Pat Gunning wrote:   
> And is not that distinguishing feature the human ability   
> to choose? More specifically, isn't the distinguishing   
> feature the ability to identify alternatives and choose   
> among them in the way that individuals regard as most   
> suitable?   
  
That's getting a little too metaphysical for me.  
More concretely, people share choice behaviors with animals.    
E.g., http://www.som.yale.edu/Faculty/keith.chen/papers/LossAversionDraft.pdf  
(Some details below.)  
  
Cheers,  
Alan Isaac  
  
    The Evolution of Our Preferences: Evidence from   
    Capuchin-Monkey Trading Behavior  
  
    Keith Chen joint with Venkat Lakshminarayanan & Laurie Santos  
  
    Abstract:  
    Behavioral economics has demonstrated systematic   
    decision-making biases in both lab and field data. But   
    are these biases learned or innate? We investigate this   
    question using experiments on a novel set of subjects --   
    capuchin monkeys. By introducing a fiat currency and   
    trade to a capuchin colony, we are able to recover their   
    preferences over a wide range of goods and risky   
    choices. We show that standard price theory does   
    a remarkably good job of describing capuchin purchasing   
    behavior; capuchin monkeys react rationally to both   
    price and wealth shocks. However, when capuchins are   
    faced with more complex choices including risky gambles,   
    they display many of the hallmark biases of human   
    behavior, including reference-dependent choices and   
    loss-aversion. Given that capuchins demonstrate little   
    to no social learning and lack experience with abstract   
    gambles, these results suggest that certain biases such   
    as loss-aversion are an innate function of how our   
    brains code experiences, rather than learned behavior or   
    the result of misapplied heuristics.