Sato (1987) gave Japanese students opportunities to harvest trees in a simulated forest for money. When the students equally shared the costs of planting the forest, the result was that

Joe pays ann to mow his lawn and ann mows vanna's lawn by mistake. vanna peers out her window and sees ann mowing, yet says nothing to ann about her mistake since vanna needs to have her lawn mowed. when ann approaches vanna for payment, vanna refuses, arguing that she never asked ann to mow her lawn. under these circumstances, ann can recover payment from vanna under: