Jay Joseph Psy.D. The Gene Illusion Chapters

CHAPTER ONE

| Introduction.

It has been observed that “the knowledge that certain diseases run in families is thousands of years old.”

[1]

Today, it is

widely

understood

that a trait or condition “running in the family” can be explained by any number of

environmental factors

related to the

physical, social, and

psychological environments shared by family members.

For this reason, most genetic

researchers recognize

that family studies are unable to

disentangle the potential

influences of genes and environment. For

example, a pair of prominent

genetic researchers in psychiatry

acknowledged that family studies can provide only “the initial

hint that a disorder might have a

genetic

component,”

because “disorders can ‘run

in families’ for nongenetic reasons such as

shared environmental

adversity, viral

transmission, and social learning.”

[

Family studies identify persons manifesting a given trait or condition, and attempt to determine whether their

biological

relatives

are similarly

affected more often than are members of the general population or a control

group.

If a condition is found

to aggregate

in families, it is said to be

familial. However, “familial” is not the same as

“genetic.” Unfortunately, many people

view these terms as

being synonymous, when in fact they

are not.

Moreover, some researchers, and more frequently

reports in

the

popular media, continue to

erroneously cite family

data in

support of genetics.

CHAPTER TWO

Twin

esearch: Misunderstanding Twins, From Galton to the 21st

Century.

Joseph looks into the history of twin research in Chapter 2, and documents the largely unknown story of its

origins in eugenics

and the German “racial hygiene” movement.

[3]

He quotes many documents from the first half

of the 20th century, many of which are

translated from the original German for the first time. England’s Francis

Galton founded the eugenics movement in the 19th century,

and became the first person to propose using twins to

study heredity. He is usually regarded as the father of twin research. It is worth

noting that Galton, who believed

that, biologically speaking,

there was only one type of twi

n pair

oncluded in favor of heredity

the basis of

what

today

would consider sketchy, responder-biased, and second-hand reports. Galton saw the histories of

twins

evidence of human

genetic predestination, or as he put it, “the clocks of their two lives move regularly at

the

same rate, governed by

their internal

mechanism.”

[4]

Galton did not personally study twins, and relied on

reports

in which twins were said to have become

sick and

recovered at the same time, which he saw as evidence

of an

“intimate . . . constitutional resemblance.”

[5]

Galton believed

that

heredity maps out a behavioral life plan for

each

person in the same way that it might influence, for example, baldness

or skin pigmentation

. He argued that

psychological traits are under as much hereditary control as physical traits,

failing to

recognize that the behavioral

resemblance

of twin pairs could be the result of their similar environment, similar

treatment,

and

close emotional

bond. Thus, Galton became the first in a long line of twin researchers to attribute

twins’ behavioral resemblance

mainly

to hereditary factors.

The 1920s saw the development of the “classical twin method,”

more commonly known as “the twin

method.” The twin method

compares the resemblance of reared-together identical twin pairs (also known as

monozygotic, or MZ), who share 100% genetic

similarity, versus the resemblance of reared-together same-sex

fraternal twin pairs (also known as dizygotic, or DZ), who average a

50% genetic similarity. (Twin resemblance is

usually measured with concordance rates or correlations.) Based on the assumption

that the childhood and adult

environments of both types of twins are comparable, known as the

equal environment assumption

(or

“EEA"), twin

researchers attribute to genetic factors the usual finding of a significantly greater resemblance among identical

versus

same-sex fraternal twin pairs. In 1937, American researchers Horatio Newman and colleagues published

the first systematic study of

“reared-apart” twins.

[6]

Leading German racial hygienists such as Ernst Rüdin and Hans Luxenburger (the latter published the first

schizophrenia twin

study in 1928) pushed hard for compulsory eugenic sterilization laws well before 1933. In the

United States, many states had already

passed eugenic sterilization laws, and most twin research was carried out

by eugenicists eager to supply data in support of the

cause. For the most part, however, contemporary accounts

the history of twin research have failed to highlight the fact that twin

research has its origins in

the

eugenics

movement.

Beginning with Galton, Joseph discusses the various ways that twins have been used for research

purposes,

as well as some of

the methodological problems discussed by critics. Due mainly to its association with

eugenics,

interest in twin research waned in the

late 1940s and 1950s, but began a revival in the late 1960s that

continues to

the present time. Today, twin studies constitute the

main pillar of support for genetic theories in

psychiatry and

psychology, in part because the underlying assumptions of twin research

are rarely questioned in

the authoritative

texts of these disciplines. However, past and present critics have made a strong argument

that,

due to

researchers’ reliance on unsupported theoretical assumptions and other factors, the twin method provides

scientifically acceptable evidence in support of genetic influences

psychological trait variation (such as IQ

and

personality) and

psychiatric disorders.

