The Planning, Attention-Arousal, Simultaneous and Successive (P.A.S.S.) theory of intelligence, first proposed in 1975 by Das, Kirby and Jarman (1975), and later elaborated by Das, Naglieri & Kirby (1994) and Das, Kar & Parrilla (1996), challenges g-theory, on the grounds that the brain is made up of interdependent but separate functional systems. Neuroimaging studies and clinical studies of individuals with brain lesions make it clear that the brain is modularized; for example, damage to a particular area of the left temporal lobe will impair spoken and written language's production. Damage to an adjacent area will have the opposite impact, preserving the individual's ability to produce but not understand speech and text.