Somatotype and Constitutional Psychology

Somatotype and constitutional psychology is a theory developed by William Sheldon that links body shape to personality traits. He proposed three main body types: ectomorphs, who are slim and introverted; mesomorphs, who are muscular and assertive; and endomorphs, who are rounder and sociable. While historically influential, the theory is now considered outdated and overly deterministic, but it helped spark early interest in how biology might shape behavior.

Key Takeaways

Theory: Somatotype and constitutional psychology is William Sheldon’s idea that body shape reflects personality traits, dividing people into ectomorphs, mesomorphs, and endomorphs.
Classification: Ectomorphs are slim and introverted, mesomorphs are muscular and assertive, and endomorphs are rounder and more sociable—each linked to distinct temperamental patterns.
Evidence: Sheldon claimed biological foundations for personality, but his data and methods lacked scientific rigor, relying heavily on subjective observation and small samples.
Criticism: Modern psychology rejects the theory as overly deterministic and body-based, warning that it reinforces stereotypes and ignores environmental or cultural factors.
Legacy: Despite being outdated, Sheldon’s work influenced early personality and criminology research and paved the way for later studies on the biological roots of behavior.

What is constitutional psychology?

Constitutional psychology is an approach that tries to explain personality and behaviour in terms of a person’s biological or physical makeup.

In other words, it’s the study of how the body’s structure and inherited traits might shape how someone thinks, feels, and acts.

Key ideas include:

Heredity matters: People’s natural (genetic or constitutional) differences were thought to make some individuals stronger, more capable, or more “fit” than others.
Organic focus: Instead of looking at thoughts or emotions directly, researchers like Cesare Lombroso looked for clues in the body — measuring skulls, faces, and other features.
Personality and biology: Later researchers, including Sheldon, continued this idea by trying to match body types with personality traits.
Clinical observation: The approach influenced psychiatry and psychology, leading to attempts to classify people based on physical and mental characteristics.

While modern psychology now rejects these biological determinist ideas, they were an important early attempt to connect biology and behaviour.

W. H. Sheldon’s Three Somatotypes

William Sheldon’s Theory explored whether a person’s body type (or physical build) could be linked to their personality and behaviour, especially criminal or delinquent behaviour.

This idea formed part of an older scientific approach known as the constitutional school in psychology, to explain behaviour through biological or physical factors rather than social ones.

The Core of Sheldon’s Theory

Sheldon believed that people could be grouped into three main body types, which he called somatotypes.

He argued that each body type was connected to certain temperamental traits and even to tendencies toward deviant or criminal behaviour:

Ectomorphs: slim and fragile; thought to be quiet, anxious, and restrained.
Mesomorphs: muscular and athletic; thought to be energetic, assertive, and more likely to take risks or get into trouble.
Endomorphs: soft and round; thought to be sociable, relaxed, and comfort-seeking.

Sheldon even created a three-digit rating system to describe how much of each body type a person had, with each scored from 1 to 7.

Scores were based on body measurements (height, weight, skinfold thickness, and body circumferences) combined with visual judgment.

For example, someone rated 4–6–3 would have moderate endomorphy, high mesomorphy, and low ectomorphy.

Human body types. Three figures. Forms: ectomorph, mesomorph and endomorph.

1. Ectomorph (Cerebrotonic Temperament)

Ectomorphs represent the slimmest and most delicate body type and were thought to be strongly influenced by the brain and nervous system.

Physical Characteristics

Ectomorphs are characterised by a slender and fragile build.

Typical physical traits:

Slim, lean physique
Narrow shoulders and small waist
Long limbs and fine bones
Very little body fat or muscle mass
Fast metabolism (find it hard to gain weight or build muscle)

Sheldon named this type after the ectoderm, the layer of cells in the embryo that develops into the skin, brain, and nervous system.

The Cerebrotonic Temperament

Sheldon believed that people with ectomorphic builds had what he called a Cerebrotonic temperament, meaning their personality was dominated by mental and nervous activity.

Ectomorphs are quiet, restrained, noon-assertive, sensitive, introverted, artistic, and self-conscious.