In 1960, psychiatrist and family therapy pioneer Don Jackson wrote a powerful critique of schizophrenia

genetic research.

[7]

that time there were five published schizophrenia studies using the twin method, with

Franz Kallmann’s 1946 study being the largest

and most influential. (Schizophrenia adoption studies did not

appear until the mid-1960s.) Jackson made 11 major points in his

critique, and although all did not originate with

him, together they made a strong case that twin research contains serious and

invalidating flaws. Jackson’s

main

points were as follows:

(1) In discussing family (consanguinity) studies, Jackson noted that conditions can run in families for

environmental reasons.

(2) There were no genetic studies of schizophrenia in which researchers made diagnoses blindly. The results

of these studies

were therefore susceptible to the researchers’ bias.

(3) There were important biases in twin study diagnostic proc

edures

, and the question of whether

schizophrenia is a reliable

diagnosis remained open. An additional bias was introduced by the methods used

to obtain twin samples, which could lead to

inflated concordance rates.

(4) Contrary to genetic expectations, fraternal twin pairs were more concordant

for schizophrenia

than non-

twin sibling pairs,

even though both

sets have the same genetic relationship to each other.

(5) Contrary to genetic expectations, female identical pairs were more concordant than male identical pairs.

(6) Contrary to genetic expectations, female fraternal pairs were more concordant than male fraternal pairs.

(7) Contrary to genetic expectations, same-sex fraternal pairs were more concordant than opposite-sex

fraternal pairs.

(8) Individual case histories of reared-apart identical twins concordant for schizophrenia provide no important

evidence for

genetic factors because they were few in number (two), and because the pairs grew up in

similar

environments and had an

interactive relationship with each other.

(9) Identical twin pairs grow up in a more similar environment, and are treated more similarly, than fraternal

pairs. Therefore,

the greater resemblance of identical pairs for schizophrenia could be explained by the more

similar environment they

experience.

(10) The unique psychological bond or “ego fusion” of identical twins contributes to their higher concordance

rate for

schizophrenia on the basis of association and identification. Furthermore, the nature of the identical

twinship itself might create

conditions leading to the identity problems often experienced by people diagnosed

with schizophrenia.

(11) There is a striking similarity between reports of

folie à deux

(shared psychotic disorder) and the case

histories of identical

twin pairs judged concordant for schizophrenia.

Jackson suggested that schizophrenia twin research (and by implication, twin research in other areas of

psychiatry) may have

recorded little more than the greater environmental similarity and “ego fusion” experienced

by identical versus fraternal twin pairs.

Although some twin researchers subsequently adjusted their methods on

the basis of Jackson’s criticism,

most disagreed with

Jackson’s

position that the twin method was a fundamentally

flawed instrument due to its inability to disentangle genetic and

environmental

influences on behavioral disorders.

Today, Jackson’s critique is a forgotten document in the sense that the twin

method is more

popular than ever,

even though none

of Jackson’s 11 major points has ever been refuted.

As seen above (Point #10), Jackson argued that the unique psychological bond

of identical pairs not only

contributes to their

elevated schizophrenia concordance rates when compared with fraternal pairs, but may

even

be an additional cause of

chizophrenia.

According to Jackson:

“The identity problems of the schizophrenic, most often stressed by psychodynamically oriented writers,

could

find no better

nidus than in the intertwining of twin identities, in the ego fusion that in one sense

doubles the

ego (because the other is felt as

part of the self) and in another sense halves it (because the self

is felt as

part of the other).”

“If the psychodynamic thesis is correct, if ego fusion in a particular family environment can be expected to

lead to joint

madness, then a plausible hypothesis—contrary to the genetical hypothesis—would be that,

according to the degree of

likeness in siblings, we will find an increased concordance for schizophrenia,

without concern for genetic similarity.”

“Psychosis by association apparently requires the nidus of social isolation for its hatching . . . These

characteristics increase

the separation of the twin-pair from the rest of the world and foster a joint ego fusion.

. . . The attempt of one to be like the other

is not dissimilar to the ego fusion of some twins.”

Here, Jackson discusses how the intimate bond and “ego fusion” experienced by identical twin pairs might

weaken or blur the

psychological boundaries between them, leading to higher concordance for behavioral

disorders such as schizophrenia. As an

alternative “plausible hypothesis” to genetic interpretations of comparisons

between identical and fraternal twin pairs, Jackson

theorized, “According to the degree of likeness in siblings, we

will find an increased concordance for schizophrenia, without concern

for genetic similarity.” Slightly modifying

Jackson’s position we might say that, according to the degree of

environmental similarity

experienced by siblings,

we would expect greater behavioral similarity, without concern for their genetic relationship.

