Paul J.A. Timmermans

The resident-intruder paradigm: a standardized test for aggression, violence and social stress.

This video publication explains in detail the experimental protocol of the resident-intruder paradigm in rats. This test is a standardized method to measure offensive aggression and defensive behavior in a semi natural setting. The most important behavioral elements performed by the resident and the intruder are demonstrated in the video and illustrated using artistic drawings. The use of the resident intruder paradigm for acute and chronic social stress experiments is explained as well. Finally, some brief tests and criteria are presented to distinguish aggression from its more violent and pathological forms.

Parturition behaviour in pluriparous Java-macaques (Macaca fascicularis)

This study presents a quantitative description of the parturition behaviour shown in captivity by five pluriparous feral Java-monkeys (Macaca fascicularis). Three distinct phases in the parturition process are demarcated: a phase just before the actual birth, in which bearing down contractions occur, called Prepartus; the birth itself, called Partus; and a phase immediately after birth, in which severing of the umbilical cord and expulsion of the placenta occur, called Postpartus. The first signs of imminent child-birth are hollow postures of the back, stretching of legs, walking to and fro and touching the vulva. Characteristic parturitional postures are squatting and sitting, hollow and arched backs. Other parturition behaviours are stretching, reaching for support, anogenital investigation, licking, manipulation and inspection of the own body and birth-products and consuming of the placenta. Periparturitional behaviour is mainly characterized by changes in frequency, intensity and orientation of behaviour, which also occur outside the context of delivery. The newborn baby has a grab-grib reflex and a clampreflex, which results in a strong ventro-ventral body contact with its mother.

Effects of rearing and exposure condition upon the acquisition of phobic behaviour in cynomolgus monkeys

Young monkeys were confronted with a harmless novel object in their familiar home-cage environment. The effects of two rearing conditions (mother and surrogate mother) and two confrontation conditions [presence and absence of the (surrogate) mother] upon the acquisition of phobic behaviour were studied. Most surrogate-reared monkeys showed persistent maladaptive avoidance behaviour with respect to the object during tests, from 7 months of age onwards. Most mother-reared monkeys approached the object during tests taking food near it, from 7 months onwards. The confrontation condition had no effect upon behaviour with respect to the object. As no aversive conditioning procedures have been applied, merely presenting a harmless object appears to be enough to set off persistent avoidance in surrogate-reared monkeys. Further investigation of the origin of the phobic behaviour is interesting in view of developing animal models of human phobias of which no conditioning history is known.

The Influence of Repeated Motherhood on Periparturitional Behavior in Cynomolgus Macaques (Macaca fascicularis)

We studied the influence of parity on periparturitional behavior by quantitatively comparing the behavior of 10 primiparous and 11 multiparous cynomolgus macaques. We found a considerable number of significant differences, some of them affirming the outcome of previous descriptive studies. During the prepartus phase, primiparae showed more locomotion and “action postures” and fewer “resting postures” than multiparae. Further, primiparae spent more time straining than multiparae and were straining in a greater variety of postures than multiparae, which were straining predominantly in a squatting posture. In the postpartus phase, primiparae needed more time than multiparae to get their young in ventroventral position. Primiparae licked mainly the newborn;multiparae licked mainly their own bodies. Finally, fewer primiparae than multiparae ate the placenta. The discussion extensively treats theories concerning parity effects. We explain behavioral differences between primiparae and multiparae in terms of novelty of the female’s internal state and novelty of the neonate and in terms of learning. We stress that the mechanism behind the so-called parity effect cannot be revealed without paying more attention, next to learning, to age, to experience with pregnancy, and to experience with parturition. Further, we argue that the immediate acceptance of the newborn at birth and the differences between primiparae and multiparae might play a crucial role in the search for the mechanism behind the onset of maternal behavior.

The effect of absence of the mother on the acquisition of phobic behaviour in cynomolgus monkeys (Macaca Fascicularis)

Abstract Monkeys reared in a peer group with surrogate mothers avoided a large unfamiliar object provided with food that was presented to them at the age of 1 yr. Peers reared by their parents and separated from them after 1 yr approached the same object and took food from it. This remarkable difference in behaviour appeared to persist for years, although no aversive experience whatsoever had been conditioned to the object. In adulthood the difference between the two groups was absolute; the mother-reared monkeys all approached the object, whereas the monkeys reared by surrogate mothers all avoided the object. This behavioural difference is described and tested systematically and an explanation of its origin is presented in terms of Bronsons (1968) theory concerning the phasic development of fear. The phenomenon under study shows a striking resemblance to human phobic behaviour and offers a new animal analogue for the study of the acquisition and therapy of human phobias.

