EMOTIONAL, AND SOCIAL DEVELOPMENT OF THE YOUNG DOG
Dr. Joël Dehasse, Behaviorist Veterinarian www.joeldehasse.com
Version 1.1 - 6 Feb.97
Dr. Joël Dehasse
3 ave du Cosmonaute
1150 Brussels - Belgium
This article has
been published extensively, with images and charts, in The
Bulletin for Veterinary Clinical Ethology,
Vol.2, n°1-2, pp 6-29, 1994 (Brussels) and is in its original
format on the author's website at http://www.joeldehasse.com/a-english/puppy-ima.html
main phases in neurological development
concept of sensitive period
emotional self-regulation (homeostasis) phase
precocious learning-conditioning phase
cognitive sensitization-rationalization in pre-puberty
In our Western
culture, the relation between humans and dogs is played out in a
historical and socio-economic context that fosters the emergence of
behavioral dysfunctions in animals (the discrepancy between the
imagined dog and reality). Many
behavioral problems in dogs arise from a failure to recognize social
and environmental constraints during their growth.
In this article we shall briefly trace these phases of a dog's
social and behavioral ontogeny and epigenesis. We shall also point
risk factors that
can undermine the harmonious interaction between humans and their dogs.
Main Phases in Neurological Development
Like humans, dogs
belong to a species that matures slowly after birth: the new-born is
not completely developed and is incapable of surviving on its own.
This implies a structured and caring parental environment (caring for
the young), reflexes that orient the young puppy to its parents, and
the existence of optimal, even crucial, periods in the development of
the animal's nervous system.
the nervous system underlies behavioral epigenesis. The immaturity
of the nervous system at birth is obvious: Cragg (1975) calculated
that in cats the number of synapses per cortical neuron grows from a
few hundred to nearly 12,000 in the 10th to 35th day after birth (in
Changeux, 1983). Various measurements (volume, weight, percentage of
dry matter, oxygen consumption) of the brain show that growth is
rapid until the 6-7th week when development suddenly slackens
considerably. The number of brain cells and their myelination reaches
full adult maturity at 4 weeks. It is worth mentioning that the brain
is totally unmyelinated at birth, except for the trigeminal nerve and
the non-acoustic part of the auditory nerve which correspond to the
new-born's orientation reflexes (Herman 1958, in Scott & Fuller
1965). The motor cortex is the more developed at birth. The occipital
cortex, however, then grows more rapidly than the motor and frontal
lobes; it also contains several immature neuroblasts that reach full
development only around 3 weeks of age (Fox, 1965).
epigenesis (ethogenesis) is linked to the way neuronal connections
The development of the neuronal networks is a characteristic
process: "the phase of synaptic redundancy followed by a phase
of regression in the axonal and dendritic branches is a critical
period of development... The redundancy is temporary. Active nerve
endings are eliminated all the while the nervous system itself is
neuronal hecatomb is part of the normal development.
... The hypothesis that spontaneous, and later evoked, nervous
activity contributes to the development of neural networks and
synapses appears to be plausible" (Changeux, 1983).
epigenesis is influenced by environmental
factors, by the surroundings.
regulates neuronal development.
In a now classic experiment (by Weisel and Hubel from 1963, in
Changeux 1983) with monkeys, noticeable visual defects were caused
when one eye was sewn shut during the first six weeks of life; the
problems were reversible if the eye was re-opened after three weeks'
time. The same experiment on adult monkeys showed no effect on
vision. Similar experiments on cats show there is a sensitive period
for visual development between 3 and 7 weeks of age, and incapacity
to recover vision after three months (Weisel and Hubel, in Vastrade,
1987). "There is a critical period during which the abnormal
functioning of a system causes irreversible lesions." (Changeux,
1983). According to Klosovskii (1963), puppies and kittens that
undergo periods of forced rotation for several days have vestibular
neurons that are larger than those of animals that have not received
this stimulus (in Fox: 1965).
postnatal temporary occlusion of the ears leads to subsequent
difficulties to locate sounds in space and to reduction of
discrimination of auditive patterns (Caston: 1993). In rodents
always, precocious exposition to other species odors eases future
interspecific socialization (decrease in aggressions, lowering of
corticosteroïds hormones) (Caston: 1993).
* This reflects
Cyrulnik's (1991) remarks that the
brain becomes atrophied when [an animal] is raised in sensorial isolation,
and it develops
more than average in an environment of hyperstimulation
in noise, affectivity, odors, tastes, sight, etc....
studies have showed that prolonged
precocious isolation was responsible for long-lasting structural or
functional cerebral modifications.
Isolation leads to a diminution of the dendritic network in the
monkey frontal cortex; it also induces a reversible diminution of the
activity of the mesocorticofrontal dopaminergic pathways (with
hyperreactivity to stress), associated with a slight increase of the
activity of the mesolimbic and nigrostriatal dopaminergic pathways
(Verdoux and Bourgeois: 1991).
seems to come about in stages;
these stages are possibly nothing more than a "simplified
classification system where the classifier traces a straight line
through a continuum" (Bateson, 1981). Pampiglione (1963)
observed marked changes in EEG patterns at 7-8 days, 5-6 weeks
(reaching adult levels), and 4-5 months (Fox, 1965). According to
Charles and Fuller (1956) (in Scott and Fuller: 1965) the alpha
rhythm that appears at 21 days signals an activation of the sense of
sight. Scott (1958, 1962) (in Scott and Fuller: 1965, and Fox: 1965)
speaks of several stages of neurological, reflexive and behavioral
development that are particularly didactic:
neonatal (0-14 days), transitional (14-21 days, starting when the
eyes open and ending when the animal starts on hearing a noise),
socialization (21-70 days) and juvenile (70 days and older). These
periods overlap considerably. Since these stages are still used in
the literature, they are worth mentioning. We recommend reading
Vastrade (1986), Markwell & Thorne (1987), and Nott (1992) for an
overview, or Scott and Fuller (1965) or Fox (1965) for a more
behavioral patterns develop over successive phases, according to
internal and external factors that interact in a complex and
continuous manner. As Cyrulnik wrote, "the World of each animal
is built around the double constraint of genetics and development".
Concept of Sensitive Periods
Bateson (1981) has
described the developing individual as a train with its windows
closed - at a certain point (maturing) the windows open and the
traveler is encouraged to study the information passing by outside.
Depending on the information presented (learning), he/she either
continues (motivation) or stops (habituation, impregnation, or
self-limitation) looking out the open window. In other cases the
windows close when a new point is reached.
