Whether we're right-handed or left-handed can have a huge impact on what we subconsciously associate with good and bad. Right-handers, according to psychologists, see things to the right them as being better than things on their left.
Almost everybody has a dominant hand that they use, but it's actually a mystery why that is. After all, we can see both of our hands just as well, and there's no built-in reason why one should work better than the other. But some grabby parrots might hold the deep evolutionary reason behind handedness.