Monkeys change their preference for the same reward depending on the available altervative, and neurons in the orbitofrotal do the same: when a morsel of apple is preferred to a piece of cereal, the neuron responds more to the apple than to the cereal (Block 1). When a raisin is preferred to a morsel of apple, the neuron responds more to rthe aisin and no longer to the apple (Block 2). View the report here (Tremblay & Schultz 1999).