This notion of
learning in phases has various names: sensitive period, critical
moment, optimal period, vulnerable point, crucial stage, susceptible
period, and so on.
is a point in the maturing process when events are susceptible to
leaving long-term effects, or a period when learning is easier and
knowledge gained is stored in the long-term memory. During
the sensitive period, a small number of determining experiences have
major effects (or damages) on future behavior. The
sensitive period is preceded and followed by periods of lower
sensitivity, and the transition is gradual.
The notion of
sensitive period is used in the place of critical period because the
former extends over a longer period of time. Ducklings become
attached to their mother between the 13th and 16th hour of life (Hess
1959, in Cyrulnik 1989), it takes 5 minutes of contact during the
first hour after birth for a she-goat to become attached to the odor
of her kid (Bateson, 1981), and a ewe needs contact within 4 hours
after the birth of her lamb. Without this contact the mother will
reject her young in the last two cases (Collias, 1956, in Scott and
Fuller, 1965). These very short periods justify the term critical.
Since puppies do not have such short periods of facilitated
learning, we will use the term sensitive period.
I was one of the
people who helped spread this concept in French-speaking countries
(Dehasse and De Buyser: 1983, 1989, 1991) by emphasizing on several
occasions that the sensitive period in the behavioral epigenesis in
puppies extended from 3
weeks to 3 months
of age. The duration of this sensitive period had to be verified by
delving into the literature on experiments in this realm and clinical review.
Pregnant rats that
have been placed under stress or injected with ACTH or adrenaline
give birth to young rats that are emotive and perform less well than
a control group. (These young rats are raised by another mother that
has not been placed under stress to preclude the possibility of
postnatal maternal influence.) (Fox, 1978)
In a similar vein,
when a pregnant animal is petted her litter is more docile (Denenberg
and Whimbey 1963, in Fox 1978). This effect, called the
"gentling", "petting" or "caress"
effect, can be prolonged by caresses to the new-born. According to
Fox (1975, in Fox 1978) this activates the parasympathetic system,
facilitating relaxation, digestion and emotional attachment,
and thus socialization as well. Experiments by Cyrulnik with cats
have shown that attachment depends on the cholinergic system;
anti-cholinergics block the attachment process. The object of
attachment is a being whose presence soothes and whose absence causes
distress, who possess the signs of familiarization; a "reference
being" (Eibl-Eibesfeldt 1984). This is probably linked to the
social species' innate need for contact.
A dog's tactile
capacities develop before birth, and it is possible that it already
becomes used to contact in the uterus, when the mother is petted.
Puppies manipulated this way show a greater tolerance to touching
than dogs born of a mother who was not petted.
In rats, once
again, manipulation (contact, exposure to cold, etc.) at a young age
or before birth (manipulation of the pregnant mother) gives greater
resistance to stress (cold, hunger) and disease (implanted tumors).
This phenotypical effect is transmitted non-genetically for several
generations (Denenberg and Rosenberg, in Fox 1978).
enable us to deduce that when a gestating pet is given a friendly and
caring human environment (with affectionate physical contact), the
domestication and emotional balance of her offspring is facilitated,
as compared with an environment where there is no contact and
interaction with people.
We will only say a
few words about this period, which arbitrarily ranges from birth to
the opening of the eyes at approximately 13 days.
limited observation of the new-born puppy could lead one to believe
it did not even belong to the canine species: awkward, dragging
itself around, oriented to contact, the mother's teats and the smell
of milk, yapping in distress when isolated, cold, hungry or in pain,
and having only a limited capacity to keep itself warm and to learn.
The new-born puppy is a completely dependent being, and apparently
hardly influenceable psychologically in classical conditioning tests.
As such this phase holds only minor interest in our study.
It is possible,
however, that the future holds surprising discoveries about the
epigenetic importance of this neonatal period, especially as concerns
the "manipulation" effect on neuro-hormonal development.
At birth the puppy
has not an innate recognition of members of its species; in a way it
does not know it is a dog. This must be learned!
identification a puppy is able to recognize its parents (filial
and develop preferential intraspecific social relations (fraternal
and the relations (sexual
which mean the survival of the species (filial and sexual
imprinting). An animal that is badly imprinted is lost for the species.
Here are a few examples:
Christy, a female
puppy, was raised in complete isolation from other dogs by the
"colony" of students at the Jackson Laboratory. At 9 weeks
she was introduced to other dogs: the adults growled at her but
showed no further signs of aggression and the puppies (litter-mates)
began to play-fight and she responded. In 4 days time her behavior
was indistinguishable from that of the other puppies (Scott and
Note that, unlike
goats and sheep, adult dogs show no parental rejection of their young!
A fox terrier
puppy (male) raised in complete isolation and introduced to other
dogs at 16 weeks displayed inhibited behavior and was attacked by the
other puppies that were normally socialized. He was placed with other
dogs also raised in isolation; the dogs lived alongside each other,
without aggression but also without interaction (Fisher, 1955 in
Scott and Fuller, 1965). Dogs raised in isolation and placed in
contact with others of their species at 16 weeks are attacked and
rejected. When the experimenters mime play-fights
these same dogs, they are able to recover a positive dog-dog
interaction and complete integration in the same pack within a few
days (Fuller, 1961 in Scott and Fuller, 1965).
raised by cats until 16 weeks of age demonstrate preference for the
presence of cats, and submission - or fear - in the presence of dogs
(they also show no reaction to their reflection in a mirror). When
they are placed with other dogs at 16 weeks, they recover
intraspecies socialization in two weeks; they now prefer dogs to cats
and react to images of themselves in a mirror (Fox, 1971, in Pieters 1984).
On the other hand,
puppies raised in a family from 4 weeks of age (becoming used to
dogs, cats and/or children), without renewed contact with the
laboratory dogs, show greater familiarity with people than with dogs.
An adult sheltie (who had lived with a cat and two children) showed
sexual attraction for the cat and attacked all dogs (male and female
alike); a beagle became "attached" to a vacuum cleaner bag;
a basenji (who lived with a female dog) became a delinquent stray who
attacked other dogs (Scott and Fuller, 1965).
shows that when a puppy is acquired at 6 weeks this is already a
handicap in developing its adult social and sexual preferences.
We should also
mention that the first signs of humping (pre-imitation of future
sexual behavior) appear as early as 3 to 4 weeks (Scott and Fuller, 1965).
This behavior is
provoked by pressing on the sternum or the stomach. It is possible
that this is a factor in sexual
but it has yet to be proven.
