Why dogs beg for food?

Who hasn't given -at least once- its dog some food while dining at home? I bet everyone has. Dogs should get an Oscar ward for their great performance at begging for food. The strategies they use are countless. They either sit up

and beg, poke-and-whine, put their face on your thigh with a look that says "Don´t you feel bad about me for letting me starve to death. Look again!" And other well-practiced strategies that have been perfected in time. Some dogs have mastered so well their techniques that they can even look naturally uninterested in receiving food from their target.

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