The XYY karyotype and criminality: A review

J.psychiat. Res.,1970,Vol. 7, pp. 153-170.Pergamon Press. Printedin GreatBritain.

THE XYY KARYOTYPE

AND CRIMINALITY:

SEYMOUR KESSLER

Department

of Psychiatry,

A REVIEW

and RUDOLF H. Moos

Stanford University School of Medicine, California 94305, U.S.A.

Stanford,

(Received 23 April 1969) (Revised 7 July 1969)

CRIMINALITY

was once thought to be the result of demonic or supernatural forces. Beginning with the eighteenth century, attempts were made to attribute criminal behavior to certain physical characteristics of the individual. Gall and Spurzheim, for example, attempted to associate various bumps on the head with specific personality traits. In Italy, Cesare Lombroso, and in the United States Ernest Hooton, argued that criminal behavior reflected an ativistic level of biological organization which had its concomitants in certain physical stigmata or anthropometric ‘marks of inferiority’.1 More recently, SHELDON,~ S. and E. GLUECK,~ and others4 have reported a relationship between criminality and bodily physique. The contribution of genetic factors to the production of criminal behavior is expressed in the concept of ‘bad seed’ and is explicit in the studies of SIR FRANCIS GALTON~ and of the Jukes and Kallikak families by DUGDALE~ and GODDARD’ respectively. Attempts at estimating the hereditary contribution to criminal behavior have been made by means of twin studies.8 But, the confounding of common genotypic and experiential factors among twin pairs make these studies difficult to interpret. In recent years fresh interest in possible genotypic contributions to criminal behavior has arisen due to the finding of a relatively large number of individuals with various chromosomal abnormalities in maximum security institutions for the mentally ill, the mentally subnormal, and among prison populations. Several recent crimes of violence perpetrated by individuals who subsequently were shown to have an abnormal chromosomal constitution have also received wide notoriety. Two specific cases stand out. In. both, the grounds for the defense rested heavily on arguments of legal irresponsibility resulting from the fact that the defendant carried a 47,XYY* karyotype. In France, Daniel Hugon was convicted of murdering a prostitute. During the course of his trial a special commission was appointed by the court to testify on the possible contribution of the chromosomal abnormality to the crime. The jury, apparently allowing for extenuating circumstances, decided on a somewhat lesser penalty than usual for this type of crime. In Australia, Lawrence E. Hammell was acquitted of murder on the grounds that he was legally insane at the time of the crime. According to newspaper accounts,10 the * The nomenclature is that established refer to this karyotype only as XYY.

at the Chicago Conference,

153

1966.9 In further citations,

we will

154

SEYMOUR KESSLERANDRUDOLFH. Moos

defense relied solely on the testimony of a prison psychiatrist who stated that ‘every cell in . . . (the defendant’s) . . . brain is abnormal’. Despite frequent warning+-17 against reaching premature conclusions, there has been a growing tendency to characterize XYY individuals as a unique group of uncontrollably aggressive psychopaths. This characterization has important legal, medical, psychiatric and social implications which need to be fully explored. This paper will review the evidence regarding the XYY syndrome to ascertain the extent to which XYY individuals differ from normal 46,XY males, will focus on a number of issues which are particularly important in interpreting the relevant studies and will provide possible guidelines for future research. The frequency of XYY individuals in the general population is not known for certain. On theoretical grounds, COURT BROWN1s has argued that the incidence of XYY individuals among liveborn males must be lower than that known for 47,XXY individuals. His argument follows from the fact that the chromosomal nondisjunctional event leading to a 47,XXY zygote could occur in either parent whereas that leading to an XYY zygote occurs only in the male parent. The incidence of 47,XXY individuals is believed to be between 1.318 and 2.21g per 1,000 live male births. On the assumption that chromosomal nondisjunction during gametogenesis occurs with equal probability in both female and male parents, COURT BROWNIE has estimated the incidence of XYY individuals as 1 per 1,000 live male births. Actual chromosomal surveys of newborn populations have revealed an incidence of XYY males ranging from 1 in 25020 to 1 in 1,lOO.ls The first instance of an XYY individual was reported by SANDBERGet al.21 and described in detail by HAUSCHKA et al.22 The man in question was detected because of the presence of mongolism and other congenital anomalies among his progeny. He was 6 ft tall, 44 yr of age, without physical defects, of’average intelligence, and the father of seven living children from two marriages. He was not a criminal. BALODIMOSet aZ.23review the literature with respect to the 12 known XYY cases detected to 1965; the majority of these cases suffered from various physical abnormalities. One of the first reports of a possible association between an extra Y chromosome and aggressive behavior came from a survey conducted in two British State Hospitals for patients requiring special security because of persistently violent or aggressive behavior.24 Among 942 male patients examined, 21 sex chromatin positive males were detected, a third of whom were found to have a 48,XXYY karyotype. Individuals with two X chromosomes, like normal females, usually show the presence of a densely staining sex chromatin body in cells of their buccal mucosa. In an attempt to ascertain whether an extra Y chromosome predisposes toward unusually aggressive behavior, first JACOBSet al.25 and then PRICE and WHAT’M~RE*~examined the chromosomes of almost all of the male patients in a maximum security State Hospital at Carstairs, Scotland; a total of 315 men. Nine cases of the XYY karyotype (2.9 per cent of the total group), more than half of whom were 6 feet or more in height, an&7 individuals with other chromosomal abnormalities were detected. CASEY et al.27 reported an unusually high frequency of XYY individuals among males 6 ft and over in height; 12 of 50 in a mentally subnormal group; 4 of 50 in a mentally ill group; and 2 of 24 in a criminal group. In a maximum security prison in Ohio, GOODMAN et aZ.14examined the chromosomes of 100 inmates greater or equal to 73 in. in height and found 2 XYY and 2 47,XXY individuals. GRIFFITHS and ZAREMBA*~surveyed 34 admissions to a British prison