To my knowledge,
no statistical studies have been made on dogs raised in isolation,
covering a broad range of breeds (for ethical reasons?), which means
that crucial experimental data are lacking. Our knowledge is
partially extrapolated from ethology studies in birds. Among birds,
imprinting lasts throughout parental care and this period is
shortened when there is a danger of mixing species. Preference is
given to visual and auditory imprinting whose effects last almost a
whole lifetime. With mixed imprinting, there is a preference (innate
predisposition?) for one's own species over a neighboring species,
and for this species over a more distant one (such as humans).
species identification (filial, fraternal and sexual imprinting) is
acquired during a sensitive phase of development, and depends on
"play-fighting" among puppies (litter-mates). This begins
about the third (3±½) week and ends somewhere between 11
and 17 weeks (12±5), when the dogs loose their ability to play
with unfamiliar dogs and become "serious" in defending
their group. In the absence of siblings, a puppy establishes
identification through care-giving, care-searching and/or playful
interaction with its parents or other dogs. This interaction must
last until at least, if not beyond, the 6th week. The presence of
other species during this period does not hamper identification with
one's own species.
The end of this
phase varies depending on factors that are internal (breed, line of
descendants, individual) and external (behavior of the mother, other
dogs, quality of the surroundings). A stressful environment (feral
dog) will close this phase ahead of time (probably around 7 to 9 weeks).
This type of
learning presents several characteristics:
They are similar
to those found among birds.
absence of other dogs
(own species) between 3 and 12±5 weeks fosters identification
with another species that is closest (in general humans, but
occasionally cats, rabbits, etc.) or an appropriate substitute
(stuffed animal, vacuum cleaner bag, etc.). This identification is
persistent, occasionally for life. In adults this leads to:
and attempts to copulate with the identification species (despite
activation by pheromones of one's own species), no behavior of this
type or else awkward attempts with a sexual partner of the same species,
for the identification species,
or fight) of one's own species (including mirror images).
absence of other dogs
between 3 and 12±5 weeks leads to relative, total or no
handicaps depending on circumstances:
of the dog's species identity at 9 weeks when it plays with other puppies,
attachment to the
identification species and disinterest or aggression towards canines,
despite the (almost) normal capacity to reproduce,
effects of a mirror
placed in the surroundings of a puppy isolated from other puppies
have not been studied (to my knowledge). Since no interaction is
possible with a mirror image, this seems to be a poor substitute for
A puppy is not
programmed to interact socially with another species. Twelve thousand
years of domestication, however, has shown that this is possible. The
dog's particular nature - a puppy has to learn to identify its own
species - can serve to foster socialization with other species
(called domestication when it involves interaction with humans).
Let's look at a
few experimental cases:
Puppies raised in
a semi-open environment in (nearly) complete isolation from humans
reacted differently towards an active unfamiliar observer depending
on their age. Each puppy was taken from the surrounding in which it
was raised, placed in contact with humans for one week, and again
tested. Fear in the presence of a human that handled him decreased
from 3 to 5 weeks, was minimal at 5 weeks, then increased again
afterwards. "Recovery" (improvement or disappearance of
fear) after a week of interaction-socialization was more efficient at
3 weeks; it was roughly the same at 5, 7 and 9 weeks (Freedman, King,
Elliott, 1961, in Scott and Fuller, 1965).
A puppy - raised
in the same type of surroundings - was placed 10 minutes a day with a
passive observer, calmly sitting in the room and paying no attention
to the dog (Scott and Fuller, 1965):
At 12 weeks a
puppy is easily frightened. Confinement and hand feeding enable it to
accept contact with its laboratory handler(s) but not with strangers,
and it still prefers the presence of dogs to that of humans (Scott
and Fuller, 1965).
reaction has been found in all breeds tested. When put on the
defensive a cocker's bite is "softer" than that of other
breeds tested (basenji, terrier, beagle, sheltie).
Fuller (1961), puppies raised in isolation in a laboratory develop
adequate socialization to humans if they receive two 20-minute
periods of human contact per week. This short contact, however, is
not enough for basenji puppies; this variability is thus truly linked
to breed (genetics) (Scott and Fuller, 1965).
demonstrate an investigation-attraction behavior towards the unfamiliar
as soon as they are able to express this attraction (almost adult
motor capacity), in other words at 3±½
weeks. This attraction subsides in
an almost linear manner after
the fifth week until
at least 9 weeks. The
attraction recedes under the influence of fear
of the unknown
behavior which grows after 5 weeks;
the puppy "recovers" from its initial fearful reaction
instantaneously from 3 to 5 weeks (investigation behavior effect),
and then it remains wary for longer periods as it grows older. At
12 weeks socialization requires active manipulation (mimicking
play-fights), at 14 weeks socialization seems to be impossible.
In birds fear of
the unknown is delayed when they are raised in isolation; this
phenomenon thus appears to depend on experience rather than maturing
of the nervous system (McFarland, 1981) - one must first be able to
refer to something "known" before fearing the unknown.
An arbitrary limit
can thus be set for spontaneous socialization to another species,
during a first
± 2 weeks. Nothing,
however, enables us to affirm or deny that rapid habituation to
close stimuli cannot be achieved after 12 weeks.
socialization (attachment) does not have the same characteristics
as species identification:
It is easily
to avoid de-socialization;
it is not
(generalisable) to all individuals of the species
concerned, but remains relatively limited to the individual's
characteristics. It is thus infra-species: it is a "type"
socialization (human: man, woman, adolescent, child, baby, black,
white, with/without beard, hat, white apron, etc.). The capacity
varies from one species to another (dog and wolf, more than coyotes),
breed (watchdogs less than other dogs, according to Fox, 1978), the
family line and individual (no statistical studies available).
(number of interactions) is variable and depends on factors that are
internal (breed, individual) or external (mother's fearful behavior,
quality of the surroundings, etc.).
depends on the presence of humans between 3 and 12 ± 2 weeks in
the surroundings in which a puppy develops and this socialization
must be continued throughout the animal's life. The lack of human
contact between 3 and 12 ± 2 weeks fosters the development of
fear/wariness of humans (feral dog).
absence of human contact leads to relative handicaps, such as
fear/wariness/phobia towards a type of human (children, men,...).
presence of different types of humans between 3 and 12 ± 2 weeks
facilitates a puppy's generalized socialization to humans.
presence of other animals leads to interspecific
socialization and attachment, and it counters predatory behavior.
socialization counters predatory behavior towards the type of
Emotional Self-Regulation (Homeostasis) Phase
is the ability of an organism to maintain an equilibrium in a
variable environment. Just as we have thermo-regulation (thermal
homeostasis), we can also speak of emotional and relational
homeostasis (Vincent, 1986). And we could even stretch the analogy
somewhat: the organism has a thermostat for heat regulation, and a
'ponderostat' to maintain an ideal weight (Vincent, 1986). Likewise
for emotional and relational homeostasis we could also envisage the
existence of a "sensoriostat",
respectively measuring a being's sensorial perception, and emotional
and social equilibrium.
