Interpersonal Comparison of Utility by Measuring Neural Activity

Aggregating welfare across individuals is a fundamental problem in our society. There is no rational aggregation procedure without interpersonally comparable utility (Arrow’s impossibility theorem). However, scientific methods for interpersonal comparison of utility have thus far not been available. Here, we have developed such a method based on brain signals that correlated with changes in expected utility weighted by subjective probability. The signal was larger for participants with lower household incomes than for those with higher household incomes and their ratio coincided with the estimates by “impartial spectators”. These findings suggest that our interpersonal comparison method enables scientifically reasonable welfare aggregation.