THE XYY KARYO~PE AND CRIMINALITY:A REVIEW

155

at Wandsworth, 6 ft or more in height, and detected 2 XYY individuals and one with a 47,XXY karyotype. The examination of 33 other randomly selected prisoners admitted during the same period yielded one individual with a balanced translocation of the autosomes. In Melbourne, Australia, 3 XYY individuals and one 47,XYY/48,XYYY mosaic were found among a group of 34 prisoners greater or equal to 69 in. in height.29 Two of these individuals were convicted of murder and one of attempted murder. Chromosomal studies of 129 males greater or equal to 71 in. in height, in 4 different penal institutions in Pennsylvania, revealed 5 more XYY cases as well as 7 47,XXY onesa Surveys conducted in a number of different British institutions revealed 15 cases of XYY individuals, a majority of whom had engaged in criminal activity; several, however, showed no evidence of antisocial behavior.31 Examining 29 males in an approved school in England, ranging from 12 to 19 yr of age and with a height at or over the ninetieth percentile for their age, HUNTER~~ found 2 sex chromatin positive individuals and 3 with an XYY karyotype. The latter had all committed offenses against property. In a chromosome survey of 68 men, 70 or more inches in height, in a psychiatric hospital for the mentally subnormal one case showing a reciprocal translocation of the autosomes and 7 cases with sex chromosome abnormalities were found.33 Among these latter individuals, 2 had an XYY karyotype. A study of 204 consecutive admissions to a British prison resulted in the detection of 2 XYY males.a4 Chromosomal studies on 37 patients greater than 180 cm in height in an institution for psychologically abnormal criminals in Denmark revealed 2 additional cases.35 Both had been convicted for crimes of arson, among other offenses. AKESSON et al.36 studied 86 consecutive admissions of men 183 cm or more in height in two mental hospitals in Sweden and found 7 individuals with chromosomal abnormalities. Of these, 3 had an XYY karyotype and one was a 46,XY/47,XYY mosaic. One of the XYY patients had a criminal record. Screening 210 male patients 6 ft or more in height in 4 maximum security hospitals, DALY~~ found 10 XYY cases. Another case was detected among 32 tall males in hospitals for the mentally subnormal. Besides these cases, over 50 others have been detected in institutions or in private medical practice; COURT BROWNIE has comprehensively reviewed this literature. In Table 1, the studies concerning XYY individuals published subsequent to the Court Brown review and not enumerated above are shown. In sum, the evidence is impressive. In the relatively few years since the JACOBS et al.25 report, over 100 XYY individuals have been detected, many of whom have been involved in criminal and other antisocial activities. Studies of certain institutionalized populations have obtained frequencies of XYY individuals ranging from 1 in 3549 to 1 in 100,34 representing a possible 20-fold50 or greater increase over the newborn incidence. This might indicate that XYY individuals are predisposed to antisocial and criminal behavior and suggests that XYY individuals may differ significantly from chromosomally normal males with respect to behavioral and other characteristics. In the section that follows, the morphological, physiological and behavioral characteristics which are believed to be associated with XYY individuals will be examined.

height and behavior

2

1

BORGAONKAR, D. S., et al. (1968)42

THORBURN, M. J., et al.

4 1 0

1

1

SERGOVICH, F. R. (1968)20

FORSSMAN, H., et al. (1968)45

NIELSEN,J. (1968)46

WIENER,S. and SUTHERLAND, G. (1968)47

HASHI,N., et al. (1968)48

* At birth of index cases.

1

(1968)44

LISKER, R., et al.

detected by chance

41 patients in State Hospital, Denmark > 180 cm in height

newborn survey of 1066 males height

family study

(46,XY/47XYY mosaic) height and behavior

1

MATTHEWS,M. B. and BROOKS,P. W. (1968)41

(1968)4s

36 basketball players 2 71 in. in height

Basis for ascertainment

27

41

16

45

IQ 116 (Stanford-Binet)

no criminal record

22

19

43

31

P-R interval increased ; IQ 100 (WISC); hyperactive hypogonadism, orthopaedic abnormalities ; ECG normal ; mental retardation.

26

28

1 of3

lofl

120f12

49

26

1 2

2 of 2

Birth rank

30 32

Maternal Paternal age* age*

EEG normal; IQ 125 (WAIS)

personality disorder

undescended testis; retarded bone age ; sickle-cell trait ; abnormal EEG; aggressively destructive; possibly psychotic

Clinical and behavioral findings

ECG normal; EEG with nonspecific abnormalities; no behavioral disturbances; IQ 97 (Wechsler) 174.6 personality disorder; IQ 77

192

205

195

227

197

15 28

203

188

Height (cm)

31

23

I

Age (yr)

STUDIESPUBLISHED SINCECOURTBROWN’S~~ REVIEWOF THELITERATURE

0

1

N

XYY

GOODMAN,R. M., et al. (1968)40

PERGAMENT, E., et al. (1968)=

MINTZER,R., et al. (1968)38

Reference

TABLE 1.

B

F EI c p

5

1 P g

g 2

L Q\

THE XYY

157

KARYOTYPE AND CRIMINALITY: A REVIEW

MORPHOLOGICAL

CHARACTERISTICS

Height The outstanding morphological characteristic associated with XYY individuals is their height. In their original report JACOBS et aLz5 suggested that among the Carstairs group an individual more than 72 in. in height had an approximate 50 per cent chance of having an XYY karyotype. This estimate seems to have been somewhat high.4g Nevertheless, the mean height of the 9 XYY patients (181.2 cm) in the Carstairs study was significantly greater than the mean height of the 305 males (170.7 cm) with a single Y chromosome in the same institution. The 2 XYY males detected at the Grendon Prison, Great Britain, were 70 and 72 in. tall whereas 38 age-matched 46,XY controls averaged 69 f 2.4 in. in height.s4 In 22 adult XYY cases not ascertained on a basis of height, and for whom measurements are available, 10 are greater than or equal to 72 in. in height (Table 2). These data do seem to suggest that an extra Y chromosome is associated with increased height. However, some TABLE 2. Height (cm) 183 180.5 182 186 175 177 183 181 185.5 188 171 183.5 191 182 196 182 169 182 178 183 195 182

HEIGHTS OF ADULT XYY Age 44 23 18 31 32 39 17 31 28 34 22 28 64 26 39 52 17 38 22 34 45 41

MALESNOT IDENTIFIED ON THE BASISOF HEIGHT Reference

SANDBERG, A. A., et al.=’ COURT BROWN, W. M., et aks’ MONTERO, E. and DUR~N, I.52 PRICE. W. H.. et al.26 PRICE; W. H.; et aLz8 PRICE, W. H., et aLz6 PRICE. W. H.. et al.26 PRICE, W. H., et al.26 PRICE. W. H.. et aLz6 PRICE; W. H.; et aLz6 PRICE, W. H., et aLz6 PRICE, W. H., et aLz6 BALODIMOS, M. C., et aLz3 NIELSEN, J., et aLs3 WILTON, E. and LEVER, A.54 THOMPSON,H., et al.65(data COURTBROWN, COURT BROWN, W. M., et al.31 COURT BROWN, W. M., et aLsl BARTLETT, D. J., et aZ.34 BARTLETT, D. S., et a1.34 LISKER, R., et aLd4 WIENER, S. and SUTHERLAND,G.47:

in

1968)18

1961 1964 1965 1966 1966 1966 1966 1966 1966 1966 1966 1966 1966 1966 1966 1967 1968 1968 1968 1968 1968 1968

institutionalized XYY cases may have been drawn from families with an initial tendency toward tallness. In several cases chromosomally normal siblings of institutionalized XYY individuals were as or nearly as tall as their XYY brothers.e9@ The tallest XYY male reported so far measures 227 cm in height .4s In his family history it was noted that all his living sibs were tall and the father was said to be nearly as tall as the patient. HUNTER~~ also suggests the possibility that XYY individuals, ‘. . . because of their great height and build . . . present such a frightening picture that the court and psychiatrists would be biased to direct them to special hospitals for community safety’.

