By Robert Ornstein

The Author

Psychologist Robert Ornstein’s work has won awards from more than a dozen organisations, including the American Psychological Association and UNESCO. His research on the specialisation of the brain advanced our understanding of how we think. He has published 26 books on the human mind and brain and their relationship to thought, health and individual and social consciousness, which have sold over six million copies and been translated into a dozen other languages. Dr Ornstein has taught at the University of California Medical Center and Stanford, and lectured at 200 universities. He is the president of the Institute for the Study of Human Knowledge (ISHK), which brings important discoveries on human nature to the public.

This article is an introductory shortened version of the one prepared for free download 2006, based on Dr Ornstein’s 1973 ICR lecture and available from the ICR website:


Few subjects in modern psychology are more fascinating, and more elusive, than hemispheric brain specialisation. Despite being suggested in ancient times and, as Robert Ornstein shows, scientifically proposed in 1836, it was only in the 1950s and 1960s that the model of the brain as having two distinct modes of operation really took hold in the West.

Ornstein is careful to state that the hemispheres are not subject-specific – both can handle any subject – rather, they are method-specific. The right hemisphere operates in a holistic, intuitive way that seems outside time in some senses, whilst the left brain operates in an analytical, deliberate, systematic fashion which more closely resembles the step-by-step functioning of a computer program. The left brain moves towards its final goal very much within the temporal normality of everyday experience, whilst the right brain can make astonishing leaps and is more sensitive to the subjective sensation of time ‘standing still’.

There is a new urgency, though, about Ornstein’s work. The rise of texting, email, and social media has resulted in a significant move towards a more ‘left-brain’ world. We may even discover that mental imbalances follow hemispheric imbalances, that an environment that is modelled too closely on what is ‘obvious’ and ‘convenient’ – an emphasis on ‘left-brain’ usage – can become imbalanced and even toxic in certain ways.

Physiological Studies of Consciousness

For the past several years we and our colleagues at the Langley Porter Neuropsychiatric Institute in San Francisco have been studying the biological mechanisms underlying two modes of consciousness.

We have primarily studied brain electrical activity (EEG) and eye movements. In this paper we will review some of the history of the lateralization of brain function and describe two recent experiments [available on the downloadable version of this article].

Long history

The asymmetrical localisation of cognitive function in the human brain has long been studied. Language was ascribed to the left hemisphere by Dax in 1836 (Brain, 1956).

Since then, clinical work with brain-damaged patients has continued to differentiate the cognitive functions of the hemispheres (Semmes et al., 1955; Milner, 1965a; Luria, 1966; Corkin, 1965). For example, right temporal lobectomy produces a severe impairment on visual and tactile mazes.

In contrast, left temporal lobectomy of equal extent produces little deficit on these tasks, but impairs verbal memory (Milner, 1965a, Corkin, 1965).

In general, clinical work has found verbal and arithmetical functions (analytic, linear) depend on the left hemisphere, while spatial relationships (holistic, gestalt) are the special province of the right hemisphere.

Split brains

Sperry, Gazzaniga, Bogen and their associates (1969, Levy, 1970, Bogen, 1969) have had a unique opportunity to study the specialisation of the two halves of the brain isolated from each other.

They worked with patients who had undergone surgical section of the corpus callosum for the treatment of epilepsy. These ‘split-brain’ patients were tested with special apparatus to insure unilateral presentation of the task.

Sperry, Gazzaniga and Bogen have been able to establish that each hemisphere can function independently and is independently conscious.

Learning and memory are found to continue separately in each hemisphere. The right hand literally does not know what the left hand is doing.

The one from the other

Both halves independently sense, perceive and conceptualise. Unilateral associations between tactual, visual and auditory sensations remain. In these patients, the left hemisphere is capable of speech, writing and mathematical calculation, and is severely limited in problems involving spatial relations.

The right hemisphere has use of only a few words and can perform simple addition only up to ten, but can perform tasks involving spatial relationships and music patterns.

It is important to emphasise that what most characterises the hemispheres is not that they are specialised to work with different types of material, (the left with words and the right with spatial forms); rather each hemisphere is specialised for a different cognitive style; the left for an analytic, logical mode for which words are an excellent tool, and the right for a holistic, gestalt mode, which is particularly suitable for spatial relations as well as music.


The difference in cognitive style is described in a recent paper by Levy, Trevarthen, and Sperry, 1972: ‘Recent commissurotomy studies have shown that the two disconnected hemispheres, working on the same task, may process the same sensory information in distinctly different ways, and that the two modes of mental operation involving spatial synthesis for the right and temporal analysis for the left, show indications of mutual antagonism (Levy, 1970).

The propensity of the language hemisphere to note analytical details in a way that facilitates their description in language seems to interfere with the perception of an over-all Gestalt, leaving the left hemisphere ‘unable to see the wood for the trees’.

This interference effect suggested a rationale for the evolution of lateral specialisation . . .’ (Levy, et al., 1972) However, great caution should be exercised in making the inference of lateral specialisation of cognitive function in normal people from lesion studies alone.

