open mouth staring

I like to consider myself a kind person. However, when faced with an overly chatty person at the checkout counter I become cold, callous, and unresponsive. Unsuspecting cashiers release the Kraken of fury inside me with their relentless attempts to make small talk. No, I do not want to talk to you about my Thanksgiving travels. What I do with my brownie mix is none of your business. Why are you asking about my day? WE DON'T KNOW EACH OTHER! I will politely answer at least one question with a 'fine' or a 'sure', but anything beyond that makes me uncharacteristically and irrationally homicidal. I have tied to figure out why I have such a huge problem with small talk over the exchange of money for goods. So far no acceptable reasons have surfaced.