158

SEYMOUR KESSLER ANDRUDOLFH. Moos

Physical abnormalities Morphologically, XYY individuals display a variety of phenotypes ranging across a broad spectrum, from the normal to the abnormal. XYY individuals detected as children appear to show a high frequency of physical abnormalities, undescended testes commonly being found. Neck webbing, a symptom generally associated with Turner’s syndrome has been described in an XYY child57 and in two 45,X/47,XYY mosaic females.58,59 Two XYY children have been described as phenotypic females.60,sl Among the institutionalized adult cases, most seem to be free of genital anomalies, however, adult XYY cases with hypogonadism and other abnormalities have been described. CARAKUSHANSKYet al.62 review the literature regarding the association between the XYY karyotype and hypogonadism and/or dysplastic genitalia; a total of 13 cases. A phenotypic female adult originally described by FORSBERG et al. 63 has been diagnosed as an XYY by COURT BROWN.~* Several cases of individuals with supernumary Y chromosomes have been described with vascular abnormalities and varicose ulceration of the lower extremities.lQs~s4 THORBURN et aZ.43 speculate that the additional leg length associated with the increased stature of these individuals may lead to a poor supply of blood to the lower extremities and thus predispose to varicose ulceration. The presence of acne in 4 cases has been reported by TELFE?Ret aZ.30 although this characteristic is not mentioned as being associated with most of the other reported cases. The presence of facial acne is of interest because it may indicate an increased level of androgen production. PHYSIOLOGICAL

CHARACTERISTICS

EEG and neurological abnormalities FORSSMAN and HAMBART~~have suggested that antisocial behavior leading to inStitUtionalization may be due to brain dysfunction or damage (as reflected in an abnormal EEG). In the few instances where the EEG has been studied in XYY individuals, grossly abnormalF6 mildly abnormalsgJ@‘,ss and normal findings 15~1953have been reported. With respect to the institutionalized cases, no comparisons with matched controls have been undertaken and the incidence of EEG abnormalities among populations of institutionalized individuals is not known. BORGAONKAR et al.42 reported a case which had a normal EEG but which exhibited an abnormal EEG five years previously. This would indicate caution concerning any conclusions based on EEG data without thorough follow-up examinations. Neurological abnormalities, particularly intention tremors in the upper extremities, were found in 10 out of 12 XYY males associated, in general, with body asymmetries.37 Since all but one of these 12 individuals were institutionalized with various diagnoses of mental retardation or mental illness and no observations on matched chromosomally normal inmates were reported, it would be premature to conclude that these neurological abnormalities are related to the presence of an extra Y chromosome. Plasma and urinary testosterone The XYY case identified by WELCH et a1.G7revealed a plasma testosterone concentration more than four standard deviations from the mean of a sample of normal males investigated

THE XYY

KARYOTYPE AND CRIMINALITY: A REVIEW

159

in the same laboratory. Since the presence of testosterone is known to be associated with aggressive behavior69 elevated levels provide a possible mechanism through which the XYY karyotype might produce behavioral changes, possibly arising or being exacerbated at the time of puberty. The 2 XYY cases studied by GOODMAN et al.l* and the 3 cases studied by WEINER et aZ.,2Qhowever, all showed normal levels of plasma testosterone. GOODMANet ~1.14 cite an unpublished study by Migeon in which the plasma testosterone levels of 12 additional XYY cases were evaluated. Half showed elevated levels whereas the other half showed normal levels. ISMAIL et aZ.70 compared the mean 24-hour urinary testosterone output of 6 XYY patients in the Carstairs group to that of 19 presumably normal 46,XY ambulant males and found significant differences. The mean for the former group was Xl *I f 11 *Omg/24 hr whereas for the normal males it was 51.7 f 1.6 mg/24 hr. However, when the XYY individuals were compared to a group of I1 46,XY males in the Carstairs Hospital matched for age, height, and IQ, no significant differences in urinary testosterone levels were found. The mean for these 46,XY inmates was 69.2 f 9.1 mg/24 hr. RUDD et aZ.‘l studying a different group of XYY males and their fellow chromosomally normal inmates confirmed the findings of ISMAIL et al.70 and have suggested that changes in the mechanisms controlling the diurnal rhythmicity of testosterone levels may account for the elevated levels found in institutionalized males. Gonadotrophin excretion PAPANICOLAOU et aZ.72 studied gonadotrophic function in 3 XYY males, comparing urinary follicle stimulating hormone (FSH) and leuteinizing hormone (LH) levels to known published values for normal males. Serial FSH levels (14.56 f 1.54 I.V./24 hr) were within the normal range, but serial LH levels (77.34 f 16.6 I.V./24 hr) were elevated over that of the normal range. The absence of a comparable control group and the differences between the assay method employed by PAPANICOLAOU et a1.72 with that used to determine the standard values, make these data difficult to interpret. ECG PRICERSexamined the electrocardiograms of 20 XYY individuals (including 2 mosaics) and a control group of 28 institutionalized mentally subnormal 46,XY males comparable in age, intelligence and stature. In comparison to the control group, the XYY men tended to show a prolongation of the P-R interval. The mean (& S.D.) P-R interval in the former group was 0.155 f 0.021 set whereas in the XYY group it was 0.184 f 0,035 sec. The presence of secondary R waves in VI was found among 20 per cent of the XYY individuals and notching and reduction in the size of the S wave in VI was also frequently observed. Although prolonged cardiac conduction has been reported in other XYY individuals, normal electrocardiograms have also been reported.41~*3~*7~53 BEHAVIORAL CHARACTERISTICS Intelligence Of the approximately 50 cases which have been tested or evaluated with respect to intelligence, a broad spectrum of results have been shown ranging from grossly retarded to substantially above average. An I.Q. score of 125 has been found in one XYY male.42

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SEYMOURKESSLER ANDRUDOLFH. Moos

More than 35 of the cases have been evaluated as below average in intellectual functioning utilizing such divergent tests as the Wechsler-Bellevue, Wechsler Adult Intelligence Scale, Stanford-Binet and Raven Progressive Matrices. Since the vast majority of these cases have been identified in institutions for the mentally subnormal no conclusion about the relative intelligence of XYY males can be drawn. Furthermore, in studies which have used matched chromosomally normal controls, no significant differences between XYY and 46,XY males were found.34974 Other tests HOPE et al.74 compared 7 of the Carstairs XYY males with 11 matched controls. Tests measuring hostility, direction of hostility, reactive-narcissism, overactivity, dependence, hysteroid-obsessoid tendencies, speed of decision and social desirability response set were administered. The two groups were not different in tested hostility or in the direction of the expression of hostility, i.e. whether it was directed inwards against the self or outwards against others. The largest group differences were on reactive-narcissism and overactivity (controls scored higher) and dependence (XYY’s scored higher). The authors interpret these findings as indicating that the XYY males are ‘. . . rather lower in self-esteem than are the controls.’ Interestingly, the XYY’s were more obsessive or introverted (Eysenck Personality Inventory) and said that they were slower and more cautious in making decisions. BARTLETT et aZ.34 compared 5 individuals (2 XYY males, 2 47,XXY males, and one 46,XYY/47,XXY male) with 38 age matched controls. The individuals were tested with the Raven Progressive Matrices, the verbal reasoning part of the 16 P-F, the Eysenck Neuroticism and Extroversion Scales, the Anxiety battery of the IPAT and a hostility battery. No marked similarity of scores was found on any particular psychometric test for individuals of a given abnormal karyotype. The number of XYY males thus far tested is too small to suggest any consistent trends, however, the possibility of differences in self esteem and in the expression of hostility should be pursued. Criminality Working on the hypothesis that XYY males are more aggressive than their fellow prison inmates, WELCH et al.67 surveyed all the senior nonadministrative custodial officers at a Maryland institution for defective delinquents, who were requested to provide a confidential list of the 12 most aggressive, dangerous, or violent inmates. The lists were pooled and 10 of these prisoners were then examined to determine their karyotypes. All were chromosomally normal. BARTLETTet al.s4 compared the criminal records of 2 XYY male prisoners with 38 fellow XY inmates matched for age and found no significant differences. The crimes committed by the XYY individuals were primarily against property rather than the person. PRICE and WHATMORE’s compared the 9 Carstairs XYY individuals with 18 46,XY controls classified as having a severe personality disorder of undetermined cause. Seven of the 9 XYY individuals were detected in a wing of the institution for the mentally subnormal (East Wing), whereas 2 were found in a wing designed to house mentally ill indivi-