Living in a group
and adapting to varied environments calls for a certain degree of
emotional equilibrium (with minor fluctuations). This adaptation is
possible only through habituation (disappearance of reactions) to
certain stimuli. That this process is essentially learned, rather
than genetically acquired is a sign of the species' ability to
conquer - and adapt to - varied and new environments. This ability is
an opportunity, but also a cause for risk.
Among animals, innate
exist, although in dogs they remain to be demonstrated: for example
the fear of "beating" or "gunshots" is not
innate, despite various writings along these lines. Nonetheless, you
can talk about acoustic sensitivity in individuals or breeds. This
has been demonstrated in rodents: certain strains of mice (DBJ/2J)
have shown an innate hypersensitivity to certain sound frequencies
which give them convulsions (Dantzer, 1988).
A large number of
fears arise from an individual's development. Is there a sensitive
phase during which it would be easier to establish emotional
homeostasis, enabling the individual to develop frames of reference (referential,
and long-term habituation? The answer is "yes".
Here are a few examples:
A dog's typical
reaction to an unfamiliar situation is fear: starting, fleeing or
inhibition. In a semi-open milieu, the dog tends to flee (and is
impossible to catch after the age of 4 months) (Scott and Fuller, 1965).
w w When it is
raised in isolation in a closed environment (0.2 m² cage) the
flight reaction does not develop; instead only inhibition or fear-provoked
aggression develop (Fisher, 1955; Fuller, Clark, Walker, 1960 in
Scott and Fuller, 1965).
If guide dogs for
the blind are placed in a foster family at 12 weeks, they generally
adapt well, but placement at 14 weeks can prove to hinder performance
in later training (Scott and Fuller, 1965).
experimented with puppies placed in contact with increasingly complex
at 5, 8, 12 and 16 weeks: as they grow the puppies tended to seek
out complex environments. Puppies raised in surroundings poor in
stimuli ("stimulus-poor puppies") and placed for the first
time in a highly stimulating environment at 12 or 16 weeks are
inhibited (fear) and search less complex environments. Enriched
puppies are systematically dominant in the presence of stimulus-poor dogs.
Male dogs are
raised in normally lightened cages for the 10 first months of their
life, but without any contact with the outside world (restricted
They are tested at 10 months old. Their activity level is 6 times
higher than average dogs raised in normal surroundings (motor
They learn slowly and forget easily (every trial is like a new
experience). When they have learned some behavior, they reproduce it
even when the rewarding factor has been removed (lack
of the extinction process).
Put in the presence of a bitch in oestrus, they show a state of
increased excitement but they direct it towards stereotyped habitual
behaviors and not towards the stimuli coming from the bitch. (Caston:
1993). For Caston, sensorial and social deprivation has impeached the
maturation of the brain: it can not exert an inhibitory influence on
the mesencephalic reticular formation (MRF) anymore; MRF is becoming
hyperactive, and produces unfocalised and unadaptative behaviors.
This has been verified by EEG recordings (in rabbits). In rhesus
monkeys, this deprivation
to high level of blood cortisol. *
primates show a greater degree of attachment to their mother
(pathological hyper-attachment), which led Bobbitt (1968, in Fox
1975) to propose that detachment
from the mother is a continual process linked to a young being's
attachment to the environment.
This conclusion can most likely also be applied to dogs.
practice we have observed dogs acquired at 3 or 4 months that had
phobic behavior, whereas their siblings, acquired at 2 months, were
participated in a study on the effects of a serotoninergic
psychotropic drug on the behavior of beagles raised in a kennel. The
beagles were chosen for their anxious-inhibited (depressive)
behavior. In exactly identical conditions, with limited human contact
(kennel staff) it was easy to choose 16 dogs of 8 - 13 months in
which the following symptomatic behavior towards the presence of
humans could be observed:
1986) (locomotor inhibition, almost crouching, tail between the
legs, head extended towards the stimulus presented),
single-breed kennel (little variation in genotype) in a relatively
deprived sensorial environment, there was a high degree of phenotype
variation with, nevertheless, a large percentage (more than 50%) of
dogs displaying inhibited behavior (more than 75% of the dogs were
anxious). An overall inhibition index was established (4 tests each
rated from 1 to 6, for a total ranging from 4 to 24 points, with 24
being the value for a normal dog).
"industrial" kennel conditions suffice to cause anxiety and
inhibition (undoubtedly favored in this case by the breed and
enclosure in a 9m² cage). Nevertheless a mere daily contact, and
handling every other week were enough to lower the level of
inhibition and anxiety in this group of young adult dogs significantly.
process of organizing stimuli from the outside world,
classifying them as known or unknown, agreeable, disagreeable or
indifferent (their "significance", meaning, socialization)
is similar to the process of interspecific
Eventually, this is merely one element in the acquisition of
self-regulation as regards particular stimuli because they are interactive.
We thus have a
phase of facilitated spontaneous learning that begins with a dog's
sensorial opening and investigation of stimuli (3
weeks) and ends when it develops fear of the unknown (12
± 2 weeks).
of this learning phase are the same as those of interspecific
socialization (facilitated but requiring reinforcement, low level of
The result is frames
acquired for each isolated or grouped sense (multi-sensorial referential,
(according to Fox, 1975), or even "thymostat"),
since each referential is probably a "mental object"
identified by an activated assembly of neurons, according to
determines the stimulation level at which the individual must begin
to adjust by activating the appropriate emotion (fear, wariness,
etc.) and adopting the most appropriate adaptive behavior
(investigation, avoidance, flight, aggression, inhibition, etc.).
that come into play are level of noise, visual agitation, intensity
of olfactory stimulation, number of vibrations, occupation of
three-dimensional space, flexibility or rigidity of movements, etc.
Here we can directly see the overall differences between a city and
rural environment of development.
The corollary to
the development of a puppy's attachment to its surroundings is its detachment
malleability enables it to rapidly adapt to almost all human
environments without undo stress.
Differences in the
quality and amount of stimuli a puppy receives in its environment of
development as compared to its adult surroundings determine the
degree of risk
it may not be able to adapt
its sensorial referential (thymostat) and thus achieve emotional
homeostasis (this includes development of phobias
Clinical observation has also confirmed that it is easier to
transfer from an environment with a high level of stimulation (city)
to an environment with a low level (rural) than the contrary. A puppy
raised in a deprived environment may be tempted to compensate for
this lack of sensorial stimulation by self-stimulation:
this is how certain stereotyped behavior develops, as well as
self-centered behavior (Fox, 1975), such as self-induced dermatoses.
stimulus-poor puppies run the risk of developing hyper-attachments
to their biological or adoptive parents (transposition of hyper-attachment
to its new human masters), which is a source of intolerance to
isolation, attention-seeking behavior, reutilization of behavior
acquired during illnesses, etc.
