Our starting point was Franz Alexander's well-known hypothesis about the hypertensive personality. According to Alexander (1939), hypertensive patients are characterized by a neurotic conflict between passive dependent tendencies and over-compensatory, competitive, hostile impulses. Hypertensive patients seem to be anti-aggressive, submissive, polite, and reserved. At the same time, they show no direct neurotic symptoms such as anxiety, obsessive ideas, or conversion symptoms. Hypertension may be looked upon as a substitute for symptom neurosis. According to Alexander, hypertensive patients are unable to express freely aggressive impulses, and at the same time unable to repress or absorb the impulses through symptom formation. An accumulation of psychic energy takes place, which manifests itself in constant vasomotoric stimulation. In the long run, this development may be able to change the balance of the baroceptors and finally destroy the circulatory system.

A sample of MZ twins is particularly suitable for studying the influence of inhibited aggression on blood pressure. In addition to the methodological advantages of controlling the genetic and external environmental factors of childhood, one frequently finds a casting of roles with one of the twins dominant and aggressive, and the other as a submissive and timid partner.

In an earlier study (Wilde, 1964) on 88 MZ and 42 DZ twin pairs in Holland, DZ pairs, who had been separated for a minimum of five years, were compared with DZ twins living together on measures of neuroticism, extraversion, test-taking attitude and masculinity/femininity. The striking observation was made that separated DZ twins were systematically more similar than DZ twins living together across all personality traits concerned. No such difference was found between MZ pairs living together and MZ pairs living separately. In order to account for these findings, the hypothesis was put forward that the persons in the direct environment of a twin pair have certain behavioural expectancies with regard to the twin members, which depend upon the observation whether the twins are MZ or DZ. As soon as the twin pairs leave the parental home these behavioural expectancies come to a halt and the “true personalities” of the twins will emerge. This might explain why DZ pairs were found to be more similar after separation, and this reasoning also shows that it is inadequate to say that “the environment is the same” or “the environment is different”, without specifying which environmental variable is the same and which one is not. In some respects the environments of separated DZ pairs may have been more similar than the environments of DZ pairs living together.

As you all know, there is a growing concern with the Negro problem in America. I will look at one small aspect of that problem today: the possible hereditary difference in ability between Negro and White.

Fig. 1 is just one of many examples that could be chosen. It shows the extent of such differences in ability for different years, for male and female separately, between Negro and White students admitted to the University of Georgia, as reported by Hills (cf. Stanley and Porter, 1967). Ability was measured by the verbal score on the Scholastic Aptitude Test — a test widely used by college admission officers in the USA for selection of students.

Fig. 2 shows a comparison of the fertility of Negroes and Whites, indicating that less able Negroes have the highest fertility, while more able ones have lower fertility (Bogue, 1969).

Should the combined effect of these two factors (i.e., lower IQ,'s and greater fertility of low IQ, Negroes) lead us to worry about a gradual decline of the national level of intelligence in the USA? I believe not, and I will present some evidence which supports the thesis that the observed lower intelligence in US Negroes is due to an interaction between innate potential and unfavorable environmental conditions. If, as I believe, social conditions for the Negro are improving and if their greater fertility will level off as social conditions improve, we will not need to be concerned about a national decline in ability.

L'uso della cinematografia nello studio delle reazioni comportamentali è stato applicato da diversi autori. Definito da Gesell (1952) «cinemanalisi», tale metodo è stato dallo stesso autore proposto per uno studio metodico del comportamento dei gemelli. Successivamente, Splinder (1955) impiegò la cinematografia per uno studio sul comportamento globale di otto coppie gemellari MZ e quattro coppie DZ, mentre Freedman (1961) la utilizzò nella diagnosi di zigotismo. Infine, Gedda e Neroni (1955) — considerando la cinematografia quale mezzo tecnico di ricerca, in quanto causa di determinate reazioni — sottoposero 56 coppie di gemelli alla visione di film umoristici ed ansiogeni, riprendendone le reazioni posturali e mimiche.