Common traits associated with cerebrotonic personalities:

Introverted and thoughtful – prefer quiet environments and mental work
Sensitive and self-aware – easily affected by stress or overstimulation
Socially reserved – may seem shy or withdrawn
Emotionally tense – often anxious, nervous, or self-conscious

In Sheldon’s theory, these individuals were seen as intellectual and introspective, but also fragile and high-strung due to their delicate nervous systems.

Sheldon’s “Extreme” Interpretations

In his more speculative writing, Sheldon associated extreme cerebrotonic traits with Hebephrenic schizophrenia, a withdrawn or dream-like state he called “oneirophrenia” (meaning “dream mind”).

He believed this was the result of imbalance or overstimulation of the nervous system — ideas that are no longer accepted in modern psychology.

2. Mesomorph (Somatotonic Temperament)

Physical Characteristics of Mesomorphs

Mesomorphs are characterised by strength, muscle, and balance.

Typical physical traits:

Muscular, athletic body
Broad shoulders and narrow waist
Well-proportioned build with low body fat
Naturally strong and physically capable
Good posture and quick, purposeful movements

Sheldon linked this type to the mesoderm, the middle embryonic layer that forms muscles, bones, and connective tissue.

The Somatotonic Temperament

Sheldon believed that people with a mesomorphic build had a Somatotonic temperament — a personality driven by action, confidence, and energy.

Typical traits of somatotonic personalities:

Energetic and active – always “on the go”
Assertive and confident – natural leaders, competitive, and bold
Adventurous – enjoy challenges and excitement
Tough and resilient – cope well with stress and physical demands

Sheldon viewed mesomorphs as decisive and ambitious, but sometimes aggressive or domineering.

Sheldon noted that the vast majority of criminal were mesomorphs. One explanation for this is that a solid muscular person becomes involved in crime at an early age due to their intimidating appearance.

3. Endomorph (Viscerotonic Temperament)

Endomorphs are characterized by increased fat storage, a wide waist, and a large bone structure.

Endomorphs, in everyday language, are fat. They have a smooth, round body, small shoulders, and shorter limbs.

Physical Characteristics of Ectomorphs

An endomorph is someone whose body is naturally soft, rounded, and fuller.

Typical physical features:

Rounder, softer body shape
Higher levels of body fat
Wider waist
Fat stored around the stomach, hips, and thighs
Curvier appearance (less muscular or slim)

Sheldon linked this body type to the endoderm — the inner layer of the embryo that forms internal organs like the stomach and intestines.

The Viscerotonic Temperament (Linked Personality Type)

Sheldon believed that body type was connected to temperament. For endomorphs, he proposed a personality type called viscerotonic.

Endomorphs (also known as viscerotonic) were seen as relaxed, sociable, tolerant, comfort-loving, peaceful, good-humored, and in need of affection.

Typical traits of the viscerotonic personality:

Sociable and friendly: Enjoys being around others and is often warm and affectionate
Relaxed and easygoing: Calm, tolerant, and not easily stressed
Comfort-seeking: Likes good food, pleasure, and relaxation
Emotionally warm: Often caring and supportive toward others

In Sheldon’s view, endomorphs tend to be content, cheerful, and good-natured, preferring comfort and companionship over competition or high activity.

Critical Evaluation

William H. Sheldon’s theory of Constitutional Psychology and his system of somatotypes (Endomorph, Mesomorph, and Ectomorph) have faced strong and lasting criticism.

Although Sheldon aimed to create a scientific link between body type and personality, his ideas have since been discredited in modern psychology.

Critics have raised concerns about his methods, scientific validity, and ideological bias, as well as the ethical implications of linking physical appearance to personality and worth.

1. Scientific and Methodological Problems

Subjective and Unreliable Measurements

Sheldon claimed to measure body types scientifically, but his system relied heavily on visual judgment and personal interpretation.

Lack of consistency: Results could vary widely depending on who made the assessment.
Measurement errors: Physical data like body fat or muscle size were often taken inconsistently.
Subjective scoring: Somatotype ratings (1–7 for each type) depended too much on personal opinion rather than objective data.

