Cats are very smart and have about 10 minutes of short-term memory
Purring can improve bone density and promote healing...Because cats have adapted to conserve energy via long periods of rest and sleep, it is possible that purring is a low energy mechanism that stimulates muscles and bones without a lot of energy.
"We found that the crucial factor determining the urgency and pleasantness ratings that purrs received was an unusual high-frequency element--reminiscent of a cry or meow--embedded within the naturally low-pitched purr," McComb said. "Human participants in our experiments judged purrs with high levels of this element to be particularly urgent and unpleasant." When the team re-synthesised the recorded purrs to remove the embedded cry, leaving all else unchanged, the urgency ratings for those calls decreased significantly.
