Speaking of cats, when Misty first came to live with us, she once clambered onto my bed and I started rubbing her behind her ear. In response, she rolled the tip of her tongue out and started emitting a low guttural noise. I honestly thought I had damaged the poor animal, and she was in distress. It was explained to me that she was engaging in an activity known as purring that actually meant she was enjoying herself.
How was a person supposed to know that, though? How is one supposed not to become a total neurotic when creatures in her vicinity begin to engage in unexpected behaviors?