Precocious Learning-Conditioning Phase
This is another
variant of the phase sensitive to emotional development that occurs
between 3 ± ½ and 12 ± 2 weeks. Three behavioral
situations are of particular interest in precocious learning: elimination,
Elimination is a
reflex present at birth (it is provoked when the mother licks the
puppy's perineum) and becomes spontaneous around 2-3
weeks. From 3 weeks on, the elimination reflex disappears and the
puppy tends to leave its bedding to eliminate. At 8½
weeks it defecates in specific spots, usually at a distance from its
eating and sleeping area.
behavior (1) is preceded by sniffing around, probably in search of
typical odors (urine, feces, chlorine, ammonia, etc.) that will spark
the elimination reflex, (2) occurs almost every waking hour, (3) is
not activated for several hours during sleep.
It is thus the dog
breeder who conditions the location and medium favored for
elimination. The acquirer (when he receives the 7-9 week old puppy)
must then respect these socio-ecological conditions - he must limit
the space available when the puppy is not under human control and
provide the adequate elimination medium (why not a large litter box
in an apartment?) placed at the right location (at least 2-3 meters
from where the puppy eats and sleeps).
observation shows that when some puppies are limited to one spot and
medium until the age of 15 weeks (puppies kept in the house and
elimination on newspapers, for example) it becomes almost impossible
for them to learn to use other media and locations (conditioning) and
they retain themselves for hours when walking outside until they can
eliminate on their preferred medium and spot.
This ease of
conditioning can be put to an advantage in teaching dogs to eliminate
in gutters and other sewer outlets.
studies have been conducted on cats that became vegetarian or
imitated their mother who ate bananas. This type of conditioning is
also well-known in humans: preferences or aversions for certain odors
or tastes are already determined before birth (preference-aversion
experiments with a rubber teat dipped in garlic sauce) (Cyrulnik,
1989). We can postulate an intra-uterine
and post-natal food acculturation.
To my knowledge, no experiments have been made to determine the
duration of the food imprinting phase. It is possible that this phase
is similar to the self-regulation phase, both in its duration and
characteristics, since it engenders a food or feeding preference that
is persistent but changeable over time.
Feeding a puppy
solely on standardized food, invariable in taste and appearance (dry
or moist) can lead to long-term preferences and rejection of other
types of food (this has been clinically proven in cats). This problem
can be avoided by giving the puppy a variety of food.
distress when left alone in an unknown place increases from 3 to 6-8
weeks (maximum) then decreases until 12 weeks. The rising curve
reflects a progressive
attachment to a familiar place
(attachment location) while the descending curve after 7-8 weeks is a
sign of emotional
(more than habituation) and motivation to explore the unknown.
When a puppy is
acquired at 7 weeks and left alone at night it will bark in distress.
This barking disappears spontaneously after a few days as it becomes
familiar with its new home (with reassuring significance), unless its
behavior receives positive reinforcement from its new masters (who
come to pet, calm or scold the distressed puppy, or take it into
their room, all signs of attention - thus positive reinforcement).
The intensity and
frequency of this vocalization normally diminish, to be replaced by
intraspecific communication such as postures and rituals.
Vocalization is used to ward off strangers ('territorial' defense)
from the age of 11-15 weeks (see below). Some breeds have a greater
tendency to bark than others (Hounds, Poodles, Yorkshires, etc.).
Barking is easy to condition.
communication with humans, also a vocal and verbal animal, reinforces
the vocal element (learning by imitation), which then becomes
preponderant, even disruptive.
and learning to control biting
which begins at 3 weeks, can sometimes be painful when a puppy begins
cutting teeth, especially when its ears are bitten. A bitten puppy
whimpers or squeals. In a one-on-one or one-on-two fight the bitten
puppy is able to turn the tide of the 'battle' and bite its
adversary(ies). And this is precisely one of the "rules of the
game": to change roles, with the biter becoming the bitten and
w The puppy learns
to make an empathetic link between the opponent's squeal and the pain invoked.
biting negatively reinforces its intensity.
is thus stopped,
inhibited and controlled.
also lead to a certain hierarchization of relations (less than 25%
among litter-mates at 5 weeks of age)
The intensity of
the bite is (congenitally) variable depending on the individual, line
and breed, and can be modified considerably by training.
From 7 weeks on
puppies of a litter occasionally form groups to gang up on a lone
puppy. In these cases biting is uncontrolled and the attacked puppy
can be wounded (sometimes fatally). This phenomenon is more prominent
in certain breeds or lines (Fox terriers, according to Scott and
Fuller, 1965; Schnauzers, Huskies, and Malamutes among others, in my experience).
weeks play-fighting recedes; it becomes less aggressive and more
controlled. The fights become ritualized, a sign that stable
hierarchical relations are being established. Agonistic co-operation
is directed towards outsiders who are investigated and attacked in a
manner more "serious" than play-fighting.
control the intensity of its bite is actually part of a puppy's
growing general control
of its movements,
enabling it to adopt postures and facial mimics which become the
prevalent form of communication in animals having highly developed brains.
If the puppy's
to reproduce play-fighting postures and allow it to bite their hands,
arms and legs, this can lead to:
hierarchical dominance that can induce relational problems later on
(competitive aggressivity, sociopathy).
failure to control
the intensity of biting and risk of serious (wounding) biting in
Human skin is more
fragile than a dogs. Dogs that are family pets must be given more
thorough training in controlling the intensity of their bite.
A dog encouraged
at objects it holds in its jaws reinforces the biting reaction, which
is undesirable in a family pet (although it may be useful for police
and guard dogs).
failure to develop a dog's general motor control encourages hyperkinetic
forms of behavior.
and (Food) Hierarchization
A mother's care
and attachment towards her puppies are strongest during the first 3
weeks of life, and after that progressively recede.
The first phase of
weaning begins around 5 ± ½ weeks; the mother growls and
bares her teeth when puppies attempt to nurse (painful when the
puppies cut their teeth); the puppy yaps and rolls over on its back
and then learns to keep away from its mother's teats (Scott and
Fuller, 1965). An aggression-inhibition relationship - a
dominant-submissive hierarchization - is then established between the
mother and puppy for access to the mother's teats.
