In his paper Emotion and reasoning in human decision-making Edmund Rolls points out that multiple and independent types of reinforcement exist in the human brain, and that they cannot be reduced to a common currency. The present commentary introduces non-specialist readers to this wide variety of reinforcers, each of which carries equal biological value. The evolutionary forces underwriting them reveal much about the causes of our apparently irrational choices – which is why it is important for economists to acquaint themselves with such things.