[This is post 6 in the "Structure and Cognition" series; links to all the posts can be found here ] I’ve been arguing that although human cognition seems very complicated, much of it can be better understood as the result of simple processes. This story is not new in psychology, but the standard telling focuses on heuristics and human irrationality. In this standard account, we frequently use simple cognitive mechanisms, but this is a huge problem and leads to predictable irrationality. Our only hope is to effortfully engage deliberative, System 2 thinking to help us. The alternative view is based on two important points. First, real world problems are so complicated that no amount of processing can arrive at optimal solutions. No matter how impressive System 2 might be, the real world is orders of magnitude more complicated. Second, simple processes like heuristics can work well not despite their simplicity, but because they are able to exploit structure in the environmen...