Twin researchers of the 1960s and 1970s frequently addressed Jackson’s “ego fusion” theory in an attempt

to refute

entire

critical analysis of the twin method. They

often

argued that, according to Jackson’s theory,

individual

identical twins as a population

would

be expected to

have a higher rate of schizophrenia than would

members of

the single-born population. Kringlen’s 1967 position was

typical:

“The findings furthermore cast doubt on Jackson’s (1960) ‘confusion of ego identity theory’ of schizophrenia.

. . According to

Jackson, the monozygotic twinship involves problems of ‘isolation, association and

identification.’ This hypothesis stimulated

Rosenthal . . . to investigate if schizophrenia in fact was more

frequent in twins [compared with singletons]. . . . Rosenthal

analyzed the twin investigations published by

Luxenburger . . . and Essen-Möller and could not support this theory of Jackson.”

[8]

However, Jackson’s theory did not require individual identical twins to develop schizophrenia at higher rates

than single-born

individuals. Jackson argued that the confusion of ego identity, experienced most strongly by

identical twins, could explain why the co-

twin of a person diagnosed with schizophrenia is more likely to receive

this diagnosis than another family member with whom the

twin does not share comparable levels of ego fusion. His

theory centered on why the

second

twin is diagnosed with schizophrenia,

not the first.

Jackson’s most

telling observation

, which remains highly relevant today, was that

n a sample of

pairs with

the

same

genetic

relationship to

each other, those pairs experiencing a more similar environment and a closer

emotional

bond were consistently more

concordant for

schizophrenia. In essence, Jackson argued that the

theoretical basis

of the twin method—the identical-fraternal “equal

environment

assumption”—is false (see the

discussion of

Chapter 3 below).

In Chapter 2, Joseph provides a timely overview of the history of twin research in the context of the social,

political, and scientific

environments in which it was performed. More importantly, he lays the groundwork for

argument, which he elaborates upon in

subsequent chapters of

The Gene Illusion

, that twin research is of

doubtful

scientific validity when it is used to identify genetic

influences on human behavior. Thus, Joseph

concludes the

chapter by writing that, beginning with Galton, five generations of twin

researchers have failed to

understand (1)

that environmental factors are the most plausible explanation for the greater behavioral

resemblance of identical

versus fraternal twin pairs, and (2) that methodological flaws, bias, and the failure to

recognize

environmental

confounds call into question claims that studies of reared-apart twins supply evidence in

favor of genetic influences

psychological trait variation (see the discussion of Chapter 4 below).

CHAPTER THREE

The Twin Method: An Environmentally Confounded Research

Method.

Following Jackson and others,

in this chapter

Joseph looks closely at the theoretical underpinnings of

he twin

method

Although

the twin method is

the

main tool of the fields of

behavior genetics

[9]

and

psychiatric

genetics

[10]

there

s overwhelming evidence

that

identical twin

pairs

experience much more

similar

environments than

fraternal

pairs

. P

erhaps more important,

we have seen that

identical

pairs

experience a stronger psychological

bond and more

often

experience identity confusion.

[11]

Twin researchers

sually

concede

he point that identical

twin pairs experience more similar environments

, yet

continue to uphold the validity of the twin

method

and the

equal environment assumption

(EEA)

the

basis of two

claims. The first is that, although identical and fraternal

twin

pair

environments

are different,

critics

must identify the

“trait-

relevant”

environmental factors for which

identical and fraternal

twins

experience dissimilar

environments.

(By “trait relevant,” twin

researchers mean

aspects of the environment that have

been shown to

contribute to the

trait in

question. For example, exposure to

trauma contributes to post-

traumatic stress

disorder.) However,

because

a basic tenet of

science holds that the

burden of proof falls

on the

proponents of a theory

and

not on

its

critics,

[12]

twin

researchers themselves bear

the

burden of proof

for showing that identical and fraternal twins

are not

differentially exposed to

potentially

relevant environmental

factors. Moreover,

although faced with a similar

problem, twin

researchers do not make

the

“trait

relevant” argument

when

discussing potential

environmental

confounds in

family studies

. In this

case

they

are willing to

concede that,

because family

members

share a

common

environment (“trait-relevant” or not),

one

cannot

draw valid

conclusions in favor of genetic

influences on

the basis

of a

family resemblance of a trait.

The second defense of the twin method used by contemporary twin researchers is the claim that identical

twins “create”

similar

environments for themselves by virtue of their greater genetically-caused similarity of

behavior.

[13]

Therefore the twin

method’s validity,

according to some twin researchers, is based on determining

why—not whether—identical twins experience

similar environments than

fraternals. Twin researchers and

popularizers of their work, however, fail to understand that

the

reason

identical

airs

experience more similar

environments than fraternal

pairs

, be it environmental or genetic, is

irrelevant in assessing

the validity of the EEA.

