A student who strongly believes that genetic influence is the major contributor to human personality is analyzing data gathered about identical twins who had been separated at birth and reunited in adulthood. The student observes many striking similarities in personality and habits within the twin pairs but does not notice differences within the twin pairs that might argue against the student’s belief. This student’s behavior illustrates which of the following?

This student’s behavior illustrates confirmation bias. In research, confirmation bias is an experimental error that is introduced when a researcher tends to tailor or focus his research attention and observations in a way that confirms his preconception of the research topic.

This student already strongly believes that genetic influence is a major contributor to personality and hence focuses on the similarities between the twins while ignoring the dissimilarities between them which could counter his preconception about genetic influences on personality. He is biased in his confirmation.