Development of scientific reasoning biases: cognitive versus ego-protective explanations.

Two conflicting perspectives have dominated the literature on self-serving reasoning biases. One maintains that individuals have difficulty objectively processing information relevant to their personal theories because they are reluctant to relinquish their cause-effect beliefs relevant to that domain. The ego-protective view claims that such biases arise because they enhance or protect individuals' self-views. These opposing positions were studied with 5th, 8th, and 11th graders. Scientific reasoning improved with age. Analyses of biases, indicated by ratings of evidence quality and written justifications, yielded mixed results regarding developmental trends in reasoning biases. Both theoretical beliefs and ego-protective motivations predicted reasoning biases. An accuracy motivation led to more complex justifications but failed to reduce reasoning biases. Adolescents appear to selectively apply their scientific reasoning skills.