In the early 90s Tversky & Shafir observed several violations of rationality in human participants, in particular violation of the disjunction effect and sure-thing principle. This has lead to much work on questioning the rationalist assumptions of Homo economicus.
An example of the violation they saw was in the Prisoners' dilemma: if a person knew their partner defected then also defected (only a 3% cooperation rate), if a person knew their partner cooperated then they usually still defected (only a 16% cooperation rate). However, if they were not sure if their partner defected or cooperated, then they cooperated at much higher rates (a 37% cooperation rate). This violates the naive rationalist expectation of some % between 3 and 16 in the unknown-condition case.
Shafir & Tversky explained this effect through quasi-magical thinking. Even though the participants knew they had no causal effect on their partner's choice, when the choice was unknown they still "did their part" to cause a favorable outcome.
Note that given the false-belief that your actions magically effect the outcome of the other participant's decision, it is no longer irrational to cooperate at a higher rate when you don't know the partner's decision.
However, H.econ is still a popular model in economics. For some, this is a pragmatic choice ("the assumption holds in most situation and allows us to build nice models, so we are okay with it being broken sometimes"), but others have strong justifications for why rationality is still a good principle. What is a popular way for rationalists to defend against the apparent violations of rationality brought up by Tversky and Shafir that go beyond false-beliefs or quasi-magical thinking?
Shafir, E., & Tversky, A. (1992). Thinking through uncertainty: Nonconsequential reasoning and choice. Cognitive Psychology, 24, 449-474. PDF
Tversky, A., & Shafir, E. (1992). The disjunction effect in choice under uncertainty. Psychological Science, 3, 305-309.