According to two neurological systems—the behavioral activation system (bas) and the behavioral inhibition system (bis)—explain the differences in an organism's attention to environmental rewards and punishments and in this way shape personality.

The answer is "Reinforcement sensitivity theory".

Reinforcement sensitivity theory or as known Gray's Reinforcement sensitivity theory (RST), explains person’s sensitivity to reward in light of three brain-behavioral systems which motivate the difference. The theory in itself was not presented as a theory of personality but is utilized to investigate and asses various emotions.

Who it was like back then

Americans often speak of their country as one of several large regions.  these regions are cultural units rather than governmental units --  formed by history and geography and shaped by the economics, literature and folkways that all the parts of a region share. what makes one region different from another? a region's multicultural heritage as well as distinct demographic characteristics like age and occupation make regions different and special. within several regions, language is used differently and there are strong dialects. there are also differences in outlook and attitude based on geography.