Despite the experimental support for this hypothesis, it remains controversial. A common critique is that devoutness is easy to fake, such as simply by attending a religious service. However, the hypothesis predicts that people are more likely to join and contribute to a religious group when its rituals are costly. Another critique specifically asks: why religion? There is no evolutionary advantage to evolving religion over other signals of commitment such as nationality, as Irons admits. However, the reinforcement of religious rites as well as the intrinsic reward and punishment system found in religion makes it an ideal candidate for increasing intragroup cooperation. Finally, there is insufficient evidence for increase in fitness as a result of religious cooperation. However, Sosis argues for benefits from religion itself, such as increased longevity, improved health, assistance during crises, and greater psychological well-being, although both the supposed benefits from religion and the costly-signaling mechanism have been contested.