One of his former assistants, Barbara Honeyman Heath, accused Sheldon of manipulating data to fit his own ideas.

She alleged that he altered or edited photographs used in Atlas of Men to match predetermined body-type categories — raising serious doubts about the honesty of his research.

Oversimplified Psychology

Modern psychologists argue that Sheldon’s system reduces complex human behaviour to something far too simple.

Too deterministic: It suggests that people’s personalities are fixed by their body type, leaving little room for personal growth or environmental influence.
Lack of evidence: Later research found no reliable proof that body type predicts personality traits.
Ignoring other factors: Personality is now understood to result from a mix of genetics, environment, learning, and culture, not just physique.

2. Ideological and Ethical Concerns

Links to Eugenics and Prejudice

One of the most damaging criticisms of Sheldon’s work is its connection to eugenics and biological determinism — the idea that physical appearance reflects moral or intellectual worth.

Sheldon believed that beauty, health, and intelligence were biologically linked.
His writings included deeply prejudiced views, describing some ethnic groups and immigrants using offensive language.
Critics have compared his tone and thinking to Nazi ideology, which also valued physical “perfection” and promoted the idea of a biological hierarchy of human worth.

Psychologist Robert Holt went so far as to describe Sheldon’s work as “dangerously fascistic pseudo-science.”

After World War II, such ideas became widely condemned, and Sheldon’s reputation suffered as a result.

Stereotyping and Discrimination

Sheldon’s theory encouraged stereotyping based on body shape, leading to unfair and harmful assumptions.

For example:

Endomorphs were seen as lazy or self-indulgent.
Mesomorphs were viewed as aggressive or dominant.
Ectomorphs were labelled as shy or anxious.

These stereotypes can promote body shaming and reinforce social prejudice — issues still relevant in today’s culture.

3. Critiques from Other Disciplines

Criminology

Sheldon applied his somatotype theory to criminal behaviour in his book Varieties of Delinquent Youth (1949).

He claimed that muscular (mesomorphic) individuals were more likely to become delinquents.

However, leading criminologist Edwin Sutherland sharply criticised his research:

The data did not support Sheldon’s claims.
His sample of “delinquents” and “non-delinquents” was biased.
The study could not prove that any body type caused criminal behaviour.

Modern criminology instead focuses on social, environmental, and psychological factors, not physical appearance.

Conflict with Mainstream Psychology

Sheldon’s biological determinism clashed with the environmental and social focus of post-war psychology.

He rejected Freudian and behavioural explanations, believing instead that character came from genetic and physical inheritance — an idea that quickly fell out of favour in the more egalitarian, democratic climate of the 1950s.

4. Legacy and Modern Influence

Although Sheldon’s ideas about personality are now scientifically invalid, his system still holds historical significance.

Lasting influences:

Body classification: Sheldon’s somatotype system helped inspire later, more accurate ways of describing body composition.
Fitness and sports science: The terms endomorph, mesomorph, and ectomorph are still used today to categorise physique, not personality.
Early mind–body connection: Sheldon’s work represents one of the first serious (though flawed) attempts to study how the body and mind might be related.

Sheldon’s Study: Varieties of Delinquent Youth (1949)

William H. Sheldon’s Varieties of Delinquent Youth: An Introduction to Constitutional Psychiatry (1949) was the third book in his Human Constitution Series.

It was his most ambitious — and most controversial — attempt to apply his somatotype theory (body type classification) to human behaviour, especially to crime and delinquency.

1. Core Idea: The Muscular “Criminal Type”

The book’s main claim was that body type predicts a tendency toward criminal behaviour.

Sheldon focused particularly on the mesomorphic body type — muscular, strong, and athletic — and argued that this physique was more likely to be associated with delinquency and aggression.

The Mesomorph–Aggression Link

Sheldon compared photographs of criminals and non-criminals, concluding that muscular builds (mesomorphs) were most common among delinquents.
He connected this body type to what he called the Somatotonic temperament — energetic, assertive, and dominant.
He also placed the mesomorph in a psychiatric framework, linking it to paranoid schizophrenia and suggesting that “heroism and paranoia” could arise from the same temperament.