THE XYY

KARYOTYPEAND CRIMINALITY: A REVIEW

161

duals (West Wing). Among the mentally subnormal group, XYY individuals constituted 3.6 per cent of the total group whereas among the mentally ill population they constituted only 1.7 per cent of the total group. Thus, with respect to the two wings of the hospital, the XYY individuals do not seem to be randomly distributed. The control group, on the other hand, was randomly selected from among the entire chromosomally normal hospital population. With respect to matching for length of institutionalization, PRICE and WHATMORE’~ point out that 6 of the XYY group (2/3) had been admitted to the Carstairs Hospital before and 3 (l/3) since 1957, whereas 6 of the control group (l/3) had been admitted before and 12 (2/3) since that year. It might have been informative if comparisons of the two groups had been conducted in a double-blind fashion, on the basis of their location within the institution and with matching for length of institutionalization. The conclusions drawn from the Carstairs and similar studies may be summarized as follows : . (1) The penal against persons were for crimes victions among

records of the XYY individuals show significantly fewer crimes of violence than those of the controls (of a total of 92 convictions, only 8.7 per cent against a person in the XYY patients whereas out of a total of 210 conthe controls, 21.9 per cent were for crimes against the person).

(2) The manifestation of the disturbed behavior, as measured by the age at first conviction appears to be earlier in the XYY group than in the controls (a mean of 13.1 yr as against 18.0 yr in the controls). The age at first conviction ranges from 8 to 21 yr (median = 14 yr) among the XYY males and from 10 to 28 yr (median = 17 yr) among the controls. (3) In the families of the patients, the frequency of crime among siblings of the XYY individuals was significantly lower than among those of the controls (among the 3 1 siblings of the XYY cases, only one conviction was found, versus 139 convictions among 63 siblings of the controls). There is thus no predisposing familial environment to account for their criminal behavior ‘. . . and their criminal activities often start at an age before they are seriously influenced by factors from outside the homes’.75 (4) It is the behavior disorder antisocial activities.33,4g

rather

than intellectual

incompetence

that leads to their

(5) Repeated and prolonged attempts at rehabilitation and treatment of these individuals have not been successful.7” Several considerations seem to make these conclusions premature. First, with respect to the conclusion concerning the lack of familial predisposition to criminality, the same reasoning may be applied to 11 of the Carstairs 46,XY controls, since all of the convictions among the siblings of the control group were concentrated in only 7 out of the 18 families. Also, there are a variety of ways in which parents who are themselves not criminals may reinforce aggressive behavior in their children. For example, either the intermittent positive reinforcement of aggression or the punishment of aggression by parental aggression seem to lead toward greater aggression in children. 76 The effects of parental styles of discipline or socialization with regard to aggressive behavior have effects which can be seen very early in the child’s development.77 There is also considerable evidence to suggest that peer, school,

162

SEYMOUR KESSLER ANDRUDOLFH. Moos

and other influences outside the home make themselves prominently felt at a very early age.78 Second, with respect to the conclusion that it is the behavior ‘. . . disorder rather than the intellectual incompetence which prevents them from functioning adequately in society’,33 the close connections between emotional and intellectual development would appear to make if difficult and perhaps unnecessary to attempt to make this distinction. Several recent studies suggest initial cognitive and social cue determination of emotional states.79 Finally, the present stage of research in the area of evaluating the effects of hospitalization or institutionalization indicates that it is probably premature to suggest that repeated rehabilitative attempts with XYY males have been unsuccessful. Little is known about the differential effects of institutionalization in different populations. Furthermore, societal expectations of the repetition of crime, inherent in the philosophy of incarceration, may itself be a factor in promoting the repetition of criminal offenses and of making rehabilitation more difficult.80 Lastly, rehabilitative failure might suggest change in rehabilitative techniques rather than prediction of future failures. One important point stands out clearly in the Carstairs study; XYY individuals are not uncontrollably aggressive. Compared to their fellow 46,XY inmates, the XYY individuals appeared to be better adjusted to the institutional situation and most of the criminal offenses present in their preadmission histories involved crimes against property rather than the person. PRICE and WHATMORE~~ note that ‘ . . . the control patients are more openly hostile, and violently aggressive outbursts are more common’. Needless to say, XYY cases who show no evidence of abnormal or criminal behavior have been described22,2s~s1~4s147 suggesting that other genotypic and environmental factors are operative to generate the antisocial behavior attributed to the presence of an extra Y chromosome. On whatever basis comparisons have been made between XYY individuals and similarly institutionalized 46,XY males, no striking mean differences have been found in any morphological, physiological, or behavioral character. At best, certain morphological differences, e.g. height, are suggestive and require further study. XYY males do not appear to constitute a unique group within institutions when compared to their fellow 46,XY inmates nor to males with other chromosomal constitutions (e.g. 47,XXY and 48,XXYY) who also tend to be found in institutions at presumably high frequencies. Since the phenotypic expression found associated with XYY males is so heterogeneous, no conclusions concerning their ‘typical characteristics can be drawn at the present time.

METHODOLOGICAL

AND CONCEPTUAL

CONSIDERATIONS

In the next section, our major aim is to point out methodological and conceptual considerations which may be helpful in the interpretation of the current research and which may suggest alternative guidelines for future work. First, there are a number of important methodological issues. The criteria used in the evaluation of the Y chromosome and the number of cells counted to determine the karyotype vary considerably between laboratories making it difficult to ensure interlaboratory reliability. As the number of laboratories conducting karyotyping procedures grows, consideration of intra- and inter-laboratory reliability in the identification of chromosomal

