A selectionist approach to human ontogenetic development relies on three basic processes: variation, selection, and retention. The approach further implies chat for adaptive behavior to emerge during development, each of these processes is required. Nevertheless, to date variation has been relatively neglected. Some studies show that behavioral variability is enhanced when the appropriate contingencies are present. Moreover, behavioral variability has been shown to facilitate the acquisition of difficult behaviors in animals (e.g., Neuringer, 1993). In the first part of the present paper, we briefly recapitulate the basic tenets of selectionist psychology and attempt to explore the role of behavioral variability in human behavior. In the second pare, its importance in the emergence of intelligence, humor production, and self-regulation is discussed. We present data suggesting that variability enhances intelligent behavior, qualitative humor production and effective self-regulation.