Temperament and Neoteny / Temple Grandin

Behavioral Genetics and Animal Science

TEMPLE GRANDIN AND MARK J. DEESING  http://www.grandin.com/references/genetics.html (full text)

Department of Animal Science, Colorado State University, Fort Collins, Colorado Genetics and the Behavior of Domestic Animals (Chapter One) Academic Press 1998, San Diego, California

Link to post covering previous material from the book: https://aspergerhuman.wordpress.com/2015/12/03/domestication-neoteny-and-behavior-grandin/

I’m deleting some text for length and to highlight information that may be important to understanding Asperger behavior.

Genetic Factors and the Need for Novelty

In mammals and birds, normal development of the brain and sense organs requires novelty and varied sensory input. Nobel prize winning research of Hubel and Wiesel (1970) showed that the visual system is permanently damaged if kittens do not receive varied visual input during development. When dogs are raised in barren and nonstimulating environments they are also more excitable (Walsh and Cummins, 1975; Melzak and Burns, 1965). Schultz (1965) stated, “when stimulus variation is restricted central regulation of threshold sensitivities will function to lower sensory thresholds.” Krushinski (1960) studied the influence of isolated conditions of rearing on the development of passive defense reactions (fearful aggression) in dogs and found that the expression of a well-marked fear reaction depends on the genotype of the animal. […] In general, animals reared in isolation become more sensitive to sensory stimulation because the nervous system attempts to readjust for the previous lack of stimulation.

[…] chicks from a flighty genetic line were more likely to panic when a novel ball was placed in their pen, but they were also more attracted to a novel food than birds from a calm line. […] rats bred to be dull greatly improved in maze learning when housed in a cage with many different objects; however, enriched environments had little effect on the rats bred for high intelligence. […] rearing rats in an environment with many novel objects improves learning and resulted in increased growth of dendrites, which are nerve endings in the brain.

Piglets allowed to choose between a familiar object and a novel object prefer the novel object […] The first author has observed that nervous, excitable hybrid pigs often chew and bite vigorously on boots or coveralls. This behavior is less common in placid genetic lines of pigs. Although hybrid pigs are highly attracted to novelty, tossing a novel object into their pen will initially cause a strong flight response. […] Denied variety and novelty in their environments, highly reactive animals adapt poorly when compared to animals from calmer genetic lines

In summary, in both wild and domestic animals novelty is both highly feared and necessary. Novelty is most desirable when animals can approach it slowly. Unfortunately, novelty is also fear-provoking when animals are suddenly confronted with it.


In animals as diverse as rats, chickens, cattle, pigs, and humans, genetic factors influence differences in temperament. […] Some individuals are wary and fearful and others are calm and placid. Boissy (1995) stated, fearfulness is a basic psychological characteristic of the individual that predisposes it to perceive and react in a similar manner to a wide range of potentially frightening events. In all animals, genetic factors influence reactions to situations which cause fear […] therefore, temperament is partially determined by an individual animal’s fear response. […] Plomin and Daniels (1987) found a substantial genetic influence on shyness (fearfulness) in human children. Shy behavior in novel situations is considered a stable psychological characteristic of certain individuals. […]

In an experiment designed to control for maternal effects on temperament and emotionality […] showed that maternal effects were not great enough to completely mask the temperament differences […] In extensive review of the literature, Broadhurst (1975) examined the role of heredity in the formation of behavior and found that differences in temperament between rats persist when the animals are all raised in the same environment.

Measuring Fear-Based Behaviors

One method of testing fearfulness is the open field test (Hall, 1934). Sudden placement of an animal in an open field test arena is used to measure differences in fearfulness. Open field testing has shown differences in fearfulness between different genetic lines of animals. The test arena floor is usually marked in a grid to measure how much the animals walk around and explore. Huck and Price (1975) showed that domestic rats are less fearful and will walk round the open field more than wild rats. Price and Loomis (1973) explained that some genetic strains of rats are less fearful and explore an open field arena more than others. Eysenck and Broadhurst (1964) found that rodents with high emotional reactivity are more fearful and explore the open field less compared to placid genetic lines.


Mahut (1958) demonstrated an example of differences in fear responses between beagles and terriers. When frightened, beagles freeze and terriers run around frantically In domestic livestock, measuring fear reactions during restraint or in an open field test has revealed differences in temperament both between breeds and between individuals within a breed (Grandin, 1993a; Tulloh, 1961; Dantzer and Mormede, 1983; Murphey et al., 1980b, 1981). The fearful, flighty animals become more agitated and struggle more violently when restrained for vaccinations and other procedures (Fordyce et al., 1988; Grandin, 1993a). Fear is likely to be the main cause of agitation during restraint in cattle, horses, pigs, and chickens. Genetic effects on behavior during transport, handling, and restraint of these animals are further discussed in Chapter 4.