Considerando che, oltre a permettere l'osservazione del comportamento nella sua dinamica globale, esso ne consente l'analisi nelle sue frazioni istantanee (1/24 di sec), il metodo cinematografico è stato da noi utilizzato per un'analisi del movimento. Nel presente lavoro riferiamo le nostre osservazioni sull'analisi del gesto del disegnare. Poiché questo gesto si può considerare prevalentemente condizionato dall'educazione e dall'ambiente culturale, abbiamo ritenuto che l'eventuale dimostrazione di una seppur minima componente ereditaria assumesse un particolare significato.

La misura del tempo è un dato indispensabile per la comprensione dei processi fisiologici e, nel nostro caso, più propriamente psico-neurofisiologici.

Uno degli aspetti più evidenti della variabilità dei tempi psicofisiologici è dato dall'esistenza di una variabilità dei sistemi operativi nel porre in atto la risposta individuale a stimoli ambientali.

Definiti come « intervallo minimo di tempo tra uno stimolo dato e una risposta volontaria », i tempi di reazione occupano un posto particolare tra i vari sistemi operativi, per la possibilità di standardizzazione delle condizioni sperimentali, di ripetibilità, di confrontabilità dei risultati e di adattabilità, mediante il cambiamento degli stimoli e delle reazioni, a un notevole numero di funzioni psicofisiologiche complesse.

I lavori sperimentali realizzati per identificare i fattori causali della variabilità dei tempi di reazione non hanno condotto finora a risultati apprezzabili, in quanto tutti i ricercatori hanno utilizzato l'analisi fattoriale, con il risultato che le stime delle singole componenti causali sono state variabilmente esaltate o diminuite.

This report deals with the nature-nurture problem in relation to some primary aspects of character in normal twins and siblings; namely, on 12 primary impulses, or propensities, whereon reports of detailed study are rare. These factors form the energetic side of any human being's behavior and thereby the native equipment in anybody's character: its units of composition. In agreement with Galton's dichotomy of intellect and character, the latter actually makes up the second half of our personality's organization: its motor area.

In the search for character roots through the interaction of heredity and environment, Galton was the first to bring out, through pedigree studies, the existence of noticeable hereditary components. However, as to inquiries by twin method, character is in a far less satisfactory status than any of the other heritable traits of personality. So far, we know neither the possible genetic stability of those primary impulses which in clinical experience passed for the most forcible, nor the degree of peristatic plasticity of those which might admittedly be the most docile.

A sample of 44 MZ and 41 same-sexed DZ twin pairs and 39 pairs of siblings were administered a standard battery of 120 questions of the Self-Rating Questionnaire type. For each pair, individual scores, as well as intrageminal differences, were worked out.

Although the heritability of general intelligence has been the subject of much study and can be considered to be well established, the heritability of specific factors in intellectual functioning has not as yet been the object of such intense scientific inquiry.

The recent work of Nichols (1965), utilizing a large sample of twins from the National Merit Scholarship testing program and employing a battery of tests measuring achievement in five different academic areas, is an excellent pioneering study. Nichols used a composite score derived from the five subtests, presuming this to be a measure of general ability, and he found that MZ twins were much more alike than DZ twins with respect to the composite score; about 70% of the variance in the composite could be attributed to heredity. The novel result of his investigation is his discovery that the specific subject areas also have significant heritability components. When the influence of the composite general ability upon subtests was removed statistically, the residual subtest scores also showed considerable heritability.

A limitation of Nichols' findings is that the subtests do not offer any potential theoretical link to basic factors in mental functioning. Such measures, however, may be provided by the fundamental factor analytic explorations of Guilford and his associates during the past twenty years. Since our own interest has been in the area of creative thinking and esthetic judgment, we have restricted ourselves in the present investigation to the use of tests in those areas whose factorial classification has been studied previously.

Our Section in Bethesda is primarily engaged in studies of schizophrenia and personality formation. I will summarize a number of our ongoing studies, and then briefly focus on a methodological issue: the possibility of twin studies moving beyond their heretofore almost constant, very useful tie to genetic studies.