THE 2XY

KARYO~PE AND CRIMINALITY: A REVIEW

163

abnormalities increases in importance. At a minimum, details should be provided in published studies concerning the criteria and the methodology employed to detect XYY individuals. There also seems to be a necessity for double-blind studies, i.e., studies in which the laboratory technician does not know anything about the group being investigated, and probably even more important, in which the investigators that do the clinical observations, history-taking and/or psychological evaluations do not know about the chromosomal constitution of their subjects. This consideration is particularly important in longitudinal studies of children detected at birth with chromosomal abnormalities. The possible operation of experimenter biassl makes this an essential point to consider. The full range of standard psychological assessment techniques should be utilized (in a double-blind fashion whenever an examiner is involved) in order to help test out various hypotheses relating the presence of an XYY karyotype to lower self esteem, to the necessity to defend against different psychological threats, etc. Clinical interview and psychological assessment procedures should both be utilized in group characterizations or comparisons wherever feasible. A greater use of different methods, both questionnaire and experimental, for the assessment of aggressive tendencies is also needed. In this connection the effect of refusal to cooperate in a study may be important, especially since refusal may be related to affiliative and aggressive or rebellious tendencies.sa*aa This was a particular problem in the study by HOPE et al.74 who were only able to test 7 of 9 XYY and 11 of 18 control males. Since many subjects will participate in some aspects of a study even if they refuse to participate in all aspects of it, comparisons between total groups on selected variables may be possible. The relevance of this problem is underscored by research indicating that there are important psychological differences between people who volunteer and who do not volunteer to participate in experiments.84 Another important issue relates to the characteristics which should be matched when XYY and control individuals are compared. If stature or intelligence are matched, then there clearly will be no between-group differences in these and in other linked variables. The complexity of this problem is illustrated by the fact that PRICE et al,26 PRICE and WHATMORET,‘~ and HOPE et al.74 utilized 3 different control groups for comparison with the same 9 XYY males. There is no one solution to this problem. However, the social class, length of institutionalization, and level of intellectual functioning of the groups should be matched since many variables have been demonstrated to vary with these factors. Since the number of XYY males identified in any one study is usually small it would be possible to adopt a strategy of utilizing multiple comparison groups each of which might be matched to the propositi on different variables. If the XYY males consistently differ from these multiple comparison groups on particular variables, it would suggest that these variables might be of unusual importance. A related question is whether there should be an age or height restriction on initial sample selection. Due to the complexity of the necessary chromosomal analyses and the low incidence of XYY individuals in the general population it seems reasonable to select from subpopulations of individuals who may have a relatively higher incidence of the abnormality in order to identify cases for further study. This sampling procedure makes it impossible to draw any conclusions about the relationship between height and the relative

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SEYMOURKESSLERAND RUDOLF H. Moos

incidence of XYY males in groups varying in height. i7 These conclusions can only be made on the basis of population studies which systematically sample the full range of height. The same considerations would apply to other variables as well. Second, without exact knowledge of the general population incidence of the XYY condition, the argument concerning the elevated frequency of these individuals in institutions has little meaning. But even if the frequency of XYY males in special security institutions is increased over the incidence level in the general population, it does not necessarily follow that they are more predisposed to behavior leading to institutionalization. For example, there may be important social class or other subpopulation group differences in the rate of chromosomal abnormalities. It has recently been suggested that sex chromosome anomalies may occur more frequently in families with a depressed socioeconomic status.s5 Should this finding be confirmed, it would clearly be necessary to ascertain whether the XYY males in institutions come largely from lower socioeconomic groups and whether the proportion of institutionalized XYY individuals from various subgroups exceed their relative proportions in the population subgroup. This consideration gains added importance because of the strong link between social class and violent or criminal behavior.a6,s7 It also underscores the need for further detailed population studies of sex chromosomal abnormalities. The characteristics of the populations investigated in these studies should be carefully identified. The evidence to date does not appear to corroborate the conclusion that XYY males are particularly aggressive. For example, COURT BROWN et al.31 discuss two cases who managed to maintain themselves at a low level in society without infringing the law until fairly late in life, and then the infringements were trivial. One case was charged with the theft of a milk bottle and shirt and was committed at age 37 while another was committed at age 61 after two charges of breach of the peace. These two cases raise the issue of the necessity of a careful prior definition of different classes of aggressive behavior. In most studies the only distinction has been that of crimes against people versus crimes against property. Further distinctions should be made in each of these areas. Even more importantly, more detail about the circumstances relating to the aggressive outburst are needed. For example, an individual who engaged in a partially peer-provoked attack might be more submissive, obedient, and needful of immediate peer rewards and less violent and rebellious than another who resists the pressure to engage in such an attack. It is also possible that what characterizes XYY males is a general tendency to react quickly and impulsively, which may manifest itself in a greater emotional variability or lability and a heightened tendency to act nonaggressively as well as aggressively (see, however, HOPE et aZ.74). If this were true it would suggest added importance for the role of stimulus cues and of the social environment in eliciting aggression rather than other reactions. COURT BROWNIE has suggested that there may be an alteration in the decision making process in XYY males. This raises the issue of altered brain functioning and possible altered information processing. It might thus be informative to study XYY and other chromosomal abnormalities utilizing evoked cortical potential** and related techniques. In this connection, the fruitfulness of the conceptualization that individuals are either aggressive or not aggressive has been called into question by several recent studies showing

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that consistent differences between situations and situation-by-person interactions account for as much or more of the variance in aggressive behavior as consistent differences between persons.8Q,90 A somewhat similar problem is raised by the conceptualization of different types of aggression. MOYER~~ has suggested that aggression is not a unitary phenomenon, and has tentatively listed several types; predatory, inter-male, fear-induced, irritable, territorial, maternal and instrumental. He suggests that these types may be classified on the basis of the stimulus situation which will elicit them and, most importantly, that each type has a particular neural and endocrine basis. This makes the careful study of the exact situation and type of aggressive behavior which occurs in the XYY males even more critical, since it raises the hypothesis that they may show only certain types of aggression with increased frequency. The possibility of differences in testosterone metabolism in XYY males should be further explored in order to uncover both possible biochemical mechanisms by which an extra Y chromosome might predispose an individual to react aggressively and to elucidate possible differential links to different types of aggressive behavior. Further knowledge concerning these mechanisms might suggest possibilities for their biochemical modification in the future. Third, the extent to which the possession of an XYY chromosomal constitution alters normal psychological development is important. In what types of circumstances might positive adaptive consequences ensue ? For example, if some XYY males tend to be taller and bigger than their peers they may be more likely to be attracted (on the basis of compatibilitysa or similarityg3) to and model or imitate other taller males. Thus they might be nurtured in an essentially altered psychological environment with a premium on physical activity and/or the expression of aggression. It is also possible that their tallness might set them apart from their peers,94 and that they might be more likely to experience isolation, loneliness, low self esteem and various frustrations possibly resulting, in turn, in increased shyness and withdrawal, anger and aggression, or other more deviant responses. On the other hand, it is possible that taller males might be more popular than average and might become leaders with high self esteem during their adolescent years. Thus, there are a number of very important psychological developments which could potentially be linked with increased height. The extent to which the overall results tend to be more or less adaptive will depend on a host of other variables ranging from the individual’s general level of intellectual functioning to the types of behaviors which are most likely to be rewarded in the social settings which the individual inhabits. Fourth, the phenotypic heterogeneity associated with the XYY karyotype needs to be clarified and explained. CARAKUSHANSKY et al.62 and HIENZ~~ suggest that the cases exhibiting physical abnormalities may represent a separate nosological entity distinct from those which are found in maximum security institutions, speculating that there may be qualitative differences in the duplicated genetic material in the two groups. Our present state of knowledge regarding the genes carried on the Y chromosome would make confirmation of this hypothesis difficult. The phenotypic heterogeneity found among XYY individuals may be due to several other mechanisms. FRANKS et aZ.“l suggest the possibility of an undetected 45,X/47,XYY

