The question of when to use non-human animal studies as evidence for human behaviour is a tricky one. Because it remains unethical to lesion the brain of a live human to look for a correlation between brain damage and behaviour (at the moment!), animal studies are used in large numbers at the biological approach. However, many people are becoming more disturbed by this than previously as over the years we have come to realise that animals also suffer pain, fear and anxiety as we do, and maybe other ways should be sought to conduct animal studies.
In Psychology Sorted, this is part of the Biological extension: the British Psychological guidelines for working with animals (2012) state that researchers should: Replace animals with other alternatives. Reduce the number of animals used. Refine procedures to minimise suffering. But isn’t how they are used a large part of the problem? After all, observation under natural conditions should be no problem. Xu et al. (2015) researched naturally-occurring depression in macaque monkeys by observing monkeys living at a research base in China in environmental conditions that closely resembled what they would experience in the wild, for nearly 3 years. The monkeys were housed in colonies, usually of two males and 16-22 females, with offspring of under six months.
Instead of unnaturally separating baby chimpanzees from their mothers, as Bowlby and others have done, causing distress, Stanton et al. (2015) ‘picked up poo’: they investigated the effect of maternal stress on the glucocorticoid levels of infant chimpanzees by examining and measuring faecal glucocorticoid metabolite (FGM) concentrations of mothers and babies in the wild. Much less stress for the monkeys, though maybe not for the researchers!
Bearing in mind that we are animals too, it is time empathy stretched to our non-human cousins, and these methods seem to be a first step on the way. See Psychology Sorted for more examples of ethical animal research.