For example, suppose that

schizophrenia is caused solely by exposure to a toxic

chemical. Because identical

twin

pairs

spend much more time together than fraternal

pairs

, it is

much more likely that both members of

an identical

twin

pair will

exposed to the chemical, and be subsequently diagnosed with schizophrenia,

than it is that both

members of a fraternal pair will

exposed and diagnosed. However, even if identicals do indeed “create” more

similar

environments for themselves than do

fraternals

on the basis of their greater genetic similarity, it would be

erroneous to

conclude that higher

identical versus fraternal

concordance

for schizophrenia is evidence that the

condition has a genetic

component. In this example—regardless of

why

identical

pairs

are

together more often—

higher identical twin

pair

concordance is

caused solely by identicals’ propensity to be together more

often than

fraternal

pairs

, which leads them to be more similarly

exposed to the toxic chemical that causes schizophrenia.

Thus, the only relevant question in

ssessing

the validity of the twin method is

whether

—not why—identical

twin

pairs

experience more

similar environments than fraternal

pairs

. Moreover, the “twins create their

environment”

argument uses circular

reasoning, because the

evidence that twins’ behavioral similarity is caused

by genetics is

implicitly derived from the results of

previous twin studies. Therefore, Joseph

nd other critics

argue

both family

and

twin studies

are unable to disentangle

the

potential

role

genetic

and environmental

influences

psychological trait

variation or

psychiatric disorders.

oseph

concludes that there is

reason to

that

the twin

method measures anything

other than the more

similar treatment, greater environmental

similarity,

and

closer

psychological association

experienced by identical versus fraternal twin pairs.

CHAPTER FOUR

Genetic Studies of Twins Reared Apart: A Critical Review.

Joseph begins Chapter 4 with an examination of stories released by twin researchers, and often reported by

journalists,

about

supposedly

separated

(reared-apart) twins who, upon being reunited, are said to share an

amazing set of

common features, traits,

preferences,

etc. He points out,

however, that most pairs come to the

attention of

researchers and journalists

because of

their

similarities. It’s

similar to the old “dog bites person

versus

person

bites dog” rule in journalism. A dog biting a person isn’t

newsworthy because it’s a

common occurrence,

whereas

a person biting

a dog is news because it is an

usual occurrence.

If we read several articles

describing

a person

biting a dog, we would be wrong to conclude

that people bite dogs more

frequently than dogs bite

people. The

same is true for twins. Stories of similar reared-apart twin

pairs

are news because

they are

interesting

and

compelling;

stories about

dissimila

airs

are not.

More importantly, there are many

environmental

(non-genetic) factors shared by reared-apart identical twins

(and by reared-

together identical twins) that would lead them to resemble each more than two randomly selected

members of the world’s population.

These factors include

They are exactly the same age
They are the same sex
They are almost always the same ethnicity
Their appearance is strikingly similar (which will elicit more similar treatment)
They usually are raised in the same socioeconomic class
They usually are raised in the same culture
They shared the same prenatal environment
They typically spent a certain amount of time together in the same family environment, were aware of each
other’s existence when studied, and often had regular contact over a long period of time

All of these factors work towards increasing the behavioral

resemblance of

reared-apart identical twins for

non-genetic reasons, yet are rarely discussed in popular accounts

of individual pairs.

hat

itically

important to

understand

that the behavioral resemblance of reared-apart

identical twins is a product of the

cohort effect

which

accounts for similarities in people’s behaviors and

preferences that arise from the characteristics of the

historical periods and

cultural milieu in which they experience

stages of life at the same time.

A typical example of the failure to recognize cultural and cohort influences on twin resemblance, and to

erroneously

attribute this

resemblance to genetics, is found in journalist Kay Cassill’s 1982 description of reared-

apart identical twins Keith

Heitzman and

Jack Hellback,

who grew up in Louisiana:

“Although the mighty Mississippi divided these two physically, it could not separate their parallel lives. The

welder from

one

side and the

pump mechanic from the other found that they are both allergic to ragweed

and

dust. Both had done

poorly in

school. Both disliked sports

and had cut their gym classes whenever

they

could. They are both addicted to

candy. Their

similarity of dress includes a penchant for

wearing

cowboy

hats, which matches their parallel interest in

guns and hunting.”

[14]

As a critic commented, “Even if ‘the mighty Mississippi divided’ the twins, the fact that they both wear cowboy hats

and like

hunting is

not that

unusual for two [white] working-class men in the same region of Louisiana.”

[15]

The

same point can be made

about the

celebrated

reared-apart

“Jim Twins,” two working-class white men who grew

up in the same

region of Ohio at the same time.

Joseph concludes that the stories of individual pairs of reared-apart identical twins, while interesting

rom

journalistic perspective

, tell us