Species Differences in Fear Reactions

In an open field test, frightened rodents often stay close to the arena walls, whereas frightened cattle may run around wildly and attempt to escape. Rodents stay close to the walls because they naturally fear open spaces, whereas cattle run around wildly because they fear separation from the herd. This is an example of differences between species in their response to a similar fear- provoking situation. Fear can be manifested in many different ways. For example, a frightened animal may run around frantically and try to escape in one situation, while in another situation the same animal may freeze or limit its movement. Chickens often freeze when handled by humans. Jones (1984) called this “tonic immobility.” The chickens become so frightened that they cannot move. Forceful capture of wild animals can sometimes inflict fatal heart damage. Wildlife biologists call this capture myopathy In summary, much is known about the complex phenomenon of fear, but many questions still remain.


Genetics influences the intensity of fear reactions. Genetic factors can also greatly reduce or increase fear reaction in domestic animals (Price, 1984; Parsons, 1988; Flint et al., 1995). Research in humans has clearly revealed some of the genetic mechanisms which govern the inheritance of anxiety (Lesch et al., 1996). LeDoux (1992) and Rogan and LeDoux (1996) state that all vertebrates can be fear-conditioned. Davis (1992) recently reviewed studies on the biological basis of fear. Overwhelming evidence points to the amygdala as the fear center in the brain. A small bilateral structure located in the limbic system, the amygdala is where the triggers for flight or fight” are located. Electrical stimulation of the amygdala is known to increase stress hormones in rats and cats (Matheson et al., 1971; Setckleiv et al., 1961); destroying the amygdala can make a wild rat tame and reduce its emotionality (Kemble et al., 1984). Destroying the amygdala also makes it impossible to provoke a fear response in animals (Davis, 1992). Blanchard and Blanchard (1972) showed that rats lose all of their fear of cats when the amygdala is lesioned. Furthermore, when a rat learns that a signal light means an impending electric shock, a normal response is to freeze. Destroying the amygdala will eliminate this response (Blanchard and Blanchard, 1972; LeDoux et al., 1988, 1990). Finally, electrical stimulation of the amygdala makes humans feel fearful (Gloor et al., 1981). Animal studies also show that stimulation of the amygdala triggers a pattern of responses from the autonomic nervous system similar to that found in humans when they feel fear (Davis, 1992).

Heart rate, blood pressure, and respiration also change in animals when the flight or fight response is activated (Manuck and Schaefer, 1978). All these autonomic functions have neural circuits to the amygdala. Fear can be measured in animals by recording changes in autonomic activity In humans, Manuck and Schaefer (1978) found tremendous differences in cardiovascular reactivity in response to stress, reflecting a stable genetic characteristic of individuals.

Fearfulness and Instinct

Fearfulness and instinct can conflict. This principle was observed firsthand by the second author during his experience raising Queensland Blue Heeler dogs. Annie’s first litter was a completely novel experience because she had never observed another dog giving birth or nursing pups. She was clearly frightened when the first pup was born and it was obvious that she did not know what the pup was; however, as soon as she smelled it her maternal instinct took over and a constant uncontrollable licking began. Two years later, Annie’s daughter Kay had her first litter. Kay was more fearful than her mother and her highly nervous temperament overrode her innate licking program. When each pup was born Kay ran wildly around the room and would not go near them. The second author had to intervene and place the pups under Kay’s nose; otherwise, they may have died. Kay’s nervous temperament and fearfulness were a stronger motivation than her motherly instinct.


Raising young animals in barren environments devoid of variety and sensory stimulation will have an effect on development of the nervous system. It can cause an animal to be more reactive and excitable when it becomes an adult. This is a long-lasting, environmentally induced change in how the nervous system reacts to various stimuli. Effects of deprivation during early development are also relatively permanent. Melzak and Burns (1965) found that puppies raised in barren kennels developed into hyperexcitable adults. In one experiment the deprived dogs reacted with ~diffuse excitement” and ran around a room more than control dogs raised in homes by people. Presenting novel objects to the deprived dogs also resulted in diffuse excitement.” Furthermore, the EEGs of the kennel-raised dogs remained abnormal even after they were removed from the kennel (Melzak and Burns, 1965). Simons and Land (1987) showed that the somatosensory cortex in the brains of baby rats will not develop normally if sensory input was eliminated by trimming their whiskers. A lack of sensory input made the brain hypersensitive to stimulation. The effects persisted even after the whiskers had grown back.