We have previously reported an elaborate multidisciplinary study of a series of MZ twins discordant for schizophrenia, a smaller number of appropriately matched control twin pairs, and their families, aimed at studying nongenetic factors in the pathogenesis of schizophrenia (Pollin et al, 1965, 1966). We have described three interacting groups of variables which consistently differentiated the schizophrenic and nonschizophrenic twins in the discordant pairs (Pollin and Stabenau, 1965). These included an initial set of nongenetic constitutional differences, including birth size, vigor, and physiological competence; consequent different parental perceptions of, and relationships to, each of the twins in a given pair; and subsequent biological and life history differences, based on evolving personality differences, such as in fearfulness, competence, independence, initiative and the like, differentiating the schizophrenic index and the nonschizophrenic cotwins.

Studies have clearly established that the concordance rate for schizophrenia is much higher in MZ than DZ twins. Beyond this, it is difficult to generalize the findings to singletons. Analyzing the reports of MZ twins discordant for schizophrenia, Stabenau and Pollin (1967) view the differences between the index case and his nonschizophrenic cotwin, as stemming from an early biological defect or immaturity, which, in interaction with parental handling and other environmental response, may lead to socio-psychological incompetency and, in turn, to gross schizophrenic symptomatology.

In a previous study (Pollack et al, 1966), comparing schizophrenic patients and their nonschizophrenic sibs, we found that patients showed significant psychological (social and personality) deviations from the preschool age through adolescence. We did not obtain significant differences on the biological and very early developmental variables that clearly distinguished the discordant twins. These include birth weight, paranatal complications or motor development, such as age of walking. In contrast, Lane and Albee (1966) found schizophrenic index cases to be lighter at birth than their sibs, confirming the finding for twins. The clinical significance of this difference is debatable, since the index cases did not differ from national norms.

Over the past six years the Section on Twin and Sibling Studies, NIMH, has conducted intensive studies of 16 families with MZ twins discordant for schizophrenia. In addition, 3 families in which both twins were schizophrenic and 4 with no known psychiatric illness have been similarly investigated.

Each family is admitted to the Clinical Center, NIH, for two weeks of multi-disciplinary investigation. In the hope of shedding light on the question of neurologic findings in schizophrenic patients and their role in this disorder, detailed neurological examinations are performed on the twins by two neurologists. Patients with gross neurologic disturbance are screened out by our selection criteria. The examiners are therefore explicitly seeking minor deviations in neurologic status, rather than patterns of symptoms and signs leading to a specific neurologic diagnosis. Given this context, the neurologists recorded substantial numbers of signs. Yet, in none of the twins was there sufficient evidence to warrant a neurologic diagnosis.

The pairs of neurologic reports were subjected to a variety of procedures, in an attempt to quantify the results. For example, 11 of the first 13 index schizophrenic twins, as compared with 1 of 13 cotwin controls, were rated as having “probable” or “definite” neurologic abnormality, based upon the senior author's analysis of the number and type of signs recorded and the degree of agreement between the examiners. Significant group differences on number of signs reported were found between schizophrenics and nonschizophrenics, schizophrenic indexes and their cotwin controls, and schizophrenics and normals. In contrast, there were no significant group differences in the number of signs found between the nonschizophrenic cotwin controls and the normal twins.

Suicide is a complex problem and a phenomenon of mankind which is obviously influenced by a multitude of ethnological, socio-cultural, psychological and various other factors.

That a man takes his own life does not necessarily mean that he was mentally abnormal. On the other hand, it is a well established fact that the frequency of mental illness — affective disorders in particular — is high among suicides, and that one in six patients suffering from manic-depressive psychosis will commit suicide (Sainsbury, 1968). A family history of suicide is not quite uncommon, and beforehand one cannot exclude the possibility that somehow genetic factors may play a part in suicide; but evidence in favour of such an assumption seems to be scanty.

A survey of the literature reveals that there have been very few twin studies of suicide, and so far concordance in MZ twins seems to have been reported in three cases only.

