This chapter discusses research findings that demonstrate how the environment constrains the processes within the individual. It examines the intriguing interplay of environmental and cognitive factors that characterizes human interaction in distinct situations and institutions. Environmental information provides the input for social-cognitive processes. The chapter uses social hypothesis testing as a unifying paradigm to illuminate the impact of environmental constraints on social cognition. A substantial part of social interaction is driven by two prominent classes of hypotheses that have intrigued philosophers and psychologists alike: beliefs and desires. Social hypothesis testing is constrained by the distribution of stimulus data in the environment, independently of motives and stereotypical beliefs. The outcomes of social hypothesis testing may be subject to systematic biases, even when all cognitive processes within the individual are unbiased, simply because the social and physical environment does not make all information equally accessible.