in rhesus monkeys

Area of Science:

• Decision neuroscience
• Behavioral economics
• Comparative psychology

Background:

• Standard models of risky choice often overlook the third statistical moment (skewness) of reward distributions.
• Understanding attitudes toward skewness is crucial for refining models of decision-making processes.

Purpose of the Study:

• To investigate rhesus monkeys' preferences for gambles with varying degrees of skewness.
• To determine if skewness influences risky choice independently of mean and variance.

Main Methods:

• Three rhesus monkeys were presented with gambles featuring identical means and variances but differing skewness levels.
• Five skewness distributions were tested: strong negative, weak negative, normal, weak positive, and strong positive.

Main Results:

• Monkeys demonstrated a preference for positively skewed gambles over negatively skewed ones.
• Strongly skewed and normal (unskewed) gambles were preferred over weakly skewed gambles.
• Observed preferences were not explained by single factors like utility curves alone.

Conclusions:

• Rhesus monkeys' risky choices are influenced by the skewness of outcome distributions.
• Decision-making under risk involves multiple interacting factors beyond mean and variance, including skewness.
• These findings necessitate more complex models to capture the nuances of choice behavior.