The first case was observed, already in 1812, by a Dr. Stephens Williams from Massachusetts. He described twin brothers, presumably MZ, who both were captains and had distinguished themselves in the War of Independence. One of the twins settled down in the beautiful state of Vermont, whereas the other remained in Springfield. For several years, they continued to live apart, until, within short interval, they both committed suicide by cutting their throat. Williams points out that the mother and two siblings of the twins had presented symptoms of mental illness, and that, prior to their death, both had been in a state of melancholy, probably an endogenous depression.

In this preliminary report, which is part of a wider and more detailed study still in progress, I am reporting mainly the twins' mental state and associated physical abnormalities. For this purpose, I am surveying all the 2442 long-stay patients admitted during 30 years (1 September 1938-31 August 1968) to the Stoke Park Hospital Group, Bristol, which provides 1800 beds for mentally retarded patients of both sexes and of all ages. The survey's sample is shown in Tab. I.

In 1941, I published a psychiatric study of 69 same-sexed pairs of twins. The index cases were derived from 8596 consecutive admissions to three mental hospitals and one psychiatric unit of a general hospital in South Sweden, every patient being checked for twin birth in the official birth registers. There was no pair with more than one index case. Upon examination, 21 pairs were considered more or less certainly MZ, and 48 DZ. The degree of certainty of the zygosity diagnosis was expressed by a special formula (Essen-Möller, 1941b).

Of the 21 index cases, 7 (N. 1-7 of the monograph) were at that time judged schizophrenic. The later course revaled that one more index case (N. 12) was a schizophrenic and should have been included into this diagnostic group, which I shall have to concentrate upon in this brief presentation.

Out of the 8 cotwins of the schizophrenic index cases, 5 had presented symptoms of mental disorder up to the time of my investigation, which took place almost thirty years ago. This corresponds so far to a concordance rate of 62%. However, all of the cotwin disorders were relatively mild and transient in nature and consisted mainly of depressive or anxiety states. Even if some of the disordered cotwins had spent some time in a nursing home or in a psychiatric ward of a general hospital, none of them had been admitted to a mental hospital. And, although several of the clinical pictures contained some single trait suggestive of schizophrenia — such as ideas of reference (N. 2 and 7) or hallucinations (N. 5) — in no case a proper diagnosis of schizophrenia could be made. The cotwin who came closest to this diagnosis was a man aged 35 (N. 1), who gave much thought to telepathic phenomena and the like; yet, he was comparatively open-minded and accessible to discussion of his ideas, and he had never been incapacitated by them. Thus, at the time of the first investigation, the correct rate of concordance for schizophrenia in fact was zero. This finding was the more striking as the two other samples published up to that time, those of Luxenburger (1928) and Rosanoff (1934), showed rates of concordance at about 70%, although Luxenburger (1934) later corrected his figure to 33%, for diagnostic reasons. Personally, I was inclined to attribute my zero finding to chance, the number of pairs being small, and also to the relatively short time of observation.

Numerosi autori (Lo, 1967; Sakai, 1967; Balestra e Lanzara, 1968; Rosenberg, 1967, 1968, 1969; Goodwin et al, 1969) hanno di recente ripreso il tema dei rapporti tra psiconevrosi ossessiva e psicosi schizofrenica, giungendo a conclusioni pres-soché concordi sulla relazione che intercorre tra le due forme mentali, anche se discordi sulle percentuali (Lo 2.3%, Müller 12%).

Dal punto di vista genetistico, viene riconosciuto alla psiconevrosi ossessiva — sin dal Janet che la descrisse nel 1903 — un terreno ereditario, non sempre specifico ma polimorfo, condizionante l'instaurarsi e l'evolversi della sintomatologia coatta. Lowenfeld (1904), Luxenburger (1930), Lewis (1936), Brown (1942), Rüdin (1953), Balslev-Olesen e Jörgensen (1959), Bertuccelli e Schiller (1964), Rosenberg (1967), Lo (1967), Sakai (1967) ed altri hanno tutti confermato l'eredità della psicopatologia, seppure con differenti valutazioni e deduzioni.