The influence of rearing conditions on maternal behavior in cynomolgus macaques (Macaca fascicularis)

We studied the influence of rearing on the adequacy of maternal behavior by comparing 20 harem-reared and 15 peer-reared primiparous cynomolgus monkeys. We used them plus 11 wild-caught females to extend this comparison to multiparous subjects and also to compare primiparae with multiparae. We observed no behavioral effect of rearing and parity. Primiparous maternal adequacy amounted to 93% in peer-reared subjects and to 95% in harem-reared monkeys. We extensively discuss theories concerning rearing effects. Leitmotifs throughout the discussion are survival value of maternal behavior immediately after parturition and predictive value of this behavior for the further course of maternal behavior. Support is accumulated for the hypothesis that certain tactile and visual experiences suffice for the development of adequate maternal behavior.

Responses to novelty in phobic and non-phobic cynomolgus monkeys: The role of subject characteristics and object features

In two previous studies it has been shown that most surrogate-reared cynomolgus monkeys became phobic of a harmless object (a big paper bag) while most mother-reared monkeys approached that object. Results of the first study seemed to indicate that the phobic reaction was restricted to the bag. Barnett and Cowan (Interdisciplinary Science Review, 1, 43-62, 1976) and Suomi (Anxiety disorder in childhood, pp. 1-23, 1986), however, reported that subjects (respectively rats and monkeys) that avoided a first novel object also avoided subsequent novel objects. In the present study we exposed phobic (bag-avoiding) and non-phobic (bag-approaching) monkeys from the study by Röder, Timmermans and Vossen (Behaviour Research and Therapy, 27, 221-231, 1989) to several big and small novel objects. Our results show that, irrespective of their rearing conditions, subjects that were phobic also avoided big novel objects while subjects that were non-phobic approached big novel objects. The reaction to small novel objects was independent of the previous reaction to the bag.

The role of modeling in prevention and extinction of phobic behaviour in cynomolgus monkeys (Macaca fascicularis)

In previous studies surrogate reared cynomolgus monkeys have been shown to become phobic of an unprepared harmless object. In the present study an attempt was made to prevent the development of phobic behaviour in young monkeys and to extinguish avoidance behaviour in phobic monkeys. In the first experiment subjects were exposed to the object in company of their (surrogate) mothers which approached the object. In the second experiment phobic subjects were exposed to the object in company of non-phobic conspecifics which approached the object. The results of the first experiment show that modeling was unsuccessful in preventing the acquisition of phobia in the surrogate-reared monkeys but seemed successful in accelerating approach in the mother-reared subjects. The results of the second experiment show that during the modeling treatment the phobic subjects followed the model and approached the object. However, in post treatment tests all subjects but one relapsed into avoidance. The effect of modeling during treatment is interpreted in terms of coactive facilitation.

Effects of Mother's Rearing Condition and Multiple Motherhood On the Early Development of Mother-Infant Interactions in Java-Macaques (Macaca Fascicularis)

In this study we investigated the effects of a mothers social rearing condition and her parity on maternal behaviour, infant behaviour and behavioural development during the infants first ten days. With respect to parity two classes were involved: primiparae (PR), and pluriparae (PL) with at least a 5th infant. For the primiparae two rearing conditions were involved: having grown up within the family group (FPR) which included mother, other mothers, juveniles and babies, and having grown up in a peer group (PPR) with no other companions than animals of the same age. All pluriparae were group-reared. It appeared that maternal and infant behaviour and behavioural development were not influenced by the mothers own rearing condition, but they were affected by earlier experience with motherhood. All PPR mothers were adequate mothers and, in the first ten postpartum days, PPR and FPR mothers displayed nearly the same degree of restrictive infant-directed behaviour, which may be due to the novelty of having a baby. It is probably due to restriction that PR infants became not as active and explorative as PL infants in their first ten days. PL mothers were more permissive and rarely rejective. We found no support for the being-properly-mothered hypothesis, the observing-how-to-mother, and the learning-to-mother (by play) hypotheses, or the maternal rejection hypothesis. Mothers become less infant-directed and less restrictive and give the infant a wide action radius by habituating to and practising with their own infant. Within the limits of the cage and with only the mother present, it is primarily the infant that takes the initiative to make excursions.

Is maternal behavior correlated with later explorative behavior of young guinea pigs (Cavia aperea f. porcellus)

Abstract The results of previous studies, mostly involving primates, have shown a correlation between mothering styles and later explorative behavior of the young. On the basis of our previous study on the existence of mothering styles in guinea pigs we conclude that three main components of maternal behavior are useful for these kinds of studies: locomotion, affiliative behavior, and aggressive behavior. In the present study we examined the extent to which these components were correlated with later explorative behavior of guinea-pig pups. The later explorative behavior of 48 pups from 16 mothers was measured after weaning in a series of tests designed to highlight different aspects of exploration. The results indicate that maternal behavior does not have a predominant correlation with later explorative behavior of the pups. Correlations were not found between the affiliative and aggressive behavior of the mothers and the later explorative behavior of the pups. Mothers scoring high on locomotion had pups that showed more explorative behavior than did the pups of mothers scoring low on locomotion. This correlation, however, was not linear and was significant for only one parameter.