Do animals have personalities?

Does your cute little pug have a unique personality? See more pictures of dogs.
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­It may seem like a silly question to pet owners. Of course animals have personalities. Just take a trip to your neighborhood dog park, and you'll see those personalities in action: The miniature pinscher marches confidently into the middle of wrestling match among a pack of large dogs, while the mixed breed Labrador tentatively sticks to her owner's pant leg.

Pet owners are quick to attach personalities to their pets. But what do scientists say about this concept? Is it possible for animals to be irritable, adventurous, neurotic or even a mixture of these characteristics?

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To determine whether animals have personalities, we first have to define what a personality is, which is surprisingly difficult. Definitions of personality range from general to precise. For example, personality could merely entail any collection of traits, or might necessitate the traits be "unique," "dynamic" and "enduring" [source: Cottam]. And some psychologists question whether personality is definable at all, judging from the inconsistency of traits in people [source: OUP]. Nevertheless, scientists must know what to look for when they try to decide if an animal has one or not.

Read on to learn how scientists empirically study this concept and what research shows about the extent to which the depth and consistency of an animal's personality can rival a human's.