• American psychologist John Watson, best known for his controversial experiments with a young orphan named Albert, demonstrated that the acquisition of a phobia could be explained by classical conditioning. A strong proponent of environmental learning, he said: Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I'll guarantee to take any one at random and train him to become any type of specialist I might select...regardless of his talents, penchants, tendencies, abilities, vocations and race of his ancestors.

• Harvard psychologist B. F. Skinner's early experiments produced pigeons that could dance, do figure eights, and play tennis. Today known as the father of behavioral science, he eventually went on to prove that human behavior could be conditioned in much the same way as animals.

• A study in New Scientist suggests that sense of humor is a learned trait, influenced by family and cultural environment, and not genetically determined.

• If environment didn't play a part in determining an individual's traits and behaviors, then identical twins should, theoretically, be exactly the same in all respects, even if reared apart. But a number of studies show that they are never exactly alike, even though they are remarkably similar in most respects.

So, was the way we behave engrained in us before we were born? Or has it developed over time in response to our experiences? Researchers on all sides of the nature vs nurture debate agree that the link between a gene and a behavior is not the same as cause and effect. While a gene may increase the likelihood that you'll behave in a particular way, it does not make people do things. Which means that we still get to choose who we'll be when we grow up.

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