This attitude is
extended towards other mother-young conflicts and adopted in the
presence of other adults, as shown by the following personal
observation. In a husky breeding station the presence of the mother
beyond the 5th week led to her puppies' spontaneous submission to the
adults of the pack. In another station the mother was taken from the
breeding kennel when her puppies were 5 weeks old; these puppies were
not submissive to adults when they were first placed with the rest of
the group at 12 to 16 weeks. They did not use the submissive posture
(rolling over); the ritual was not acquired.
The presence of
the mother is thus favorable, even necessary, for the development of
appeasement-submission rituals and for the puppy's hierarchization in
the adult pack.
around 7 to 10 weeks.
From the age of 5
weeks the puppies begin to growl to gain possession of their food. At
the mother's arrival the puppies assemble in the attempt to nurse and
wait for their mother to regurgitate pre-digested food: they wag
their tails, lick and bite at the mother's chops and try to take
regurgitated food directly from her mouth.
The mother does
not compete with her young (7 weeks of age) and allows them full
access to the food (even if it is a bone) (Scott and Fuller, 1965).
This free access ends as the puppy becomes autonomous and takes its
place in the adult hierarchy (Pageat). At about 16 weeks the puppies
must take their place in line for food, i.e. after the dominant and
sub-dominant members, almost last. The puppies share and fight over
what is left, and gobble it up rapidly, to the complete indifference
of the dominant members who return to other activities. Puppies
attempting to snitch food while the dominant members are eating are
snapped at, growled at and threatened with being bitten. Some puppies
nonetheless manage through appeasement rituals to grab some food and
escape with it to a corner. Hierarchization for food privileges thus
occurs around 16 weeks.
When a pair of
puppies not competing for maternal attention are given a bone
there is aggressive competition ending with a winner and a looser.
The fight is rarely traumatic since adult fighting capacities are as
yet undeveloped. Hierarchization
varies with age and breed (Scott and Fuller, 1965):
25% at 5 weeks,
50% at 11 weeks,
75% at 15 weeks in terriers,
75% at 1 year in
basenjis and shelties,
50% maximum in
cockers and beagles.
varies by race and age. According to Scott and Fuller (1965), it is
predominant in short-haired fox terriers and basenjis (the male
dominates the female); and rare in shelties at 11 and even 15 weeks
(less than 50% of couples although this figure increases to 75%
around 1 year). This breed has been shown to "respect"
(accept) the female's priority to food. Food hierarchization is
average in cockers and beagles with no predominance of either sex.
The sheltie, on the other hand, develops a strong hierarchy in
defending the nest (spatial-territorial) and submissive members
(females) are pushed inside the nest.
"aggressive" the litter (line, breed), the greater the
tendency for linear hierarchization.
All puppies that
are correctly socialized will "leap" towards humans who
enter their area (bed, cage,...). The boldest ones are generally the
most dominant; they push back their submissive pack-mates, barring
access. Choosing a bold puppy (to avoid adopting a seemingly
unsociable one who stays at the back of the cage) may thus mean
selecting a dog that will be more aggressive to other dogs.
In conclusion: this
period leads to food hierarchization among litter-mates from 5 to 15 weeks
(occasionally later), between
puppies and adults from 4 ± ½ months, and reutilization of
(dorsal-lateral decubitus) towards
adults (from 5 weeks) and appeasement postures (nibbling
the chop and extending the paw) from
There can be
several risks involved in acquiring a puppy as a pet:
The human desire
is opposed to the normal (agonistic) parental behavior to wean the
puppy, detach oneself and encourage autonomy. The result can be
attachment, even hyper-attachment,
later engendering a separation anxiety syndrome.
The human tends to
fear for the puppy's health and thus pays particular attention
to its appetite,
watching it while it eats, indulging it when it begs, worrying about
finicky appetites or loss of appetite, varying food, and
hand-feeding, which become invested with the social symbol of dominance.
tendency of a human-dog relationship to develop into that of
parent-child, or parent-baby postpones the puppy's training towards
adulthood at 5-10 months as well as the order-obedience relationship
that is part of hierarchization. This delay
can foster sociopathy and certainly does not facilitate obedience.
lack of rituals
lead to their malfunction,
and even changes in their significance: if a dog in a submissive
posture is petted (positive reinforcement) it will adopt this posture
more often in the search for attention. The master then obeys by
petting it. The relationship risks reverting to one with a
demanding-dominant dog and a obedient-submissive owner.
Dogs have a cynomorphic
approach to the human-dog relationship, seeing it first as one
between puppy-adult dog, then as an interaction between pack-mates
(pre-adult-adult). A dog views human behavior through the social lens
of its own species and attempts to gain privileges as high as
possible on the hierarchical scale.
These risks are
avoided when dog owners behave in a way that can be assimilated to
the parent-dog relationship. It is clear how the Western world's
custom of acquiring pets favors the emergence of hyper-attachment and
sociopathies (dog as a toy, an object (a live teddy bear), a
substitute for children, a catalyser for social reactions, spoiled
Cognitive Sensitisation-Rationalisation Phase in Pre-Puberty
practice we have observed cases where phobic behavior (both towards
the dog's immediate surroundings and towards humans with which the
dog has little contact) and anxiety develop in pre-puberty. This
occasionally leads to an anxiety syndrome which I call
"anticipated defense behavior" (Dehasse, 1990a). A Bernese
sheep-dog (raised in Belgium) developed intermittent anxiety (with
pathological anticipations) around the age of 6 months, despite a
social and sensorial enrichment between 3 weeks and 4 months. Her
sister acquired the same tendency in a completely different
environment (Netherlands), as did her brother (in Switzerland). A
family of briards (Brie sheep-dogs) displayed the same tendency,
despite differences in the surroundings in which they were raised.
This enables us to propose two
the hypothesis of inherited
that of the
phase of pre-puberty sensitization.
study confirms there is a phylogenetic and/or epigenetic tendency for
pre-puberty sensitization. Fox (1978) studied primary and secondary
socialization in wild dogs and other canines that were raised in
identical environments and had daily contact with the trainer and
intermittent contact with unfamiliar humans. The wild canines all
remained attached to the trainer, at least until they reached
maturity, and then became less tolerant to contact with or proximity
to the trainer all the while welcoming him with appeasement postures
(whereas in the beginning he was welcomed with active postures:
jumping, licking, nudging).
Wariness of strangers develops:
quickly in the
solitary species (from 4 months in foxes),
later in species
of average sociability (around 1 year for jackals and coyotes),
and much later in
social species such as wolves (between 6 and 18 months) or dogs
(beagle, pointer or Chihuahua - between 1 and 2 years).
