Experiments in Personality: Volume 1 (Psychology Revivals)

Psychogenetics and psychopharmacology

H. J. Eysenck, H.J. Eysenck

• Publisher: Routledge
• Year: 2013
• Print ISBN: 9780415842433
• eBook ISBN: 9781135017736
• Topic: Psychology
• Subtopic: Experimental Psychology
• Index: Psychology

Originally published in 1960, the two volumes of Experiments in Personality report a number of experiments in psychogenetics, psychopharmacology, psychodiagnostics, psychometrics and psychodynamics, all of which formed part of the programme of research which had been developing from the late 1940s at the Maudsley Hospital. Presenting the studies together in a book, rather than the more usual route of journal articles, was itself felt to be an experiment at the time, especially given the wide area covered. The decision was deliberate because all the studies reported formed part of a larger whole, which would have been lost if published separately.

Volume I looks at psychogenetics and psychopharmacology.

Part One
Experiments in Psychogenetics

Applications of Biometrical Genetics to the Inheritance of Behaviour

P. L. Broadhurst

1
Introduction¹

WHAT follows is an account of a programme of work in the psycho-genetics² of some aspects of emotional behaviour in the rat, begun in 1954 and still in progress. While the intention has been to make it complete in itself, reference to related investigations published elsewhere will be necessary from time to time. However, the main body of the purely psychogenetical work has not been previously discussed, except in preliminary reports (Broadhurst, 1958d, 1959), and the present account covers the work up to December 1958. It is written for psychologists, so that a knowledge of statistical procedures is assumed, but none of genetics beyond simple Mendelian formulations. Accordingly an attempt will be made, as it becomes necessary, to sketch the main principles of the methods of biometrical genetics which are used. This, however, can be no substitute for the detailed consideration by interested readers of the assumptions, methods and controversies of biometrical genetics, some of which may be sampled in the references given.

Survey of Psychogenetics

The pioneer work in this field of behaviour study, as in so many others, is due to the genius of Sir Francis Galton. His studies on the inheritance of mental capacities, begun in 1869 and including the significant contribution of the twin-study method, initiated an interest in this field which has rarely lost momentum since. It is not the present intention to dwell on the efforts to assess the size and nature of the genetical influence on human behaviour, but rather to evaluate the contribution that experimental work using animal subjects has made. But in passing it should be noted that progress in the former, real though it has been, still leaves much to be desired. Thus Cattell, whose recent work using multiple variance analysis (1953, 1959a, 1959b; Cattell, Blewett, and Beloff, 1955) represents a methodological advance in this field on the earlier use of the twin study and familial correlation methods independently of each other, writes as follows: ‘No argument is necessary to convince the scientific psychologist that personality theory, clinical psychology, and learning theory are bereft of knowledge of about half of the influences at work, in the absence of an understanding of heredity. All learning and adjustment is limited by inherent properties of the organism. Only the unintelligent or the uninformed clinician or educator practices individual guidance without estimating what degree of difficulty a given adjustment or performance offers a particular personality. The general laws of psychology, explaining the genesis of abilities, temperament, and dynamic traits, need also to be more concerned with maturational trends, innate dispositional rigidities, and the effects due to hereditary limits’ (Cattell, Stice, and Christy, 1957, p. 143).

But in turning to the animal field, which is an essentially more tract able one for experimental psychogenetics, because of the availability of genetically pure lines, and the control possible over mating, enabling the formation of others, it must be confessed that the situation is only slightly better. Apart from a few significant exceptions in the last decade, it is still possible to agree with Stone when he wrote: ‘To many of us who have worked for a long time in the field of comparative psychology it is a matter of shame and regret that only an amateurish beginning has yet been made by psychologists in the utilization of pure lines of animals in fundamental research in the nature-nurture area’ (1947, p. 344).

Methods of comparative psychogenetics

Psychological authorities are agreed that there are two main approaches to the study of the inherited determinants of behaviour in animal subjects (Stone, 1947; Hall, 1951; Russell, 1953a). The first is by selection and the second by the analysis of the characteristics displayed by different, preferably pure, strains. In a sense these methods are complementary; the object of the first, selective breeding, is to establish lines which differ in the behavioural characteristics for which they have been selected. The fact that such selection is possible is strong presumptive evidence that the characteristic in question has some hereditary determination. The second method employs established strains, ones selected originally for differences other than those in which a psychologist is interested, such as coat-colour, tumour susceptibility, etc. The criterion for purity of strain in mammals is usually taken as twenty consecutive generations of mating brother with sister (though see Carpenter, Griineberg, and Russell, 1957; Biggers, McLaren, and Michie, 1958) and can be checked by tissue transplants (Billingham, and Silvers, 1959). Again, the fact of differences between different genetically pure strains is presumptive evidence of the influence of heredity upon behaviour.

The end point reached by the use of both methods is the same—its purpose is, or should be, to arrive at a position from which a genetical analysis can commence using the standard procedures of, for example, cross-breeding with pure strains and the analysis of heritability from selectively bred ones. Both these methods have been employed in the present work.

Strain differences

The use of different strains, particularly of rats and mice, has long been a favourite method of psychogenetics. Bagg was a pioneer in the application of ‘the methods of genetics to the study of conduct’. He found strain differences between strains of mice in various learning situations (1916, 1920). The Yerkes, (1913, 1916) and Utsurikawa (1917) compared pure and outbred strains of rats, the latter noting that individual differences exceed strain differences. Sadovnikova-Koltzova crossed albino with wild grey rats and studied the first and second generations of offspring of this cross by means of the Hampton Court maze (1926), publishing further papers later (1928, 1929, 1931, 1933).