Lo studio dei gemelli — benché povero di casistiche numerose, data la bassa frequenza popolazionistica della sindrome (5: 1 000 000, secondo Woodruff e Pitts, 1964) — ha portato un ulteriore contributo agli studi accennati (Tarozzi, 1938; Rüdin, 1953; Parker 1964; Woodruff, 1964; Inouye, 1965).

The results of the small number of existing investigations of criminality among twins have mostly been considered as contributions to the discussion of the relative importance of heredity and environment. I attempt to look at the problem in a slightly different context, but find it useful to give a brief summary of the older investigations. The results of previous studies utilizing the twin method to throw light on the problem of crime appear from Tab. I.

I am sure you will remember Lange's conclusion from 1929: “ As far as crime is concerned, MZ twins on the whole react in a definitely similar manner, DZ twins behave quite differently. In accordance with the significance of the twin method we must conclude that innate tendencies play a preponderant part among the causes of crime”.

There is one fundamental assumption behind the conclusions about the heredity of criminal behaviour, which is not fulfilled. The environment of each of the two twins in a pair must be equally similar or equally different, irrespective of zygosity. However, the milieus of the cotwins in a DZ pair are in fact more different than in a MZ one.

The Danish study is carried out in cooperation with the Danish Twin Register (Harvald and Hauge, 1965). The material consists of data about nearly 6000 pairs of twins, i. e., all twins born on the Danish islands in 1881-1910, where both twins have survived to the age of at least 15 years. The source material may be considered complete. About 900 pairs have been entered into the Central Police Register and/or into the local penal registers.

Negli ultimi anni, gli studi gemellari si sono orientati su nuove direttive di ricerca, nel tentativo di spiegare le cause delle oscillazioni di concordanza e il significato delle differenze sintomatologiche nelle coppie MZ affette da schizofrenia (Kringlen, 1964; Pollin e Stabenau, 1966; Gottesman e Shields, 1966; Tienari, 1966).

La spiegazione è di certo complessa, spesso ancorata al dualismo eredità-ambiente che tuttora divide gli psichiatri, ma ancor più spesso subordinata a cause teoriche ed empiriche inerenti alia materia e al materiale di studio. Prima tra tutte, il criterio nosografico della schizofrenia, ancora non delimitata dalle altre malattie psichiche (teorie quantitative di Bleuler, Kretschmer, Meyer, etc.), oppure nettamente differenziata nelle sue varietà cliniche (teorie qualitative di Jaspers, Kleist, Leon-hard, etc.). II concetto unitario si contrappone a quello dualistico che delimita ezio-logicamente le differenti forme tipiche e atipiche.

Una seconda fonte di errori risiede nella metodologia di ricerca, che negli studi gemellari si complica per la scarsa disponibilità di materiale, per la sua dispersione, per la difficoltà di seguire parallelamente i due gemelli nel multiforme decorso della malattia, nelle sue variazioni nel tempo, nell'età, nel contesto socioculturale, etc. Infime, non è da trascurare l'impostazione soggettiva del ricercatore (da cui nessuno sfugge), che porta involontariamente ad un pensiero autistico, condizionante la soluzione di un dubbio.

Uno studio genetico dell'epatite virale (soprattutto quella da virus A, o epidemica) appare, fra l'altro, giustificato (1) dalle anomalie epidemiologiche dell'affezione e dalla difficoltà di interpretarne le ripetizioni familiari, soprattutto a grandi intervalli di tempo e di luogo; (2) dalla notevole variabilità della risposta clinica all'agente, il che fa sospettare un'influenza del genotipo dell'ospite (Di Raimondo, 1962; Varay e Berthelot, 1969); (3) dalla presenza di particolari reazioni immunitarie (di tipo autoanticorpale), specie nelle forme cronicizzate e nella cosiddetta epatite cronica attiva, verosimilmente dovute a meccanismi genetici (Varay e Berthelot, 1969).

