Tuesday, April 30, 2013

Geek attack: When science, pet ownership and mortality collide

The 9 lives of cats: A brief report on a (pseudo) scientific theory
There is a belief that the common house cat has 9 lives. While this may, on average, be true, I submit that in reality not all cats have 9 lives. I posit that nine is actually the average number of lives that cats, as a population, have. The number of lives each individual cat has, is, in fact on a bell-curve like continuum from 1 to n+1.

Number of lives

In order to arrive at the average of 9 lives, analyses must be done. Taking a statistical mean is the most basic approach: When outliers are dropped from analyses and the number of lives for each cat is summed and divided by the annual incidence of house cat mortality the mean number of lives is approximately 9 (+ 5%). 

However, more sophisticated analyses are required  in order to arrive at the statistical mean of 9.0 and other factors, that have either direct or indirect impact on the odds that a cat will have multiple lives, must be included in the equation. For example, there is anecdotal evidence that the number of lives a cat has may be indirectly proportional to the positive qualities of the cat. Therefore, positive qualities of the cat must be quantified and included as potential modifiers in the analyses. Thus, a cat that is friendly, has wonderful soft fur, does not completely destroy the furniture in the first 6 months in the house, and doesn't try to scratch your eyes out in the middle of the night while you are sleeping is likely to have substantially* fewer lives, perhaps only 1, than a cat that is mean, stinky, and hisses at your significant other every time he/she enters airspace within 75 feet of the cat. The latter cat is likely to have substantially* more lives than the average, say 12. These positive and negative qualities must be statistically counterbalanced by the number of opposing qualities. For example, the first cat described above may also have flea treatment resistant fleas (a negative quality) and the second cat described may submit docilely to handling by young children (a positive quality). These factors, too, must be accounted for in analyses. Hence, when all positive and negative qualities are included and analysed at the population-level, the statistical mean number of lives per cat works out to be 9.0 lives.

Two case studies:
Luna: Awesome cat. Put up with a toddler poking him, a 7 yr old trapping him under the laundry basket, and a 9 yr old carrying him like his legs were broken. Softest fur ever. Like kitten fur but long beyond kittenhood. Willing to let you rub his belly and so friendly that the neighbors referred to him as Mr. Friendly. 
Lived: 15 months


AN: Loved, ok, tolerated only one person (me) and probably only because I fed her. Hated everyone else - passionately. Made "Grumpy Cat" look gregarious. Hissed, spit and pooped every time Michael (husband) came within 20 feet. Ran and hid anytime anyone else came within 50 feet. Managed to live through 2 falls off a 2 storey balcony, getting lost in Vancouver, British Columbia while on a cross-Canada road trip, 4 house moves and one major house renovation, disappearing for 6 months and reappearing literally a step away from death, and 2 dog attacks. 
Lived: 12 years

Not surprisingly there is interest in early prediction of lives in order to reduce the trauma of selecting a cat that, ultimately, may have only a single life. Unfortunately, there is little empirical data in this area and it appears that the early predictive value positive of personality traits is limited. Kittens are endowed with deceptive qualities (e.g., adorable-ness, extreme cuteness) and all appear, on the surface, to have the capacity for attaining, at a minimum, the mean number of lives. More research is needed in this area.

* Note: I use the term "substantially" rather than "significantly" because we lack empirical data of sufficient quality to substantiate statistical significance.

Reported by F. E. Line, PhD, Institute for the BS Scientific Study of Pets, Wild Cat, KY, USA

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