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The New York Longitudinal Study
Alexander Thomas, Stella Chess, Herbert G. Birch
personality types - temperament traits

Thomas, Chess & Birch ~
human personality traits

The New York Longitudinal Study, started in 1956 and continued over several decades thereafter, is regarded as a classic study into personality types and temperament traits.
The study, conducted amongst young children, in its early days had such persons as Alexander Thomas, Stella Chess, Herbert G. Birch and Margaret Hertzig as principal contributors.

The New York Longitudinal Study investigations included direct observation and also interviews with parents about their children.
The team came up with ways of investigating individual styles of personality and temperament amongst children and discovered ways of identifying and giving a relevant rating to nine separate "qualities" associated with personality and temperament.

In analysing their data, the nine characteristics that were identified by the team as being reliably scorable on a three-point scale (medium, high and low) were:-
  1. the level and extent of motor activity;

  2. the rhythmicity, or degree of regularity, of functions such as eating, elimination and the cycle of sleeping and wakefulness;

  3. the response to a new object or person, in terms of whether the child accepts the new experience or withdraws from it;

  4. the adaptability of behavior to changes in the environment;

  5. the threshold, or sensitivity, to stimuli;

  6. the intensity, or energy level, of responses;

  7. the child's general mood or "disposition", whether cheerful or given to crying, pleasant or cranky, friendly or unfriendly;

  8. the degree of the child's distractibility from what he is doing;

  9. the span of the child's attention and his persistence in an activity.

The set of ratings in these nine characteristics were held to define the temperament, or behavioural profile, of each child. Such profiling was held to be reliable even as early as the age of two or three months. The team found that the nine qualities could be identified and rated in a wide diversity of population samples they studied: be they rich, poor, of recent immigrant background, mentally retarded children, children born prematurely or children with congenital rubella ("German measles") related conditions the team were satisfied that they could reliably rate these nine personality / temperament characteristics.

When the researchers analysed the behavioural profiles of the children in an endeavour to find correlations among the nine individual characteristics, they found that certain attributes did seem to cluster together. This clustering seemed to point toward the definition of three general types of temperament (although quite a few of the children did not easily fit into any of these three "types").
The "easy children"
This type - approximately forty per cent of the 141 children in the total sample were placed in this category - was held to be characterised by positiveness in mood, regularity in bodily functions, a low or moderated intensity of reaction, adaptability and positive approach to, rather than withdrawal from, new situations.
In infancy these children seemed to quickly establish regular sleeping and feeding schedules, were generally cheerful and adapted quickly to new routines, new food and new people. As they grew older they learned the rules of new games quickly, participated readily in new activities and adapted easily to school. This group was called the "easy children", because they presented so few problems in care and training.

The "difficult children"
Another set of characteristics such as irregular in bodily functions, usual intensity in reactions, tendency to withdraw in the face of new stimuli, relative slowness to adapt to changes in the environment and general negativity in mood was deemed by the reseachers to be associable with another group that they labelled "difficult children".
As infants such children - comprising about ten per cent of the children sampled - were often irregular in feeding and sleeping, were slower to accept new foods, took a longer time to adjust to new routines or activities and tended to cry a great deal. Their crying and their laughter were rated as being characteristically loud. Frustrations usually seemed to send them into violent tantrums. These children were, of course, something of a trial to their parents and required a high degree of consistency and tolerance in their upbringing.

The "slow to warm up"
The children classified by the team as "slow to warm up" - fifteen per cent of the population sample studied - typically had relatively low activity levels, tended to withdraw on their first exposure to new stimuli, were slower to adapt, were somewhat negative in mood and responded to situations with a low intensity of reaction.
With some forty per cent being deemed to be "easy children", some ten per cent being deemed to be "difficult children", and with some fifteen per cent being deemed to be "slow to warm up" only some sixty-five per cent of the children were described as belonging to one or other of the three categories the study felt it appropriate to to define.
The remaining thirty-five per cent had such mixtures of the nine temperament traits as did not seem to allow classification into one of the three groups.

Earlier publications of the findings of the New York Longitudinal Study include:-

Thomas A, Chess S: An approach to the study of sources of individual difference in child behavior. J Clin Exp Psychopathol 1957; 18:347-357

Chess S, Thomas A, Birch HG, Hertzig M: Implications of a longitudinal study of child development for child psychiatry. Am J Psychiatry 1960; 117:434-441

see also:-

Your Child Is A Person: A Psychological Approach To Childhood Without Guilt. The Viking Press, New York: 1965. 213 pages


The Origin of Personality. Scientific American, pp 102-109. 1970


Temperament: Theory and Practice by S. Chess and A. Thomas

There may well be an association to be made between the New York Longitudinal Study and the work of Dr.William Sheldon who also researched into Human personality traits / temperament types.

Some inkling of the potential far-reaching implications of the research by the New York Longitudinal Study and by Dr. Sheldon into human personality and temperament traits can be gained through reading our page about the " Tripartite Soul " of Humanity as identified by Plato and Socrates, by Pythagoras, by Shakespeare and by several Major World Religions:-

The " Tripartite Soul "
view of Human Nature