By the late 1980s, neuroscientists had conducted literally hundreds of disconcerting addiction experiments on monkeys and rats. Common practice involved teaching the animals to self-administer drugs (typically cocaine) using a lever, resulting in disturbing addiction-like behaviours. In some studies, the drug lever eventually offered access to alternatives such as food, water or mates. However, drug-addled Rhesus monkeys opted for a fix of coke every single time until they starved themselves to a presumably euphoric death. Addicted lab rats would even walk across electrified grids in order to get a dose of Charlie, and were willing to withstand a much higher voltage to access the drug than to reach their food. Worst of all is that the findings of these rather cruel studies are probably completely invalid. A 1980 paper shows that these behaviours only occur in rats that are kept tethered in small laboratory cages. Rats that were raised in a special enclosure dubbed Rat Park (chockfull of food, hamster wheels, mates and probably a couple of PS4s by the sounds of it) were force-fed water laced with opiates for two months but had a preference for plain water as soon as it was made available to them. In contrast, rats who had lived in jail-like cages their whole lives became heroin addicts at the drop of a hat. Todays life lesson: prevent your kids from doing drugs by installing a hamster wheel in the garden.