Sources for further reading:
 Siegel and Bryson (2012). The whole-brain child. 12 proven strategies to nurture your child’s developing mind. London: Robinson.
 Shanker, Stuart (2016). Self-Reg: How to Help Your Child (And You) Break the Stress Cycle and Successfully Engage with Life. Canada: Viking
 Lieberman, M., Eisenberger, N., Crockett, M., Tom, S., Pfeifer, J., Way, B. (2007). ‘Putting Feelings into Words: Affect Labeling Disrupts Amygdala Activity in Response to Affective Stimuli.’ Psychological Science, 18(5), 421-428.
 Barrett, L.F., Lindquist, K., Gendron, M. (2007). ‘Language as context for the perception of emotion’. Trends in Cognitive Science, 11(8), 327-332.  Brooks, F. (2014) The link between pupil health and wellbeing and attainment. A briefing for head teachers, governors and staff in education settings. Public Health England.
why words matter to kids' social development
Believe it or not, kids actually have an innate desire to behave well and please their parents - it’s just certain impulses that sometimes get in the way!  Interestingly, a big contributor to social development in children in general is language.
The neuroscience behind controlling your impulses
The ability to moderate your actions and emotions is called self-regulation. Self-regulation means being able to calm down when you’re upset because you lost your toy, or because your sibling ate the last biscuit, and being able to adjust how you behave to fit each situation. The power of self-regulation is all in the brain chemistry.
Ever wondered why temper tantrums seem to come out of nowhere? Or why a kid can seem totally fine one minute and totally irrational the next? If you were to scan the brain of a child who is experiencing stress or anger, you’d see that the limbic system - the area of the brain associated with strong emotions and impulses - is lit up in red. When the limbic system is overactive in this way, decisions and actions are being driven by impulses, while the rational part of the brain is largely inactive.
But all is not lost! If the child manages to calm down then the pattern is reversed and the most active area of their brain becomes the prefrontal cortex - the area associated with rational thinking and learning - and the activity of the limbic system decreases. 
Why words matter for self-regulation and emotional intelligence
We’re Mrs Wordsmith so of course we care about why words matter! But if you don’t believe us, believe the scientists! Studies have shown that a particularly effective way to calm down intense feelings is to express them through language. Recent neuroimaging studies have shown that expressing emotions through language calms intense brain activity.
In an fMRI study, participants were asked to look at emotional images while researchers observed the activity in the area of the brain responsible for emotions (the amygdala). The researchers then compared the brain activity of participants who were asked to process the images silently, to the brain activity of participants who were asked to express how the images made them feel. The results showed that participants who didn’t express their emotions through language showed significantly more intense brain activity than participants who were asked to express how the image made them feel.  In other words, this study showed that expressing emotional experiences using language calms down our brain and regulates our explosive feelings!
Words help children learn self-regulation by naming and understanding their complex emotions. So if you’ve ever said ‘use your words’ when trying to get your child to articulate their feelings, your instincts are on spot on! Not only does expressing emotions with language have calming effects, but when children are able to identify and label their emotions with the right words they can start to make sense of them.
Research has shown that kids who are able to label emotions like “jealousy” or “frustration” have more positive social interactions and perform better in school than those with a more limited vocabulary.  This is because the more words we have to describe our feelings, the more precise our understanding of our own and others’ emotions can be.
Overall, a wealth of research has shown that social-emotional skills such as emotional intelligence and self-regulation are strongly related to school success and overall well-being.  And now we know that words can contribute to the development of these skills!
Sources for further reading: