Figure 1. Photograph of apparatus used in these studies.

Deciders sat on the left side of the apparatus and could operate the handles while the partner (if present) sat on the right side of the apparatus. Pulling the green handle caused the trays to tip outwards, delivering candies to the two outside bowls (“accepting an offer”). Pulling the red handle caused the trays to tip inwards, delivering candy to the inside bowl (“rejecting an offer”).