30/06/2014 13:18 BST | Updated 30/08/2014 06:59 BST

#LikeAGirl - Why the New Always Ad Is Important

In the park the other day I overheard a parent tell their young daughter not to kick a ball 'like a girl'. This puzzled me for three reasons: the obvious being that she was, in fact, a seven year old girl; secondly that 'like a girl' was used as an insult (granted, sadly not surprising) - and lastly, the kick demonstrated a level of enthusiasm and skill I'd struggle to muster in a lifetime. I, for one, was impressed.

But since when did 'like a girl' become an insult - and why are we still using it?

I don't usually watch YouTube adverts. But the above question is exactly what Always explores in their important and thought-provoking new advertising campaign, and it is so important.

Girls are told that doing anything 'like a girl' is wrong. Boys are also told that doing anything 'like a girl' is wrong. As a result, boys are told to constantly 'man up' because acting like a girl is incessantly mocked. Both phrases impose strict gender boundaries without concern for individual identity - and they frankly don't do anyone any favours: girls learn that acting 'like a girl' is ridiculed, resulting in deep internalised misogyny, a lack of self-worth and confidence; boys learn that displaying any traits commonly associated with girls or femininity is ridiculed and so restrict their emotional expression, which can damage psychological health. The hugely important Miss Representation documentary, 'The Mask You Live In', discusses this damaging ideological masculinity, the consequences of feminising emotional expression and the harmful effects of the phrase 'man up' on young boys and men.

Boys and girls are told different things growing up, but the overriding message is clear: ideological masculinity is to be aimed for, and ideological femininity (AKA acting 'like a girl') is to be avoided at all costs.

Always' advert shows young women and men being asked to demonstrate what it is to 'run like a girl' or 'fight like a girl' - cue hyperbolic hand movement and hair touching. Young girls were asked to demonstrate the same things and the results were vastly different: they run as they know how to run and fight as they know how to fight.

Aged ten or thereabouts, they are free from the derogatory comments, discouraging remarks and painful humiliation which prevent girls pursuing their own interests and talents either as hobbies or careers. Indeed, a Bayer Corporation survey in 2010 revealed that forty percent of female scientists were, at some stage in their lives, discouraged from pursuing a career in science, technology, engineering or mathematics. Science or mathematics never being my academic strong points, in school I was naturally drawn to technology, computing and graphic design - and was repeatedly told by peers (and even one teacher) that my subject choices were 'boyish' and, by implication, unsuitable for me.

However, the differences in the performance levels of men and women are a result of socialisation rather than genetics. Lise Eliot told the Guardian that, "Yes, there are basic behavioural differences between the sexes, but we should note that these differences increase with age because our children's intellectual biases are being exaggerated and intensified by our gendered culture. Children don't inherit intellectual differences. They learn them. They are a result of what we expect a boy or a girl to be." The phrase 'like a girl' is constructed, then, by socio-cultural expectation. Girls are expected to throw badly or kick a ball badly - and these pre-existing expectations play a damaging role in the progression of female interest in sport, for example, or STEM careers. As a result, girls constantly compete against a pre-existing version of themselves, constructed by a gendered society which imposes rules on what they can and cannot do well. 'Like a girl' is used, simply, to assert male superiority - and its detrimental effects on both young girls and boys are clear.

The words 'like a girl' should not be synonymous with weakness or inferiority - it should, like Always' closing message, 'mean amazing things'. And at present, it doesn't mean amazing things. I was baffled by a recent article claiming the advert was disempowering and insulting when it so clearly addresses a prominent cultural issue. Until our vocabulary changes and we omit 'like a girl' and 'man up' as a means to promote female inferiority, Always' advert continues to be relevant. 'Yes, I kick like a girl and I swim like a girl and I walk like a girl and I wake up in the morning like a girl because I am a girl and that's not something I should be ashamed of', one girl states, and Always addresses this in a relevant and thought-provoking way.

Always' quest to boost girls' confidence during puberty is incredibly important in a society which criticises, undervalues and ridicules young women about everything from the natural state of their bodies to their career aspirations. The message is clear: feminising emotional expression and then ridiculing that same femininity is undeniably harmful. The phrases 'like a girl' and 'man up' are long overused: it's time to avoid their long-term psychological effects on developing young children and scrap them from our vocab.