There is a
correlation in canines between wariness and the arrival of puberty
(10 months in the coyote, 2 years in the wolf), except in foxes
(wariness largely precedes puberty) and dogs (wariness follows
puberty which appears around 6 months). In dogs, precocious neutering
can delay or preclude the emergence of wariness towards strangers
(Brunner, 1968, in Fox, 1978), which could possibly confirm the
tendency's hormonal cause. It is Fox's opinion that domestication led
to a dissociation between gonadal maturing (precocity) and maturing
of the central nervous system (late).
Figures given for
dogs, however, are hardly conclusive. We all know how the age of
puberty, temperament, emotivity, sociability etc. can vary among
breeds and individuals. It is thus normal to see the appearance of
wariness towards strangers (or the unknown) or a loss of certain
social experience and sensorial references between 4 months (as in
foxes) and 2 years (as in wolves). This can also be compared to the
development of so-called territorial
Woolpy (1968, in
Fox, 1975) accustomed adult wild wolves to contact with humans in 6
months' time; he then isolated them somewhat from humans: in this
case they retained their socialization experience. He also accustomed
wolf cubs to humans, then isolated them: in this case there was de-socialization
(instability of precocious socialization). Young
animals need continuous reinforcement.
The same holds for
dogs: when a normally socialized puppy is isolated from humans and
placed in a kennel from 3-4 months of age to 6-8 months he becomes
fearful in the presence of humans, even the trainer. Woolpy's
interpretation (for wolves) is that socialization is limited by fear
of the unknown. Although the behavioral signs are precocious, the subjective
evolves gradually over a year (at least). Thus before socialization
can be acquired, the subjective (cognitive) element of fear must
In other words,
fear of the unknown has both an emotional and behavioral phase
(starting around 5 weeks) and a cognitive
It is my hypothesis
that an optimal period of attraction-habituation (acquiring sensorial
and emotion homeostasic referentials) closes with an emotional and
behavioral phase of aversion-fear of the unknown (5-14 weeks). There
follows a vulnerable
sensitization at pre-puberty or puberty
during which minor trauma can occasionally entrench wariness or fear,
(ill)adaptations, and cognitive and emotional distortions that
are undesirable in a dog living among humans in a city environment.
the often indissociable generalization) is the process that engenders
wariness, fear, phobia and anxiety. The cognitive process it entails
leads to a dog's anticipating
harmful situations that exist only in its mind (in a way, fear of
being attacked) and thus behavioral strategies (defense mechanisms:
flight, aggression, inhibition).
It is at this
sensitive age that dogs often begin group training courses. It is
imperative for the training environment to be controlled to ensure
the dog does not suffer any psychological trauma. At pre-puberty,
however, dogs emit pheromones that activate demonstrations of
authority by the group's dominant dogs. It is best to begin group
courses around 3 months of age, so that the dogs can become familiar
with each other and hierarchies before puberty.
Dogs are social
animals that need company, living in a hierarchical pack (or
family-pack). In clinical practice we continually observe cases of
conflicts (competitive aggression) at puberty, and later in
adulthood. These conflicts revolve around access to the opposite sex
(intra- or interspecific), but they can also arise over occupation of
certain areas of the group's common space (in the house in cases of
conflicts with the dog's owners, and rarely outdoors), in particular
feeding and sleeping areas.
Our hypothesis is
the following: an optimal period of intraspecific socialization
(identification) is followed by several crucial
that occur in successive phases: food, territory, socio-sexual at puberty
demonstrated the existence of a triple surge of social aggressivity
in dogs (male spaniels):
the first peaks
around 4-5 months with the dog returning to normal around 6-6½
months, when it begins obedience lessons (the owners assert their dominance);
- the second
surge coincides with the production of sexual steroids (±5 months);
- the third
corresponds to a "second attempt to obtain reproduction
rights" and only occurs in dogs who are allowed to live in the
house. Pageat explains this as follows: in a dog-pack, adolescent
males at puberty are pushed to the fringe of the group (by the alpha
male and the other older males). The third aggressivity surge does
not appear at this time. This is because in a group, the dominant
members react and put the young dog in its place each time it tries
to compete aggressively, barring its access (satellisation) to
socially invested areas and sexual partners. If the dominant members
fail to react, aggressivity is reinforced and the young dog rises in hierarchy.
experiment (1975) with various wild and domesticated canines, there
was a surge in aggressivity in male jackals and wolves at the onset
of puberty which increased until it peaked at 2 years. Aggressivity
was directed toward males (canines and humans). Note that canines are
perfectly capable of distinguishing the sex of humans, even when they
are dressed alike; this is probably through their sense of smell. Fox
also pointed out that competitive aggressivity may not appear in
wolves (males as well as females) until 4-5 years of age (maturity).
We have seen that
hierarchization occurs during a first
between puppies (from 5 weeks and is practically established,
depending on the breed, between 3 to 12 months), then between adults
and puppies (around 4 ± ½ months). This phase corresponds
to the first surge of social aggressivity identified by Pageat.
of hierarchization, puberty,
The young dog develops an interest for the opposite sex and for
areas occupied by the dominant members, who react by pushing the
adolescent to the fringe of the group. The process is complex: sexual
pheromones are awakened at puberty, activating "desire"
(Vincent, 1986), the dog exhibits courting behavior and is rejected
outright by the dominant member of the same sex, the only one of the
group with the right to exhibit his/her sexuality openly. The
adolescent is pushed from areas occupied by the dominant members
(high-placed positions, controlling passages, preferential sleeping
areas, etc.). It no longer has the right to greetings, licking and
other social attentions given by the other dogs. This is why this
phase is social, spatial and sexual.
This phase is
generally accompanied by territorial defense behavior. In some breeds
it occurs earlier, appearing from 2 months. In females, progesterone
favors territorial defense behavior, just as it favors whelping and pseudocyesis.
phase of hierarchization
occurs at maturity
(adulthood), an age that varies in dogs depending on the breed (from 8
months to 3
It reproduces the same characteristics as the second phase, only
this time with all the weapons, strength and passions of a mature adult.
If adolescent dogs
do not undergo hierarchization-satellisation, they gain hierarchy -
access to the privileges of the dominant member. The dog's relation
with its master thus becomes ambivalent, with conflicting
demands (dominance) - tolerance (submission). The lack of
comprehensible appeasement rituals favors attitudes of competitive
aggression (sociopathy) or substituting behavior (sometimes self-directed).
studies have been made on intra-breed variability, and inter-breed
studies have only concerned a few family lines in selected breeds. It
is thus impossible to form conclusions based on breed in view of the
number of dog breeds identified up to now (more than 200).
studies we have cited have never been conducted on a large number of
animals. The results mentioned are thus qualitative and speculative,
as are the dates and periods.
dog's ethogenesis evolves in (at least) three overlapping phases,
each related to a particular system: the neuro-vegetative
(neuro-glandular) - 1 to 7 weeks, the emotional
(limbic) system - 3 ± ½ to 12 ± 5 weeks, and the cognitive
system (cortex) - 5 ± 1 to 18 ± 10 months).
different phases of development
from -4 (before
birth) to +7 weeks
to 12±5 weeks
and sexual imprinting
to 12±2 weeks
Socialization - Thymostasis
- Conditioning, etc.
