As a means of obtaining insights in human psychology, animals are subjected to prolonged isolation as well as being exposed to pain and stress. Such experiments may include withholding postoperative pain-killers. Electric shocks may be administered, whether to observe psychological reactions or to condition the animals to respond to various stimuli.
In the UK in 1986, 25,650 experiments were conducted involving the deliberate induction of psychological stress in animals. Restraining chairs and racks are used for monkeys, cats and dogs to clamp them into a fixed position for periods extending up to months. A wide range of mechanical devices are used to batter animals with hammers or crush them with clamps. Other devices in standard experiments are used to inflict electric shock, extreme heat and extreme cold.