This has led to some interesting neurological findings: Neural correlates of interspecies perspective taking in the post-mortem Atlantic Salmon
http://prefrontal.org/files/posters/Bennett-Salmon-2009.jpg via http://www.metafilter.com/85322/The-Wisdom-of-Salmon
An extreme example, illustrating a common mistake in the field. https://xkcd.com/882/ has the gist of it.