Development of emotional reactivity of the nervous system begins during early gestation. Denenberg and Whimbey (1968) showed that handling a pregnant rat can cause her offspring to be more emotional and explore less in an Open field compared to control animals. This experiment is significant because it shows that handling the pregnant mother had the opposite effect on the behavior of the infant pups. Handling and possibly stressing the pregnant mothers changed the hormonal environment of the fetus which resulted in nervous offspring. However, handling newborn rats by briefly picking them up and setting them in a container reduced emotional reactivity when the rats became adults (Denenberg and Whimbey 1968). The handled rats developed a calmer temperament.

The adrenal glands are known to have an effect on behavior (Fuller and Thompson, 1978). The inner portions of the adrenals secrete the hormones adrenaline and noradrenaline, while the outer cortex secretes the gender hormones androgens and oestrogens (reproductive hormones), and various corticosteroids (stress hormones). Yeakel and Rhoades (1941) found that Hall’s (1938) emotional rats had larger adrenals and thyroids compared to the nonemotional rats. Richter (1952, 1954) found a decrease in the size of the adrenal glands in Norway rats accompanied by domestication. Several line and strain differences have been found since these early reports. Furthermore, Levine (1968) and Levine et al. (1967) showed that brief handling of baby rats reduces the response of the adrenal gland to stress. Denenberg et al. (1967) concluded that early handling may lead to major changes in the neuroendocrine system.

Changing Reactivity versus Taming

Adult wild rats can be tamed and become accustomed to handling by people (Galef, 1970). This is strictly learned behavior. Taming full-grown wild animals to become accustomed to handling by people will not diminish their response to a sudden novel stimulus. This principle was demonstrated by Grandin et al. (1994) in training wild antelope at the Denver Zoo for low- stress blood testing. Nyala are African antelope with a hair-trigger flight response used to escape from predators. During handling in zoos for veterinary treatments, nyala are often highly stressed and sometimes panic and injure themselves. Over a period of 3 months, Grandin et al. (1995) trained nyala to enter a box and stand quietly for blood tests while being fed treats. Each new step in the training had to be done slowly and carefully Ten days were required to habituate the nyala to the sound of the doors on the box being closed.

All the training and petting by zoo keepers did not change the nyala’s response to a sudden, novel stimulus. […]

Domestic versus Wild

Wild herding species show much stronger fear responses to sudden novelty compared to domestic ruminants such as cattle and sheep. Domestic ruminants have attenuated flight responses due to years of selective breeding (Price, 1984). Wild ruminants will learn to adapt in captivity and associate people with food, but when frightened by some novel stimulus they are more likely to panic and injure themselves (Grandin, 1993b, 1997) […] In summary, experience can affect behavior in two basic ways: by conventional learning or by changing nervous system reactivity Most importantly, environmental conditions (enriched versus barren) have the greatest effect on the nervous systems of young animals.


Neoteny is the retention of the juvenile features in an adult animal. Genetic factors influence the degree of neoteny in individuals. Neoteny is manifested both behaviorally and physically In the forward to “The Wild Canids” (Fox, 1975), Conrad Lorenz adds a few of his observations on neoteny and the problems of domestication: “The problems of domestication have been an obsession with me for many years. On the one hand I am convinced that man owes the life-long persistence of his constitutive curiosity and explorative playfulness to a partial neoteny which is indubitably a consequence of domestication In a curiously analogous manner does the domestic dog owe its permanent attachment to its master to a behavioral neoteny that prevents it from ever wanting to be a pack leader On the other hand, domestication is apt to cause an equally alarming disintegration of valuable behavioral traits and an equally alarming exaggeration of less desirable ones.”

Infantile characteristics in domestic animals are discussed by Price (1984), Lambooij and van Putten (1993), Coppinger and Coppinger (1993), Coppinger and Scheider (1993), and Coppinger et al. (1987). The shortened muzzle in dogs and pigs is an example. Domestic animals have been selected for a juvenile head shape, shortened muzzles, and other features (Coppinger and Smith, 1983). Furthermore, retaining juvenile traits makes animals more tractable and easy to handle. The physical changes are also related to changes in behavior.