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mosaicism in some individuals, with possibly the regression of the 45,X cells and their replacement by a better-fitted XYY stem line. Mosaicism may result from anaphase lag or from nondisjunction during mitosis and would require the study of other tissues in addition to the peripheral blood leukocytes in order to .be detected.96 Positive findings prove that mosaicism is present, but negative findings do not necessarily prove that mosaicism is absent. Other possibilities are the modification of gene action on other chromosomesg7 or the reduction of the canalized or homeostatic properties of the genotype96 due to the presence of an extra chromosome, which may lead to phenotypic lability during development. Of course, it is also possible that the differences found among XYY individuals are simply due to the differential modes of their ascertainment. Fifth, there are some important questions relating to the comparisons between XYY males and individuals who have other types of chromosomal abnormalities. It has been suggested that 47,XXY individuals (Klinefelter’s syndrome) may be particularly prone to aggression and that there is also a greater proportion of such individuals in special security institutions than might be expected on the basis of their incidence in the general population.gg-iOa These data cast doubt on the hypothesis that it is particularly the extra Y chromosome which predisposes toward either aggressive behavior and/or institutionalization. Others have suggested that the presence of a second cell line may modify the effects of a 47,XYY line.31 The comparison of groups of cases with different types of chromosomal abnormalities in terms of the history of the development of different types of antisocial behavior might shed some light on whether there is any spedjk connection between an extra Y chromosome and increased probability of aggressive behavior. An alternative hypothesis would suggest that various types of chromosomal and resulting developmental abnormalities might each be linked with various types of psychological ‘deviancy’, including aggression-proneness. These points are made more intriguing by the finding of CLOSE et al.33 that whereas 2 of 19 individuals over 6 ft tall in an English hospital for mentally subnormal and psychiatric cases had an extra Y chromosome, 3 of these same 19 individuals had an extra X chromosome. Thus, XYY males may be taller than average, but so may individuals with an extra X chromosome.50 Lastly, there is a need to develop strategies for genetic counseling. VALENTINE and SERGOVICH~~ raise the important question of whether parents of XYY children detected in newborn surveys should be informed of that fact. Their strategy is, wisely, a conservative one; such information is withheld. The knowledge that their child is an XYY carrier may engender anxiety in the parents which in turn may lead to a disturbed familial relationship and expectation of antisocial behavior. Another problem requiring further study is the mechanism or mechanisms which produce the double Y condition. Meiotic nondisjunction is presumably the most probable route. Nevertheless, many questions remain to be answered. THOMPSON et al.55 studied a fertile XYY male who fathered a daughter and six sons, all normal. Since the chances of an XYY individual producing a son with a 46,XY karyotype is l/3, this pedigree is indeed notable. The authors suggest the possibility that selection towards chromosomally normal spermatocytes may occur in pre-meiotic stages. Finally, there is the possibility of increased risks of producing an XYY child with advanc-

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age. THORBURN et al.43 suggest that a paternal age effect may be operative. however, finds no association with paternal age. COURT BROWNSO has suggested that the association between the XYY karyotype and criminality may be the most outstanding discovery yet made by human cytogeneticists. The available evidence is too equivocal to state with certainty what effect these studies will have on human behavior genetics. It is clear, however, that the approaches used in the research to date have been inadequate to establish any strong correlation between the presence of an extra Y chromosome and specific patterns of behavior or with specific morphological and physiological parameters. The behavioral phenotypes of XYY males, like chromosomally normal ones, are the result of both genotypic and environmental processes. To ascribe to a single chromosome specific behavioral effects fails to take account of a broad range of pertinent environmental factors and ignores the fact that the phenotype is the result of the total integrative properties of the genome interacting with the environment.

ing paternal

COURT BROWN,~*

REFERENCES

15. 16. 17. 18. 19.

MONTAGU,A. Chromosomes and crime. Psychology Today 2,43, 1968. SHELDON,W. H. Varieties of Delinquent Youth. Harper, New York, 1949. GLUECK,S. and GLUECK,E. Physique and Delinquency. Harper, New York, 1956. LINDZEY, G. Behavior and morphological variation. In: Genetic Diversity and Human Behavior. SPUHLER, J. N. (Ed.), p. 227. Aldine Publishing Co., Chicago, 1967. GALTON, SIR F. Inquiries into Human Faculty and Its Development. Macmillan, New York, 1883. DUGDALE,R. L. The Jukes: A Study in Crime, Pauperism, Disease and Heredity. Putnam’s, New York, 1910. GODDARD,H. H. The Kallikak Family; A Study in the Heredity of Feeblemindedness. Macmillan, New York, 1912. STERN,C. Principles of Human Genetics. Freeman, San Francisco, 1960. CHICAGO CONFERENCE. Standardization in Human Cytoaenetics. Birth Defects. Original Article Series II, 2, The National Foundation, New York, 1966.STOCK,R. W. The XYY and the Criminal. The New York Times Magazine, October 20, p. 30, 1968. PRITCHARD, M. Klinefelter’s syndrome and behaviour. Lancet 2, 762, 1964. VALENTINE, G. H. and SERGCVCH,F. A new dilemma. Lancet 2, 151, 1967. ZUBLIN, W. A new dilemma. Lancet 2, 615, 1967. GOODMAN,R. M., SMITH,W. S. and MIGEON, C. J. Sex chromosome abnormalities. Nature, Lond. 216, 942, 1967. LEFF,J. P. and SCOTT,P. D. XYY and intelligence.Lancet 1, 645, 1968. COURTBROWN, W. M., PRICE, W. H. and JACOBS,P. A. The XYY male. Br. med. J. 4, 513, 1968. SUINN, R. M. YY syndrome and sampling techniques. Lancer 1, 157, 1969. COURTBROWN,W. M. Males with an XYY sex chromosome complement. J. med. Genet. 5,341,1968. MACLEAN,N. Sex chromatin surveys of newborn babies. In: The Sex Chromatin. MOORE,K. L. (Ed.),

20.

SERGOVICH, F. R. Chromosome studies in unselected neonates. Abstr. Am. Sot. Hum. Genet., Austin,

21.

SANDBERG, A. A., KOEPF,G. F., ISHIHARA, T. and HAUSCHKA,T. S. An XYY human male. Lancet 2, 488, 1961. HAUSCHKA,T. S., HASSON,J. E., GOLDSTEIN,M. N., KOEPF,G. F. and SANDBERG, A. A. An XYY man with progeny indicating familial tendency to non-disjunction. Am. J. Hum. Genet. 14, 22, 1962. BALODIMOS, M. C., LISCO,H., IRWIN, I., MERRILL,W. and DINGMAN,J. F. XYY karyotype in a case of familial hypogonadism. J. clin. Endocr. Metab. 26, 443, 1966. CASEY,M. D., SEGALL,L. J., STREET,D. R. K. and BLANK, C. E. Sex chromosome abnormalities in two state hospitals for patients requiring special security. Nature, Lond. 209, 641, 1966. JACOBS,P. A., BRUNTON,M., MELVILLE,M. M., BRITTAINR. P. and MCCLEMONT,W. F. Aggressive behaviour, mental sub-normality and the XYY male. Nature, Lond. 208, 1351, 1965.

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

Saunders, Philadelphia, Texas, p. 33, October, 22. 23. 24. 25.

1966. 1968.

168 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58.

59. 60.

