Despite challenges to Skinner's interpretation of the root of his pigeons' superstitious behaviour, his conception of the reinforcement schedule has been used to explain superstitious behaviour in humans. Originally, in Skinner's animal research, "some pigeons responded up to 10,000 times without reinforcement when they had originally been conditioned on an intermittent reinforcement basis."[25] Compared to the other reinforcement schedules (e.g., fixed ratio, fixed interval), these behaviours were also the most resistant to extinction.[25] This is called the partial reinforcement effect, and this has been used to explain superstitious behaviour in humans.