Meehl theorized that clinicians would make more mistakes than a mechanical prediction tool created to combine clinical data and arrive at predictions. Within his view, mechanical prediction approaches need not exclude any type of data from being combined and could incorporate coded clinical impressions. Once the clinical information is quantified, Meehl proposed mechanical approaches would make 100% reliable predictions for exactly the same data every time. Clinical prediction, on the other hand, would not provide this guarantee. Meta-analyses comparing clinical and mechanical prediction efficiency have supported Meehl's (1954) conclusion that mechanical methods outperform clinical methods. In response to objections, Meehl continued to defend algorithmic prediction throughout his career and proposed that clinicians should rarely deviate from mechanically-derived conclusions. To illustrate this, Meehl described a “broken leg” scenario in which mechanical prediction indicated that an individual has a 90% chance of attending the movies. However, the “clinician” is aware that the individual recently broke his leg, and this was not factored into the mechanical prediction. Therefore, the clinician can confidently conclude the mechanical prediction will be incorrect. The broken leg is objective evidence determined with high accuracy and highly correlated with staying home from the movies. Meehl argued, however, that mental health professionals rarely have access to such clear countervailing information as a broken leg, and therefore rarely if ever can appropriately disregard valid mechanical predictions. Meehl argued that humans introduce biases when making decisions during clinical practice. For example, clinicians may seek out information to support their presuppositions, or miss and ignore information challenging their views. Additionally, Meehl described how clinical judgment could be influenced by overconfidence or anecdotal observations unsupported by empirical research. In contrast, mechanical prediction tools can be configured to use important clinical information and are not influenced by psychological biases. In support of this conclusion, Meehl and his colleagues found that clinicians still make less accurate decisions than mechanical formulas even when given the same mechanical formulas to help with their decision-making. Human biases have become central to research in diverse fields including behavioral economics and decision-making. Meehl was elected president of the American Psychological Association in 1962. In his address to the annual convention, he presented his comprehensive theory about the genetic causes of schizophrenia. This conflicted with the prevailing notion that schizophrenia was primarily the result of a person's childhood rearing environment. Meehl argued schizophrenia should be considered a genetically-based neurological disorder manifesting via complex interactions with personal and environmental factors. His reasoning was shaped by the writings of psychoanalyst Sandor Rado as well as the behavioral genetics findings at the time.