SEYMOURKESSLERAND RUDOLF H. Moos PRICE, W. H., Strong, J. A., WHATMORE,P. B. and MCCLEMONT,W. F. Criminal patients with XYY sex-chromosome complement. Lancet 1, 565, 1966. CASEY, M. D., BLANK, C. E., STREET,D. R. K., SEGALL,L. J., MCDOUGALL, J. H., MCGRATH, P. J. and SKINNER,J. L. YY chromosomes and anti-social behaviour. Lancet 2, 859. 1966. GRIFFITHS,A. W. and ZAREMBA,J. Crime and sex chromosome anomalies..Bv. med. J. 4, 622, 1967. WEINER, S., SUTHERLAND,G., BARTHOLOMEW,A. A. and HUDSON. B. XYY males in a Melbourne prison. Lancet 1, 150, 1968. TELFER,M. A., BAKER, D., CLARK, G. R. and RICHARDSON, C. E. Incidence of gross chromosomal errors among tall criminal American males. Science 159, 1249, 1968. COURT BROWN, W. M., PRICE, W. H. and JACOBS, P. A. Further information on the identity of 47,XYY males. Br. med. J. 2, 325, 1968. HUNTER, H. Chromatin-positive and XYY boys in approved schools. Lancet 1, 816, 1968. CLOSE.H. G., GOONETILLEKE, A. S. R., JACOBS,P. A. and PRICE, W. H. The incidence of sex chromosomal abnormalities in mentally subnormal males. Cytogenetics 7, 277, 1968. BARTLETT,D. J., HURLEY, W. P., BRAND, C. R. and POOLE,E. W. Chromosomes of male patients in a security prison. Nature, Lond. 219, 351, 1968. NIELSEN,J., TSUBOI, T., STIRRUP,G. and ROMANO, D. XYY chromosomal constitution in criminal psychopaths. Lancet 2, 576, 1968. .&KESSON,H. O., FORSSMAN,H. and WALLIN, L. Chromosomes of tall men in mental hospitals. Lancer 2, 1040, 1968. DALY, R. F. Neurological abnormalities in XYY males. Nature, Lond. 221, 472, 1969. MINTZER, R., PERGAMENT,E., BERLOW, S. and SATO, H. The XYY syndrome. J. Pediat. 72, 572 (abstr.), 1968. PERGAMENT,E., SATO, H., BERLOW, S. and MINTZER, R. YY syndrome in an American Negro. Lancet 2, 281, 1968. GOODMAN,R. M., MILLER, F. and NORTH, C. Chromosomes of tall men. Lancet 1, 1318, 1968. MATTHEWS,M. B. and BROOKS,P. W. Aggression and the YY syndrome. Lancet 2,355, 1968. BORGAONKAR,D. S., MURDOCH, J. L., MCKUSICK, V. A., BORKOWF,S. P., MONEY, J. W. and ROBINSON, B. W. The YY syndrome. Lancet 2,461, 1968. THORBURN,M. J., CHUTKAN, W., RICHARDS,R. and BELL, R. XYY sex chromosomes in a Jamaican with orthopaedic abnormalities. J. med. Genet. 5, 215, 1968. LISKER,R., ZENZES, M. T. and FONESCA,M. T. YY syndrome in a Mexican. Lancer 2, 635, 1968. FORSSMAN,H., AKESSON,H. 0. and WALLIN, L. The YY syndrome. Lancet 2,779, 1968. NIELSEN,J. Y chromosomes in male psychiatric patients above 180 cm. tall. Br. J. Psychiat. 114, 1589, 1968. WIENER,S. and SUTHERLAND,G. A normal XYY man. Lancet 2, 1352, 1968. HASHI, N., TSUTSUMI,S. and TSUDA, K. The first case report on the YY syndrome (XYY male) in Japan. Proc. Jap. Acad. 45,63, 1969. JACOBS,P. A. PRICE, W. H., COURT BROWN, W. M., BRITTAIN,R. P. and WHATMORE,P. B. Chromosome studies on men in a maximum security hospital. Ann. Hum. Gene?., Lund. 31, 339, 1968. COURT BROWN, W. M. Genetics and crime. J. Roy. CON. Phys. 1, 311, 1967. COURT BROWN, W. M., HARNDEN, D. G., JACOBS,P. A., MACLEAN, N. and MANTLE, D. J. Privy Count. Med. Rex Council, Special Report Series No. 305. H.M.S.O., London, 1964. MONTERO,E. and DURAN, I. Polisomia gonosomica XYY. An. Desarrollo 13, 215, 1965. NIELSEN,J., CHRISTENSEN, A., JOHNSEN,S. G. and FRBLAND, A. Psychopathology and testis histology in a patient with the XYY syndrome. Acta med. stand. 180, 747. 1966. WILTON, E. and LEVER,A. The YY syndrome. Lance? 1, 1156, 1966. THOMPSON,H., MELNYK, J. and HECHT, F. Reproduction and meiosis in XYY. Lancet 2, 831, 1967. HUNTER, H. YY chromosomes and Klinefelter’s syndrome. Lancer 1, 984, 1966. KELLY, S., ALMY, R. and BARNARD, M. Another XYY phenotype. Nature, Lond. 215,405, 1967. JACOBS,P. A., HARNDEN, D. G., BUCKTON, K. E., COURT BROWN, W. M., KING, M. J., MCBRIDE, J. A., MACGREGOR, T. N. and MACLEAN,N. Cytogenetic studies in primary amenorrhoea. Lancer 1, 1183, 1961. GROUCHY, J. DE, BLONDET, P., ROYER, P., VERMEIL,G. and LAMY, M. Syndrome de Turner et caryotype A 47 chromosomes. Ann. G&z&. 6,25, 1963. VIGNETTI,P., CAPOTORI,L. and FERRANTE,E. XYY chromosomal constitution with genital abnormality. Lancer 2, 588, 1964.

THE XYY 61. 62. 63. 64. 65. 66. 67. 68. 69. 70.

71. 72. 73. 74. 75. 76. 77.

78. 79. 80. 81. 82. 83. 84. 85. 86. 87.

88.

89.

90. 91.