2. The “Heroic Delinquent” and the “Temperamental Superman”

Although Sheldon described the mesomorphic type as prone to delinquency, he also idealised certain muscular individuals as “biological heroes.”

He wrote about a “disturbing relationship between delinquency and heroism,” arguing that some delinquents showed admirable courage and defiance.
These “heroic types” were, in his words, “splendid physical specimens” who had been misunderstood by society and “forced underground into prisons and mental hospitals.”
Sheldon’s descriptions mixed science with almost poetic admiration — one mesomorphic youth was said to “walk the earth as a god who gazed serenely upon a swarming and inferior species.”
Despite this admiration, Sheldon criticised modern society’s obsession with muscle (“the Somatotonic Revolution”), claiming it represented anti-intellectualism and moral decay.

3. Ideological Foundations: Eugenics and Anti-Modernism

Varieties of Delinquent Youth was more than a criminological study — it was a manifesto for Sheldon’s eugenic worldview and his rejection of modern democratic and Freudian thought.

Eugenics and Biological Determinism

Sheldon believed that human worth and morality were biologically determined.

He argued that modern society was in decline because it allowed “bad reproduction to drive out good.”

Key ideas in his framework included:

“Irresponsible reproduction” (promiscuous breeding) as the highest form of delinquency.
Modern medicine and democracy were “keeping the weak alive indiscriminately,” leading to biological and moral degeneration.
His ultimate goal was a program he called “biological humanics” — a eugenic vision where obeying God meant obeying biological laws of selective breeding.

Prejudice and Fascist Overtones

The book contained explicit racist and anti-Semitic statements, including:

Referring to Jews and Italians as “vermin,”
Describing New York as “Negrophilic,”
And calling American culture “mongrel” and “socially chaotic.”

Critics immediately recognised these views as fascistic.

Psychologist Robert A. Holt, reviewing the book for the Rockefeller Foundation, called it a “piece of dangerously fascistic pseudo-science”, remarking that “the Buchenwald stench drifts from the pages.”

4. Rejection of Freudian Psychology

Sheldon also used the book to attack Freudian psychoanalysis, which dominated psychology at the time.

He dismissed Freudian ideas as “democratic and forgiving environmentalism”, claiming they excused weakness and avoided responsibility.
He described psychoanalysis as a “waster psychology” that encouraged comfort over discipline and lacked “noble values.”
In contrast, he promoted his constitutional psychology as a “hard science” rooted in biology and moral hierarchy.

dy and mind might be related.

The Gluecks’ Studies on Physique and Delinquency

The husband-and-wife research team Sheldon Glueck and Eleanor Glueck are best known for their large-scale studies of juvenile delinquency, which became milestones in criminological research.

Building on William H. Sheldon’s ideas about body type (somatotyping), they explored whether physical build, especially muscularity (mesomorphy), might be linked to criminal behaviour.

Their main works — Unraveling Juvenile Delinquency (1950) and Physique and Delinquency (1956) — reflected the positivist and multidimensional tradition in criminology.

1. Context and Research Design

The Gluecks aimed to better understand the causes of crime by using a rigorous, data-driven approach that included both biological and social variables.

While they were influenced by Sheldon’s ideas, they were far more scientific and cautious in their conclusions.

Adapting Sheldon’s Somatotypes

The Gluecks adopted Sheldon’s three-part body type system:

Endomorph – soft and round
Mesomorph – muscular and strong
Ectomorph – slim and fragile

Sheldon had claimed that mesomorphs were more likely to become delinquents because their muscular build was linked to energy and aggression.

The Gluecks took this idea and tested it more rigorously within a larger framework that also included psychological and social factors.

The Study: Unraveling Juvenile Delinquency (1950)

Their major research project compared 500 delinquent boys with 500 non-delinquent boys of similar backgrounds.

Each delinquent was matched case-by-case with a non-delinquent according to:

Age
Ethnicity
Intelligence
Socioeconomic status (neighbourhood and income)

This matching technique — similar to what modern researchers call Propensity Score Matching (PSM) — helped them isolate the effects of different variables on delinquency.

