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Most people are familiar with the idea of a sensitive period for puppies that ends around 12 or 14 weeks. Is it possible that adolescence is also an important period for brain development and future behaviour?
Social experience plays an important role in shaping animal behaviour throughout development according to Sachser et al (2013). They consider the way the environment influences the mother and, in turn, the behaviour of her offspring (e.g. through stress hormones). This ensures the offspring is prepared for that environment as adults.
While the paper looks at the prenatal period right through to adolescence, it is the section on adolescent animals that is of most interest. They write that “the adolescent phase may provide a last chance for correction if the future environment deviates from that predicted in earlier phases.”
Most developmental research has focussed on pregnancy and the period shortly after birth. During this time, maternal hormones and behaviour have a large impact on the development of offspring. However, some parts of the brain are still plastic (i.e. able to change and develop) into adulthood. This includes the hippocampus and amygdala.
The scientists say, “There is increasing evidence that adolescence, that is, the gradual transition from childhood to adulthood, also represents an additional sensitive period (beyond the prenatal and early postnatal periods) in which behavioural profiles are routinely and profoundly shaped by social events.”
The potential for change during adolescence is necessary, they argue, because sometimes there will be a mismatch between the conditions in which the offspring is born and experiences very early life, and the environment in which it matures. In particular, they suggest future studies should examine the effects of this kind of mismatch, in order to find out more about this stage of development.
One example of the influence of the social environment in adolescence can be found in guinea pigs. If they spend their adolescence in colonies that include both males and females, they develop good social skills. As adults, they are able to get on with other guinea pigs in the colony without being aggressive; they are also able to become part of a new colony with unfamiliar guinea pigs. However, if they spend adolescence as part of a male-female pair, they become aggressive to unfamiliar males. Thus, the adolescent experiences have shaped adult behaviour.
The research considered by Sachser et al is mainly about mice, guinea pigs and wild cavies, but these ideas are thought to apply to the mammalian brain in general. They tie in with work on plasticity in the human brain. For example, Dr. Bruce Perry (2006) says that “important neurodevelopmental processes continue to take place throughout childhood and adolescence as the brain’s systems become more complex. Major cortical restructuring and myelination continue into early adult life.”
Writing about the implications for dogs, Riemer et al (2014) say, “… a major reorganisation of the central nervous system occurs during puberty, and there is growing evidence that adolescence can be considered as an additional sensitive period (beyond the prenatal and early postnatal periods), with profound effects on future behaviour (reviewed in Sachser et al 2013). There is evidence that steroid-dependent adolescent brain and behavioural development can be modified by social experience. Thus, experiences after the first sensitive period of socialisation, and in particular during adolescence, will also play an important role in determining the adult animal's behaviour.”
This is good news for poorly socialized adolescent dogs, as it means there is still an important window of opportunity in which to improve their behaviour. This is an age at which many dogs are surrendered to rescue organizations because they are no longer cute puppies and their increased size means their behaviour has become problematic. A better understanding of development during this stage would therefore benefit many dogs.
So does this research mean we don’t need to worry about puppy socialization anymore? Absolutely not! This is the most important time for ensuring your puppy will grow up to be a calm, friendly adult dog. (For suggestions, see this excellent article by Anne Springer on ‘five things you can do to bite proof your puppy’).
However, if you have an adolescent dog that hasn’t been socialized, it means it would be a good idea to build positive socialization experiences into their training plan.
Not enough is known about canine development, and more research is needed to confirm the biological and behavioural changes that take place during adolescence. We look forward to learning more about this important stage of development. The papers by Sachser et al (2013) and Riemer et al (2014) are open access and can be read at the links below.
What was your dog like as an adolescent?
Perry, Bruce D. and Szalavitz, Maia (2006) The boy who was raised as a dog and other stories from a child psychiatrist’s notebook. NY: Basic Books.Riemer, S., Müller, C., Virányi, Z., Huber, L., & Range, F. (2014). The Predictive Value of Early Behavioural Assessments in Pet Dogs – A Longitudinal Study from Neonates to Adults PLoS ONE, 9 (7) DOI: 10.1371/journal.pone.0101237
Sachser, N., Kaiser, S., & Hennessy, M. (2013). Behavioural profiles are shaped by social experience: when, how and why Philosophical Transactions of the Royal Society B: Biological Sciences, 368 (1618), 20120344-20120344 DOI: 10.1098/rstb.2012.0344