Cats purrs exploit our nurturing instinct by incorporating the same frequency as a baby’s cry.

As of now, communication cross species is something that’s only been dabbled in, comparatively. There are only a few studies that highlight the way animals communicate with their human companions in their “natural” domestic environment. One of the few things that’s been discovered as fact is the way cats manipulate their humans by purring.

Essentially, cats purr to get what they want from human hosts (normally food). Their purr hits the same sensory frequency as an infant’s cry, exploiting the nurturing instinct of humans. A test was conducted that played purrs while cats were seeking food to one group, and played no purrs while cats looked for food to another group.

The group listening to the purrs felt much more discomfort. Embedded within the purr is a higher frequency sound more like a meow. That sound is the actual influential factor in manipulating humans.

(Source)