Not Smart Enough to be Afraid

My dad once teased my sister by telling her that girls are braver than boys. Since she was always interested in any competitive edge she might have over me, her older brother, she perked up with anticipation for the explanation. My dad said, "Yeah ... they aren't smart enough to be afraid".

Now some Japanese researchers have genetically engineered mice that aren’t afraid of cats. Apparently the genetically engineered mice lack certain nasal cells required for them to be instinctively be afraid of cats. Several internet articles are now touting the lack of fear as some kind of enhancement and referring to them as fearless, super and mighty mice. But why?

An interesting side note is that mice infected with protozoan Toxoplasma_gondii also loose their fear of cats. This is favorable to the Toxoplasma because they are only able to reproduce inside a cat host. It's not favorable to the mice (lol).