A Multifactor Approach

The Gluecks strongly rejected single-cause explanations for crime. Their study examined not just physique, but a wide range of influences:

67 personality traits, such as impulsivity and emotional control
42 sociocultural factors, including family relationships, school performance, and peer influence

Their goal was to understand how biology, psychology, and environment interact to shape behaviour.

2. Key Findings

The Gluecks’ findings supported part of Sheldon’s original claim but placed it in a much broader, non-deterministic context.

The Link Between Physique and Delinquency

Delinquents tended to have more muscular builds (mesomorphic) than non-delinquents.
However, the Gluecks did not argue that body type caused crime.
Instead, they proposed that biological traits (like strength or energy) may influence how individuals interact with their environment.
For example, stronger youths might be more likely to engage in physical risk-taking or attract certain peer groups.

Biological Context, Not Biological Destiny

Unlike Sheldon, the Gluecks saw physique as one factor among many.

They wrote that biological features “set the context for social forces”, rather than determine behaviour outright.
This made their theory more balanced and less deterministic than Sheldon’s biological approach.

3. Evaluation and Criticism

Despite their cautious and data-rich approach, the Gluecks’ inclusion of body type still drew sharp criticism — especially from sociologists who rejected biological explanations of crime.

The Sutherland–Glueck Debate

The most prominent critic was Edwin H. Sutherland, a leading sociological criminologist best known for his Differential Association Theory (which argued that crime is learned through social interaction).

Sutherland’s stance: Crime should be explained purely through social factors, not biology or individual traits.
He viewed the Gluecks’ work — which included physique, intelligence, and personality — as a threat to the sociological focus of criminology.
Sutherland accused them of using “scanty data” and called their conclusions “methodologically unsound” and “invalid.”
As a result, many sociologists dismissed the Gluecks’ research as belonging to the same tradition as Sheldon’s and other “biological determinists,” even though the Gluecks themselves criticised Sheldon’s methods for being unscientific and biased.

The Gluecks’ Response

The Gluecks defended their approach, emphasizing that:

Their work was multifactorial, not biological determinism.
Their findings were based on carefully matched samples and statistical analysis.
They saw crime as a product of interacting causes — biological predispositions, psychological traits, and environmental pressures.

References

Bannister, R. (1979). Sociology and Scientism: The American Quest for Objectivity, 1880–1940. University of North Carolina Press.

Glueck, E., & Glueck, S. (1950). Unraveling Juvenile Delinquency. Harvard University Press.

Glueck, S., & Glueck, E. (1956). Physique and Delinquency. Harper & Brothers.

Holt, R. R. (1949, December 10). Letter to the editor regarding Varieties of Delinquent Youth. New York Times Book Review.

Laub, J. H., & Sampson, R. J. (1991). The Sutherland–Glueck debate: On the sociology of criminological knowledge. American Journal of Sociology, 96(6), 1402–1440.

Sheldon, W. H. (1940). The Varieties of Temperament: A Psychology of Constitutional Differences. Harper & Brothers.

Sheldon, W. H. (1942). The Varieties of Human Physique: An Introduction to Constitutional Psychology. Harper & Brothers.

Sheldon, W. H. (1949). Varieties of Delinquent Youth: An Introduction to Constitutional Psychiatry. Harper & Brothers.

Sheldon, W. H. (1954). Atlas of Men: A Guide for Somatotyping the Adult Male at All Ages. Harper & Brothers.

Sheldon, W. H., & Stevens, S. S. (1942). The constitutional and temperamental factors in personality. Psychological Review, 49(2), 85–127.

Sutherland, E. H. (1947). Principles of Criminology (4th ed.). J. B. Lippincott Company.

Walters, R. (1991). The American Eugenics Movement and the Development of Criminological Thought. In Rafter, N. H. (Ed.), Creating Born Criminals: Biological Theories of Crime and Their Legacy. University of Illinois Press.

Weiner, D. B. (1989). William Herbert Sheldon, the Varieties of Human Physique, and American Eugenics: A Historical Reappraisal. Journal of the History of the Behavioral Sciences, 25(3), 235–257.