Abbiamo dunque condotto, su circa 1800 casi ricoverati nel 1967-1969 nell'Ospedale Spallanzani, oltre all'analisi delle aggregazioni familiari, lo studio particolare di coppie gemellari MZ e DZ, utilizzando anche casi registrati nella gemelloteca dell'Istituto Mendel.

L'indagine gemellare si basa finora su 29 coppie, con dati completi per 24, incompleti per 5. I parametri di malattia sono stati scelti con particolare riguardo al fattore tempo, inserendo così lo studio nel più vasto programma dell'Istituto Mendel sul «chronon» (Gedda e Brenci, 1969).

L'accostamento di tipo clinico-gemellare appare più interessante del semplice raffronto interzigotico, perché consente, tra l'altro, conclusioni sicure anche su poche coppie concordanti.

The Danish Twin Register, which comprises all twins born in Denmark between 1870 and 1920, has been used for studies of selected problems in the field of epidemiology and public health. This report gives a survey of the preliminary results of an investigation of this type, which intends to amplify the present knowledge about the possible harmful effects of smoking on health, by taking advantage of a twin material which makes it possible to keep the genetic factors under control.

A series of 762 MZ and same-sexed DZ twin pairs, which had their smoking habits mapped in 1959, has been followed continuously, and the mortality which has occurred in this group has been analysed in relation to tobacco consumption. Neither MZ nor DZ pairs showed any tendency to increased mortality in the heavier smoking cotwins. When the material was subdivided according to cause of death, no conspicuous exception from the general pattern was found, but the subgroups were relatively small.

The distribution of selected diseases and symptoms, mainly of the cardiovascular and respiratory systems, was studied in this and a second series, followed since 1966, with a total of 1584 pairs.

Precedenti ricerche popolazionistiche (Witkop-Oosternyk, 1957), genealogiche (Aycock, 1942) e gemellari (Herndon e Jennings, 1951; Masini, 1953; Rainero e Terragna, 1959; Di Raimondo e Pedone, 1964) hanno portato dati consistenti a favore dell'ipotesi di un'influenza del genotipo dell'ospite nel trasformare la semplice infezione da virus polio in malattia paralitica. Rimangono aperti, tuttavia, molti problemi riguardanti la reale estensione e le modalità operative, cioè, la fenogenesi, di un tale condizionamento genetico.

È dunque parso utile portare un contributo personale con un'analisi — condotta parallelamente in coppie di consanguinei, a livello qualitativo (presenza), quantitativo (entità) e cronologico (tempo) — delle fasi acuta ed evolutiva della malattia.

Sono state studiate 71 coppie consanguinee di poliomielitici (43 coppie di gemelli, 19 di fratelli, 2 di cugini, 2 padre-figlio, 2 zia-nipote), per alcune delle quali soltanto è stato possibile condurre un sufficiente studio longitudinale.

Esaminando, in questa sede, le sole coppie gemellari, osserviamo, soprattutto per la classe MZ, una notevole concordanza, a livello sia quali-quantitativo che temporale, come risulta dai seguenti esempi.

A new method of cross-sectional twin sampling from a population may be used in countries where authorities utilize electronic data processing of National Register data.

In Denmark, all National Register data are collected on magnetic tape. In January 1969 it was consequently possible, by the help of a 360-COBOL programme, to select all individuals in the Copenhagen area with identical birthday, month and year, and identical address. The selection was limited to the years 1943 to 1968.

Data from every person were tested against data from all other persons, to prove whether the person had one or more partners with identical data, i. e., twin, triplet, or quadruplet partners. Names and current addresses of the twins were written on self-adhesive labels intended for later correspondence. Had it been desirable, the computer might have produced, in the same operation, index cards and questionnaires ready for mailing. In the primary sample, a few “false” twin pairs from great collective housekeepings (as, for example, colleges) were included. These “false” pairs were excluded after comparing the partners surnames.

From the total population of 1 712 000 people, 4595 twin, 25 triplet, and 1 quadruplet sets were found. As many as 3754 twin pairs were born in 1951-1967. Of these, 34.68% were of opposite sex. Of the remaining pairs, 642 were born in 1943-1950, 28.19% being of opposite sex.