Countless examples of serious problems caused by continuous selection for a single trait can be found in the medical literature (Steinberg et al., 1994; Dykman et al., 1969). People with experience in animal husbandry know that overselection for single traits can ruin animals. Good dog breeders know this. Sometimes traits that appear to be unrelated are in fact linked. Wright (1922, 1978) demonstrated this clearly by continuous selection for hair color and hair patterns in inbred strains of guinea pigs. Depressed reproduction resulted in all the strains. Furthermore, differences in temperament, body conformation, and the size and shape of internal organs were found. Belyaev (1979) further showed that continuous selection for a calm temperament in foxes resulted in negative effects on maternal behavior and neurological problems. The fox experiments also found graded changes in many traits over several years of continuous selection for tame behavior. Physiological and behavioral problems increased with each successive generation. In fact, some of the tamest foxes developed abnormal maternal behavior and cannibalized their pups. Belyaev et al. (1981) called this “destabilizing selection,” in contrast to “stabilizing selection” found in nature (Dobzhansky 1970; Gould, 1977).

There are also countless examples in the veterinary medical literature of abnormal bone structure and other physiological defects caused by overselecting for appearance traits in dog breeds (Ott, 1996). The abnormalities range from bulldogs with breathing problems to German shepherds with hip problems. Scott and Fuller (1965) reported the negative effects of continuous selection for a certain head shape in cocker spaniels:

[…] Cocker spaniels are selected for a broad forehead with prominent eyes and a pronounced “stop,” or angle, between the nose and forehead. When we examined the brains of some of these animals during autopsy, we found that they showed a mild degree of hydroencephaly; that is, in selecting for skull shape, the breeders accidentally selected for a brain defect in some individuals. Besides all this, in most of our strains only about 50 percent of the females were capable of rearing normal, healthy litters, even under nearly ideal conditions of care.

Links between Different Traits

Casual observations by the first author also indicate that the most excitable, flighty pigs and cattle have a long, slender body with fine bones. Some of the lean hybrid pigs have weak legs and a few of the normally brown-eyed pigs now have blue eyes. Blue eyes are often associated with neurological problems (Bergsma and Brown, 1971; Schaible, 1963). Furthermore, pigs and cattle with large, bulging muscles often have a calmer temperament than lean animals with less muscle definition. However, animals with the muscle hypertrophy trait (double muscling) have a more excitable temperament (Holmes et al., 1972). Double muscling is extreme abnormal muscling and it might have the opposite effect on temperament compared to normal muscling.

Another example of apparently unrelated traits being linked is deafness in dogs of the pointer breed selected for nervousness (Kllen et al., 1987, 1988). There appears to be a relationship between thermoregulation and aggressiveness. Wild mice selected for aggressiveness used larger amounts of cotton to build their nests than mice selected for low aggression (Sinyter et al., 1995). This effect occurred in both laboratory and wild Strains of mice.

Researchers using high-tech “knockout” gene procedures have been frustrated by the complexity of genetic interactions. In this procedure, genes are knocked out in a gene-targeting procedure whereby a gene is prevented from performing its normal function. The knockout experiments have shown that blocking different genes can have unexpected effects on behavior. In one experiment, superaggressive mice were created when genes involved with learning were inactivated (Chen et al., 1994). The mutant mice had little or no fear and fought until they broke their backs. […] disabled the gene that produces enkephalin (a brain opioid substance) and found unexpected results. Enkephalin is a substance normally involved in pain perception; however, the mice that were deficient in this substance were very nervous and anxious. They ran frantically around their cages in response to noise. The bottom line conclusion from several different knockout experiments is that changing one gene has unexpected effects on other systems. Traits are linked, and it may be impossible to completely isolate single gene effects. Researchers warn that one must be careful not to jump to a conclusion that they have found an “aggression gene” or a “maternal gene” or an “anxiety gene.” […]

Twenty years ago behavioral geneticists concluded that the inheritance of behavior is complex. Fuller and Thompson (1978) concluded, “It has been found repeatedly that no one genetic mechanism accounts exclusively for a particular kind of behavior.

Random Factors

Gartner (1990) concluded that up to 90% of the cause of random variability cannot be explained by differences in the animals’ physical environment. In both mice and cattle, random factors affected body weights. Gartner (1990) believes that the random factors may have their influence either before or shortly after fertilization.

The interactions between environmental and genetic factors are complex. Both an animals’ genetic makeup and its environment determine how it will behave. In subsequent chapters in this book the interactions of genetics and environment will be discussed in greater detail. Genetics has profound effects on an animal’s behavior.


There is a complex interaction between genetic and environmental factors which determines how an animal will behave. The animal’s temperament is influenced by both genetics and learning. Another principle is that changes in one trait, such as temperament, can have unexpected effects on other apparently unrelated traits. Overselection for a single trait may result in undesirable changes in other behavioral and physical traits.

I think we can put to rest the idea that “normal” (as a prescriptive and measurable conformity put forth by psychological dogma) exists in humans.


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