<P> In the mid-20th century, social scientists began to study how and why people imitate ideas . Everett Rogers pioneered innovation diffusion studies, identifying factors in adoption and profiles of adopters of ideas . Imitation mechanisms play a central role in both analytical and empirical models of collective human behavior </P> <P> We are capable of imitating movements, actions, skills, behaviors, gestures, pantomimes, mimics, vocalizations, sounds, speech, etc. and that we have particular "imitation systems" in the brain is old neurological knowledge dating back to Hugo Karl Liepmann . Liepmann's model 1908 "Das hierarchische Modell der Handlungsplanung" (the hierarchical model of action planning) is still valid . On studying the cerebral localization of function, Liepmann postulated that planned or commanded actions were prepared in the parietal lobe of the brain's dominant hemisphere, and also frontally . His most important pioneering work is when extensively studying patients with lesions in these brain areas, he discovered that the patients lost (among other things) the ability to imitate . He was the one who coined the term "apraxia" and differentiated between ideational and ideomotor apraxia . In this basic and wider frame of classical neurological knowledge the discovery of the mirror neuron has to be seen . Though mirror neurons were first discovered in macaques, their discovery also relates to humans . </P> <P> Human brain studies using FMRI (Functional magnetic resonance imaging) revealed a network of regions in the inferior frontal cortex and inferior parietal cortex which are typically activated during imitation tasks . It has been suggested that these regions contain mirror neurons similar to the mirror neurons recorded in the macaque monkey . However, it is not clear if macaques spontaneously imitate each other in the wild . </P> <P> Neurologist V.S. Ramachandran argues that the evolution of mirror neurons were important in the human acquisition of complex skills such as language and believes the discovery of mirror neurons to be a most important advance in neuroscience . However, little evidence directly supports the theory that mirror neuron activity is involved in cognitive functions such as empathy or learning by imitation . </P>

Which of the following is not a source of reinforcement in imitation