Complexity, Mental Frames, and Neglect

Many decision contexts require economic actors to learn from something they do not see, yet corresponding evidence on people's cognition is scarce. In a tightly structured and transparent laboratory experiment, many subjects fully neglect what they do not see. A series of treatment variations uncovers that such neglect arises because a particular aspect of complexity induces an excessively narrow mental frame, so that people do not even notice or think about what they do not see. Thus, complexity generates errors in deliberate – and highly confident – statistical reasoning through its effect on how people mentally frame updating problems