Rationalization - Territorialisation
presents a series of risks that can undermine the dog-dog and
dog-human relationship. A dog's epigenesis engenders multiple
temperaments that can be partially foreseen by controlling its
environmental stimuli. One factor favorable to emotional and
relational well-balance of a dog that must live with humans in a city
context is enrichment in the breeding environment.
It is the breeder's
to ensure temperamental selection and to enrich the development
environment (under veterinary guidance).
The role of the veterinarian
is essential because he/she sees the animal from 6 to 16 weeks for
its vaccinations. He/she thus theoretically has several occasions to
assess the puppies' early emotional and behavioral development and
can recommend preventive measures and training techniques.
can also play a role in educating potential dog owners to adapt their
relational needs to the dog's ecological and social reality, rather
than their own personal wishes.
must not only inculcate the bases for instrumental learning, he/she
must also take advantage of having a group of dogs to continue their
socialization and avoid de-socialization, both towards other dogs and
must find adequate counseling to prevent multiple relational
(systemic) and behavioral dysfunctions in their dogs. But they must
first be aware of the problem and know where to go for advice. It is
up to the veterinarian
Bateson B. Ontogénie,
in McFarland D., 654-674, 1981 & 1990.
Caston Jean. Psycho-physiologie
(tome I), Ellipses, Paris, 1993
Changeux J.-P. L'homme neuronal,
Paris: Fayard, 1983.
Collias N.E. (1956). The
analysis of socialization in sheep and goats, Ecology, 37: 228-38
(In Scott, Fuller, 1965).
Cyrulnik B. Mémoire de
singe et paroles d'homme, Paris: Hachette, 1983, Pluriel, 1984.
Cyrulnik B. Sous le signe du lien,
Paris: Hachette, 1989.
Cyrulnik B. La naissance du sens,
Paris: Hachette, 1991.
Dantzer R. Les Emotions,
Paris: Presses Universitaires de France, 1988.
Dehasse J., De Buyser Colette. L'Education
du Chien - de 0 à 6 mois, Montreal: Editions de l'Homme,
1983 & 1993.
Dehasse J., De Buyser Colette. A
quel âge doit/peut-on sortir un chiot, Veterinaria,
February 1989, n°193, p.26.
Dehasse J., De Buyser Colette. Mon
chien est d'une humeur de chien, Brussels: Editions Vander,
1989, 2d edition 1991.
Dehasse J. Le comportement de
défense anticipé pathologique et la paranoïa,
Prat. Méd. et Chir. de l'An. de Comp., 1990, vol.25, n°4,
Dehasse J. La socialization du
chiot et la privation de socialization, Conference GEPREC (Groupe
d'Etude pour les Problèmes de Reproduction et d'Elevage
Canin), Néonatalogie Canine, 28 October 1990,
Dehasse J. Epigenèse
sensorielle, émotionnelle et relationnelle du chiot.
Cahiers d'Ethologie, 12 (4) 443-66, 1993
Dehasse J. The semiology of
communication patterns between dog and man. BVCE 1 (1) 13-19, 1993.
Fox M.W. Canine Behavior,
Springfield, Ill.: Charles C. Thomas Publ., 1965
Fox M.W.. Integrative
development of the brain and behavior in the dog, Chicago:
University of Chicago Press, 1971.
Fox M.W. Socialization patterns
in wild and domesticated canids (ch.8), Stages and periods in
development: environmental influences and domestication (ch.9),
in The dog; Its Domestication and Behavior, New York &
London: Garland STPM Press, 1978, p. 141-152, 153-176.
Freedman D., King J.A., Elliot O. Critical
period in the social development of dogs, Science, 1961, 133:
1016-7 (in Fox, 1965).
Heath Sarah. Teaching a young puppy social
behavior (Part 1). Veterinary Times, April 1992: 12-13. Part 2.
June 1992: 6-8.
McFarland D. (ed). The Oxford
Companion to Animal Behavior, Oxford University Press, 1981,
1985, 1987. (Fr. Trans: Dictionnaire du comportement animal,
Paris: Robert Laffont, 1990).
Markwell P.J., Thorne C.J. Early
behavioral development of dogs, The Journal of Small Animal
Practice, 1987, vol.58, 984-991.
Nott Helen M.R. Behavioral
development of the dog, in Thorne ed.: The Waltham Book of Dog
and Cat Behavior, Oxford: Pergamon Press, 1992, ch.4, 65-78.
Pageat P. Etude Clinique et
Expérimentale du Comportement chez les Carnivores Domestiques,
Diss., Lyon, 1984.
Pageat P. (1986): Le syndrome de
Privation du Chiot, Le Point Vétérinaire, June-July
1986, vol.18, n°98.
Pieters A.. Socialization et
syndrome d'isolement chez le chien domestique, Cahiers
d'Ethologie Appliquée, 1983, 3 (1), 59-88.
Pieters A.. Socialization et
syndrome d'isolement chez le chien domestique, II. Les périodes
sensibles de développement, Cahiers d'Ethologie
Appliquée, 1984, 4 (1), 121-142.
Scott J.P., Fuller J.L. (1965): The
development of behavior (ch.4), The critical period (ch.
5), The development of social relationship (ch. 6), in Dog
Behavior: The Genetic Basis, Chicago: The University of Chicago
Press, 1965, Phoenix Edition 1974., 84-182.
Vastrade Françoise. L'examen
Comportemental du Chiot, Prat. Méd. et Chir. de l'An. de
Comp., 1986, 21, (4), pp. 273-284.
Vastrade Françoise. Le
syndrome de Privation chez les Carnivores: Genèse et symptômes,
Prat. Méd. et Chir. de l'An. de Comp., Jan.-Feb. 1987,
n°1, pp. 55-65.
Verdoux H., Bourgeois M. Modèles
animaux et Psychiatrie, Monographies de l'ANPP, vol.5, 18-59.
Vincent J-D. Biologie des passions,
Paris: Odile Jacob, 1986.
Voith V.L. Attachment of people
to companion animals, Symposium on the human-companion animals
bond, The Vet. Clinics of North America, vol.15, n°2, March,