Number of siblings can affect adult personality

Researchers assessed the behaviour of rats born with different numbers of siblings, a variable that has rarely been taken into account until now. The group contained rats from litters with less than ten pups, litters with ten to fifteen pups and litters with more than fifteen pups.

The mother's behaviour towards her pups was also studied to discover whether this influenced any emotional changes appearing in their adult life. The results of this experiment demonstrated that rats born from larger litters display less anxiety in adulthood, are more willing to explore new surroundings and react better to adverse or stressful situations when compared to the ones born and raised in smaller litters.

Previous studies revealed that rats receiving more maternal affection and attention present less anxiety when they are adults. In this sense, the present research demonstrates that in addition to the mother's care, relationships between siblings also have a significant impact on how rats behave later on in life.

According to the authors of the research, “The first years of life are very important for the development of our nervous system and for how we behave when we are adults”. Although the research was carried out with an animal model, “it is a very useful model in studying the effect early life experiences have on adult behaviour”.

The study, directed by Universitat Autònoma de Barcelona Institute of Neuroscience researchers Roser Nadal and Rosa Maria Escorihuela, was published in the journal Physiology & Behavior.