We run an experiment where subjects can physically destroy money-equivalent coupons awarded to them as well as, in a different task, explicitly return money to the experimenter. Subjects affected by experimenter demand effects will con sider both tasks to be identical where, given their stylized nature and the absence of any simple alternative schema to make sense of them, there is an expectation that they should physically destroy or return some of the ssets given to them. The distinctive feature of the destruction task is that the coupons" destruction could not directly benefit the experimenter. This is in contrast to the cash return task or, indeed, any experiment where a money transfer to the budget of the experimenter implic- itly takes place if experimental surplus is destroyed or not obtained. In the cash return task, unlike the destruction task, there can be a money transfer towards the experimenter, so altruism towards the experimenter may potentially affect behaviour and provide an alternative explanation of behaviour relative to experimenter demand effects