Like the clinical infant, the observed infant is not a real person or even a real set of persons. Instead, the observed infant is a theoretical construct composed from observations of infant psychology made by developmental psychologists through experiments with infant behavior. For a long time, the observed infant was rather crude due to the dominance of psychological theories that saw reasoning about internal mental states as fundamentally unscientific. Since subjective mental states cannot be directly observed, then it was not the proper subject of science.