There is a broad contemporary consensus that cognitive variance between people can be conceptualized at three hierarchical levels, distinguished by their degree of generality. At the lowest, least general level there are many narrow first-order factors; at a higher level, there are a relatively small number – somewhere between five and ten – of broad (i.e., more general) second-order factors (or group factors); and at the apex, there is a single third-order factor, "g", the general factor common to all tests. The "g" factor usually accounts for the majority of the total common factor variance of IQ test batteries. Contemporary hierarchical models of intelligence include the three stratum theory and the Cattell–Horn–Carroll theory.