1. A method of using electrical brain responses to quantitatively evaluate effectiveness and speed of cognitive brain functioning for the purpose of measuring at least one of the following: level of cognitive functioning, cognitive deficits; efficacy of treatments for cognitive deficits; mental deterioration due to disease processes; mental deterioration due to trauma; mental deterioration due to aging; mental deterioration due to Alzheimer's disease; and efficacy of treatments for said mental deterioration; comprising: assigning a cognitive task that has cognitive and non-cognitive aspects, wherein said cognitive task includes recognizing and responding to autobiographically relevant items or events experienced during at least one life experience of a subject as a means at least to invoke the subject's episodic memory; and a difficulty of said cognitive aspect depends on at least one factor affecting memorability of the items; and wherein said cognitive aspect also involves classifying and differentially responding to the items according to a classification rule, and a difficulty of said cognitive task depends on at least one of the classification rule, the items to be classified, a number of the items to be classified, and a type of the items to be classified; measuring behavioral output of said cognitive task and a timing of said output; measuring and analyzing brain responses that provide an index of the effectiveness or speed of specific cognitive processes; and quantitatively evaluating the effectiveness and speed of cognitive brain functioning and deficits based on said brain responses and said analyzing.