When we take the time to step back and treat rats as individuals – as Fouts did with Booee and Goodall did with David Greybeard – we can come to see rats not as research tools, but as sentient beings who have the capacity to enjoy rich emotional lives. As researchers found out more about primates, they realised that primates required protection, leading to welfare legislation and oversight committees. However, as we find out more about rats, rather than changing the way we treat them, science is repeating the mistakes made in the early days of primate research. Harlow’s ethically questionable logic was that monkeys are similar enough to humans to be used as models for human mental disorders, but not similar enough to warrant the same levels of protection from harm. The justification for the rat research is that rats are similar enough to humans to serve as good models of human health, including mental health, but not similar enough to warrant any legal protection from harm. Some scientists even welcome this lack of care toward rats, who with other rodents are considered to ‘offer a cheap, convenient and ethically less controversial alternative to non-human primates in the study of social cognition’. While the free use of rats in research might be less ethically controversial than the use of primates – given the relative lack of rat ambassadors – it is not more ethically justifiable.
— Read on aeon.co/essays/why-dont-rats-get-the-same-ethical-protections-as-primates