A team of psychologists from the University of Sussex in England found that humans were unable to resists a certain kind of purr that they have now called the "solicitation purr". The purr’s sound was analyzed and found to include a high-frequency crying-like element that is thought to trigger a sense of urgency in cat owners, possibly exploiting our innate tendency to nurture offspring.
"I wondered why this purring sounded so annoying and was so difficult to ignore. Talking with other cat owners, I found that some of them also had cats who showed similar behavior," said lead author of the research, Dr Karen McComb was inspired by her own cat’s insistent early-morning purring.
"When humans were played purrs recorded while cats were actively seeking food at equal volume to purrs recorded in non-solicitation contexts, even those with no experience of cats judged the ‘solicitation’ purrs to be more urgent and less pleasant," continued McComb.
When the team re-synthesized purrs to remove the high frequency element, observers scored the purrs as significantly less urgent. However, the team also discovered that in large households where many cats were fighting for attention, individual cats were less likely to use the so-called "solicitation purr".