Abstract
If we want to take sentient non-human animals and their interests seriously, we can try to ask for their consent before using them for human purposes. With mentally competent humans, we speak of informed consent: for them to participate in scientific studies, for example, it is required that they consent explicitly, in full understanding of the risks and benefits. This full understanding cannot be expected from non-human animals. We must therefore look for ways to know what they want and to estimate what they would do if they had a deep understanding of their options and the consequences of these options for themselves and others. This concept is explored by applying it to animal experiments. The most promising method is to gain informed consent by proxy from thoroughly informed competent humans, in combination with seeking assent where possible and being alert to dissent.