The studies on mice of Vicari (1929) and Dawson (1932) show more genetical sophistication but are deficient psychologically. The maze performance measures as used by Vicari are unnecessarily complicated characteristics for study, and it is not surprising that her analyses of three crosses from among four inbred strains did little to clarify the genetics of maze learning, especially since one of her strains, ‘waltzer’ mutant, is now known to be complex genetically (Griineberg, 1952). Dawson used as a measure of ‘tameness’ the speed of unrewarded running in a straight alley, a test which bristles with difficulties to administer and interpret, but for which he claims a reliability of 0.92. He used the standard type of Mendelian analysis with mammals by crossing the parental strains, usually designated P₁ and P₂, to produce a first filial or hybrid generation (Fj), a second filial generation bred from the first (F₂), and then making the backcrosses from F₁ to the P₁ and the P₂-B₁ and B₂ respectively. He does not specify the degree of genetical homogeneity (homozygosity) of the four strains—three tame and one wild—which he used, thus rendering only tentative his conclusions that wildness is determined by a few genes which are dominant and which have no linkage for sex, or for any of the five genes which he knew to be carried by his strains. That this absence of linkage is probably true for one of the genes, ‘short ear’, has recently been confirmed (Bundy, 1950).

The tendency of young rats to climb up an inclined plane (negative geotropism) has been the subject of a series of studies by Crozier and Pincus (see Munn, 1950, pp. 44 if., for a review of this work, and the controversy over the nature of the behaviour observed). The main papers of psychogenetic interest are Crozier and Pincus, 1931-2a, 1931-2b, 1931-2c, 1935, 1936. They found that different strains of rats varied in the angle taken up on the inclined plane in response to variations in the angle from the horizontal of the plane itself. Crosses between two of the strains were bred, and backcrosses made to each parental line in turn. The F₁ showed a pattern of geotropic behaviour which was interpreted as hybrid vigour (heterosis) affecting the rear limbs only and giving disproportionate development. The absence of this in the geotropic behaviour of adults of the cross was taken as confirming the hypothesis. Separate consideration is given to each back-cross (Crozier and Pincus, 1931-2c, 1936), and despite the very small numbers used it is claimed that the dominance of the genes from one strain can be shown.

Herter (1936) found that strains of mice differed in their preferred floor temperature. By means of Fi’s and backcrosses to a wild strain he was able to identify the important determining factor as the density of the belly fur (Herter, 1938; Herter and Sgonina, 1938).

While observations relating to differences between strains of unspecified degrees of genetical purity are still encountered (Schaefer, 1959; Myers, 1959), the post-World War II work on the inheritance of behaviour has concentrated on the use of the inbred strains of rats, and, more especially, mice, which are now available (Staats, 1958). The volume of work on these two species allows a consideration of it topic by topic.

The hereditary determinants of audiogenic seizures have been investigated by several workers; their findings are reviewed by Finger (1947) and Bevan (1955). An hypothesis of multifactorial genetical control seems to fit the experimental data rather better than those suggesting one- or two-gene action.

Strain differences in respect of the hoarding of food by mice were found by Smith and Powell (1955), and confirmed for rats by Stamm (1954, 1955) who attempted a genetical analysis using three pure-bred lines of different coat-colours. He obtained an F₁ from two of the strains and backcrossed to only one of them (1956). The results did not enable him to specify a genetical mechanism for the hereditary effects disclosed.

The influence of inheritance on emotional responses in five strains of rats, which included the three used by Stamm, was confirmed by Broadhurst (1958b), and these findings will be discussed in Chapter 4. Lindzey (1951) had previously shown the same effect with five inbred strains of mice.

Such strains of mice (Carter et al. mult., 1952) have been used with good effect in the study of activity. Thompson’s paper (1953b), employing fifteen of them in three behavioural situations, set a new standard in this field. He went on to confirm the findings on exploratory activity in five strains (1956), two of which had not been used in the previous study. A suggestive parallel exists between Thompson’s ordering of these strains in activity and that determined by the thyroid output measured in some of them (Amin, Chai, and Reineke, 1957). The relationship suggests that the higher the output the greater the amount of exploration. The genetical analysis proceeded with the breeding of Fi’s (Thompson, 1954), F₂’s and backcrosses to the two showing the highest and the lowest activity (Thompson and Fuller, 1957, 1960). This is the most complete analysis of this trait yet reported, and the results are of extreme interest. The heritability, or ‘nature/nurture ratio’, a measure of the extent to which the character observed is under genetical control, gives a value around 60%, the rest being non-genetical or environmental. An estimate of the number of genes involved is four or more, and there is some suggestion of dominance for those determining higher activity. The use of two somewhat different situations for measuring the activity allows the additional conclusion that the description of a genetical mechanism is in part dependent upon the way it is measured.

McClearn (1959) has also investigated the psychogenetics of exploratory activity in the mouse, on a somewhat broader basis, using four different tests of exploratory behaviour in novel situations, and six mouse strains. Thompson’s earlier findings were supported, and an cross of the two extreme strains, though not, unfortunately, the same strains as in Thompson and Fuller’s study, gave results which suggested that the trait as measured is determined multifactorially. The question of exploratory activity in the rat will receive further attention later; that it...

Table of contents

• Cover
• Title
• Copyright
• Original Title
• Original Copyright
• CONTENTS
• Editor’s Introduction
• PART ONE: EXPERIMENTS IN PSYCHOGENETICS Applications of Biometrical Genetics to the Inheritance of Behaviour
• PART TWO: EXPERIMENTS IN PSYCHOPHARMACOLOGY
• Bibliography and Author Index
• Subject Index