KARYOTYPEAND CRIMINALITY:A REVIEW

169

FRANKS, R. C., BUNTING,K. W. and ENGEL, E. Male pseudohermaphrodism with XYY sex chromosomes. J. clin. endocr. Metab. 27, 1623, 1967. CARAKUSHANSKY,G., NEU, R. L. and GARDNER, L. I. XYY with abnormal genitalia. Lancet 2, 1144, 1968. FORSBERG,J. G., HALL, B. and RYDEN, A. B. V. A case of testicular feminisation with chromosome mosaicism. Acta obstet. gynec. stand. 44,491, 1965. RICHARDS, B. W. and STEWART, A. The YY syndrome. Lancet 1,984, 1966, FORSSMAN,H. and HAMBART, G. Chromosomes and antisocial behaviour. Lancet 2,282, 1966. FORSSMAN,H. Epilepsy in an XYY man. Lancet 1, 1389, 1967. WELCH, J. P., BORGAONKAR,D. S. and HERR, H. M. Psychopathy, mental deficiency, aggressiveness and the XYY syndrome. Nature, Lond. 214, 500, 1967. COWIE, J. and KAHN, J. XYY constitution in prepubertal child. Br. med. J. 1, 748, 1968. BEEMAN,E. A. The effect of male hormone on agressive behavior in mice. Phvsiol. 2002.20.373. 1947. ISMAIL,k. A. A., HARKNESS,R. A., KIRKHAM, <. E., LORAINE,J. A., WHATMORE,P. B. and BRI~TAIN, R. P. Effect of abnormal sex-chromosome complements on urinary testosterone levels. Lancet 1, 220, 1968. RUDD, B. T., GALAL, 0. M. and CASEY, M. D. Testosterone excretion rates in normal males and males with an XYY complement. J. med. Genet. 5, 286, 1968. PAPANICOLAOU,A. D., KIRKHAM, K. E. and LORAINE,J. A. Abnormalities in urinary gonadotrophin excretion in men with a 47,XYY sex chromosome constitution. Lancet 2,608, 1968. PRICE, W. H. The electrocardiogram in males with extra Y chromosomes. Lancer 1, 1106, 1968. HOPE, K., PHILIP, A. E. and LOUGHRAN,J. M. Psychological characteristics associated with XYY sex-chromosome complement in a state mental hospital. Br. J. Psychiat. 113, 495, 1967. PRICE, W. H. and WHATMORE,P. B. Behaviour disorders and pattern of crime among XYY males identified at a maximum security hospital. Bv. med. J. 1, 533, 1967. BANDURA, A. and WALTERS, R. Adolescent Aggression. Ronald Press, New York, 1959. BECKER,W. Consequences of different kinds of parental discipline. In: Review of Child Development Research, Vol. 1, p. 169. HOFFMAN, M. and HOFFMAN, L. (Ed.), Russell Sage Foundation, New York, 1964. SEARS, R., MACCOBY, E. and LEVIN, H. Patterns of Child Rearing. Row & Peterson, Evanston, Ill., 1957. SCHACHTER,S. and SINGER, J. Cognitive, social and physiological determinants of emotional state. Psychol. Rev. 69, 379, 1962. ALDRICH, C. K. Expectations of crime. World Med. J. 14,40, 1967. ROSENTHAL,A. Experimenter Effects in Behavioral Research. Appleton-Century-Crofts, New York, 1966. CAPRA, P. and DITTES, J. Birth order as a selective factor among volunteer subjects. J. Abnorm. Sot. Psychol. 64, 302, 1962. LEIPOLD,W. D. and JAMES,R. L. Characteristics of shows and no-shows in a psychological experiment. Psychol. Rept. 11, 171, 1962. BELL, C. R. Personality characteristics of volunteers for psychological studies. Br. J. sot. clin. Psychol. 1, 81, 1962. ROBINSON,A. and PUCK, T. T. Studies on chromosomal nondisjunction in man. II. Am. J. hum. Genet. 19, 112, 1967. BERKOWITZ, L. Aggression: A Social and Psychological Analysis. McGraw-Hill, New York, 1962. SHORT, J. F. Juvenile delinquency: The sociocultural context. In: Review of Child Development Research, Vol. II, p. 423. HOFFMAN, M. and HOFFMAN,L. (Ed.), Russell Sage Foundation, New York, 1966. KOPELL, B. S., WITTNER, W. K. and WARRICK, G. The effects of stimulus differences, light intensity and selective attention on the amplitude of the visual averaged evoked potential in man. Electroenceph. clin. Neurophysiol. 26, 619, 1969. ENDLER,N. S. and HUNT, J. McV. S-R inventories of hostility and comparisons of the proportions of variance from persons, responses and situations for hostility and anxiousness. J. Personal. Sot. Psychol. 9, 309, 1968. RAUSH, H., DITTMAN, A. and TAYLOR, T. Person, setting and change in social interaction. Human Relations 12, 361, 1959. MOYER, K. E. Kinds of aggression and their physiological basis. Commun. behav. Biol., Part A, 2, 65, 1968.

170 92. 93. 94. 95. 96. 97. 98. 99. 100. 101. 102.

SEYMOURKESSLERAND RUDOLFH. Moos SCHUTZ, W. C. FIRO: A Zbree Dimensional Theory of Interpersonal Behavior. Holt, Rinehart, & Winston, New York, 1958. HEIDER,F. The Psychology of Interpersonal Relations. John Wiley, New York, 1958. VANDENBERG, S. G. The sex chromosomes and behavior: A critical review. (Unpublished). HIENZ, H. A. YY-syndrome forms. Lancet 1, 155, 1969. COOPER,H. L., KUPPERMAN,H. S., RENWN, 0. R. and HIRSCHHORN,K. Sex-chromosome mosaicism of type XYY/XO. New Eng. J. Med. 266,699, 1962. UCHIDA, I. A., RAY, M. and DUNCAN, B. P. 21 trisomy with an XYY sex chromosome complement. J. Pediat. 69, 295, 1966. DOBZHANSKY,TH. A review of some fundamental concepts and problems of population genetics. Cold Spring Harbor Symp. Quant. Biol. 20, 1, 1955. COURTBROWN,W. M. Sex chromosomes and the law. Lancet 2,508, 1962. NIELSEN,J. Klinefelter’s syndrome and behaviour. Lancer 2, 587. 1964. CASEY, M. D., STREET, D. R. K., SEGALL, L. J. and BLANK, C. E. Patients with sex chromatin abnormality in two state hospitals. Ann. hum. Genet. 32, 53, 1968. MACLEAN,N., COURTBROWN,W. M., JACOBS,P. A., MANTLE,D. J. and STRONG, J. A. A survey of sex chromatin abnormalities in mental hospitals. J. Med. Genet. 5, 165, 1968.

NOTE ADDED IN PROOF: Another behaviorally normal XYY male detected because of a poor reproductive history has been reported. *OSHe is 183 cm tall, bringing the number of adult XYY cases detected for reasons other than height to 23. 11 of which are greater than or eoual to 72 in. in height. In addition, reports of a prepubertal child with neurological deficits, no behavioral difficulties and a normal IQ,loP of a pair of XYY monozygotic twinslo and of negative findings in a survey of 67 tall prison inmateslaG have appeared. MAVALWALAet aLlo discuss the varying dermatoglyphics found associated with some XYY provides a comprehensive bibliography on the XYY literature. individuals and BORGAONKAR’~”

ADDITIONAL

REFERENCES

M. A. and MACR*ITYRE, M. N. A normal XYY man. Lancet 1, 680, 1969. 103. STENCHEVER, 104. DALY, R. F., CHUN, R. W. M., EWANOWSKI,S. and OSBORNE,R. H. The XYY condition in childhood: Clinical observations. Pediatrics 43, 852, 1969. 105. RAINER, J. D., JARVIK, L. F., ABDULLAH,S. and KATO, T. XYY karyotype in monozygotic twins. Lancet 2, 60, 1969.

107.

KNOX, S. J. and NEVM, N. C. XYY chromosomal constitution in prison populations. Nature 222, 596, 1969. MAVALWALA,J., PARKER, C. E. and MELNYK, J. Dermatoglyphics of the XYY syndrome. Am. J.

108.

BORGAONKAR, D. S. 47,XYY bibliography.

106.

Phys. Anthrop.

30, 209, 1969. Ann. G&et.

12, 67, 1969.