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number of mistaken responses (accuracy), (b) mean reaction time (RT), and (c) the standard deviation of RT (RTSD) over n trials (Deary, 2000; Jensen, 1998, 2007). Accuracy is usually very high in these tasks, RT reflects processing speed, and RTSD measures the intraindividual variability in RT. Speed and efficiency of information processing in these elementary cognitive tasks must be distinguished. Speed is measured by RT, whereas RTSD captures processing efficiency. The processing efficiency component of speed tasks has been linked to the periodicity in the excitatory potential of neurons. The speed of transmission from neuron to neuron depends on both the speed of axonal and synaptic conduction and the probability that impulses are delayed by oscillation of the neurons’ excitatory potentials. The phase of excitatory potential –oscillating below and above the threshold of excitation by a given stimulus—is random with respect to the onset of the stimulus, and, therefore, the probability that the stimulus will be propagated varies depending on whether the potential is above or below the excitability threshold. This is the rule: the faster the oscillation, the shorter is the average difference in time between the quickest and slowest reactions to the stimulus (Anderson, 1994; Jensen, 1998; Vernon et al., 2000). Jensen (1998) argues that periodic oscillation of the action potentials of assemblies of neurons could underlie the variability in speed tasks. This neural oscillation model is thought to represent neural noise (Barrrett et al., 1990; Callaway, 1979; Fairbank et al., 1991; Jensen, 1992). By analogy, «the static and cross talk on a bad telephone line, reduces the efficiency of communication and thereby increases the time of the callers’ conversation, because many words and phrases have to be repeated to get the message across» (Jensen, 1998, p. 255).