Lateral specialisation

One might consider whether the ‘split’ functions are due in some part to the radical surgery, or to other disturbances in these patients. The study of neurological disorders or surgical preparations casts light on normal functioning, but the most important and most practical question is whether the normal brain, engaged in everyday activities, is organised around lateralization of cognitive function.

Recent research with normal subjects provides support for the inference that the intact brain does in fact make use of lateral specialisation.

Verbal and non-verbal

With normal subjects, Filbey and Gazzaniga have measured the time required for information presented to one hemisphere to be acted upon by the other. A verbal reaction to information presented to the non-verbal right hemisphere took longer than a non-verbal response. (Filbey and Gazzaniga, 1969).

McKeever found faster tachistoscopic word recognition for words projected to the left hemisphere (McKeever and Huling, 1970). In dichotic listening tasks, normal subjects have better recall for verbal material presented to the right than to the left ear and better recall for melodies presented to the left. (Kimura, 1961).

In the past three years we have applied electrophysiological methods to the study of this lateral specialisation in normal people. By studying EEG asymmetry we were able to distinguish two cognitive modes as they occur in normal subjects using simple scalp recording (Galin and Ornstein, 1972).

Task-dependent asymmetry

In brief, we examined the EEGs of subjects performing verbal and spatial tasks to determine whether there were differences in activity between the appropriate and inappropriate hemispheres. We recorded from the temporal and parietal areas since clinico-anatomical evidence indicates that these areas should be differently engaged in these tasks.

We found that during verbal tasks the integrated whole-band power in the left hemisphere is less than that in the right, and during spatial tasks the integrated power in the right hemisphere is less than in the left. Most of the task-dependent asymmetry appeared to be in the alpha band. Our method of analysing the ratios of right to left EEG power was adopted by McKee, Humphrey and McAdam (1973) in a study contrasting musical and verbal processing.

They confirm our general finding that the ratio is higher in the verbal tasks compared to the non-verbal tasks. Other laboratories have used electrophysiological techniques such as evoked potentials and DC potentials.

Further proof

Buchsbaum recorded averaged visual evoked potentials from the left and right occipital areas in response to words and geometric stimuli (Buchsbaum and Fedio, 1969). The responses to these two classes of stimuli were the same in the right hemisphere, but different in the left hemisphere. Wood et al. (1971) found similar results with auditory stimuli; subjects listened to verbal stimuli under two conditions; to process them for speech cues (stop consonants) and for non-speech cues (pitch).

The evoked responses were the same in the right hemisphere, but different in the left hemisphere.

In summary, studies with brain injured, neurosurgical, ‘split brain’ and normal subjects confirm lateral specialisation for cognitive function.

Language processing and mathematical tasks depend heavily upon the left hemisphere, while problems in spatial relations depend upon the right.

Right-handed, left-handed

The lateralization of cognitive functions described above is characteristic of right handed people.

The cerebral lateralization of left handed people is more complex. Hecaen (1964, 1971) has provided an extensive review of the neurological literature and a summary of his own clinical studies, and concluded that left-handers show a greater cerebral ambilaterality, not only for language, but also for gnosic and praxic functions.

Hecaen distinguishes between left handedness which is familial, and that which follows a perinatal injury to the left hemisphere. The familial type may or may not have reversed language lateralization. To our knowledge there have been no attempts to quantitatively evaluate the interaction between the verbal-analytic and spatial-holistic cognitive systems in normal daily activities.


Our opinion is that in many ordinary activities normal people simply alternate between cognitive modes rather than integrating them. These modes compliment each other but do not readily substitute for each other.

Although it is possible to process complex spatial relationships in words, it would seem much more efficient to use visual-kinaesthetic images. For example, consider what most people do when asked to describe a spiral staircase; they begin using words, but quickly fall back on gesturing with a finger.

The interference hypothesis

Processing in the inappropriate cognitive system may not only be inefficient, it may actually interfere with processing in the appropriate system.

This ‘interference hypothesis’ is supported by a study of left-handed subjects who were presumed to have bilateral language representation (Levy, 1969). Levy compared left-handed and right-handed subjects with equal WAIS verbal scores and found that the left handers had significantly lower performance scores, which she attributed to interference from the presumed ambilaterality of language.

Her observation has been confirmed by Miller (1971). Similarly, in a group of patients in whom right hemisphere language was demonstrated with carotid amytal, Lansdell (1969) found a negative correlation between language ability and spatial performance scores.

Brooks (1970) presents additional support for the hypothesis of ‘inter-hemispheric interference’. Reading a description of spatial relations interferes with the subsequent manipulation of those spatial relations.

Den Hyer and Barrett (1971) demonstrated selective loss of spatial and verbal information in short term memory by means of spatial and verbal interpolated tasks. Levy has in fact suggested that verbal and non-verbal functions evolved in opposite hemispheres to reduce interference of one system with the other (Levy, 1969).


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