Women wearing hairpins take their selfie in Beijing, China, September 25, 2015. Wearing antenna styled hairpins in the shape of various flowers and plants at scenic spots has become a new trend in Beijing. [Photo/Agencies]

A weird but interesting trend has spread across China's social network sites: selfies of people with grass "growing" out of their heads. In fact, it's not rare to see people with hairpins with plastic grass on their heads on the streets. Some celebrities, too, have joined the trend.

It's interesting to see this ACG (animation, comic and game) fashion trend spreading to the real world. But psychologically speaking, it's an accidental phenomenon thanks to the social prevalence rule and common human mindset.

"Grass growing out of the head" is a typical way, in the ACG world, of portraying a cartoon character's dorky but adorable nature. Actually, such cartoon characters have a strand of hair sticking out of the head. The strand of hair has evolved into a tuft of grass, because of the similarity between hair and grass. The image of a cartoon character with a tuft of grass on the head spread from sub-culture circles to mainstream culture through a set of emoticons on Weixin, the Chinese version of Wechat. The cartoon character in the emoticons is a white globular creature with grass growing out of its head.

The popularity of grass hairpins is probably another successful commercial campaign, but it also highlights some basic psychological issues.

Enterprises have developed a set of mature marketing skills. The key to promoting a product is keeping its price low, and making it easy to promote and access.

The grass hairpin has almost no threshold in terms of purchase or use. It costs a few yuan (less than $1) and sellers don't emphasize on its copyright or brand. A person can buy the hairpin almost anywhere, making it easy to "grow" grass on the head. Besides, a selfie with a grass hairpin on the head posted on social media is perhaps the best promotion for the product and the "dorkable" image it represents.

The popularity of grass hairpins also reflect a common social psychology, that is, group psychology, which played the most important role in the rapid spread of pop culture.

Bandwagon effect refers to individuals who doubt, even change, their own views, judgments or behaviors because of the influence, guidance or pressure of other groups. And their direction of change is in accordance with the direction of the majority's choice. That is what we call "following the general trend".

The Asch conformity experiments are a typical example of the bandwagon effect. Psychologist Solomon Asch showed eight participants two cards with lines: the first with one line, the other with three lines labeled A, B and C. One of the three lines on the second card was the same as that on the first, with the other two most definitely longer or shorter. Seven of the participants, who were actually hired "actors", deliberately gave wrong answers several times to confuse the only real participant into changing his judgment, which he did almost every time he was influenced by the "actors" to do so.

The interpretation of group psychology is that, as a social being humans tend to seek recognition of the majority in a given group in order to win support and survive.

One of the most significant factors that could influence the degree of bandwagon effect is whether it is easy to be followed. Although "growing grass out of the head" is a silly idea, it can be easily copied and spread as a fashionable trend.

Such trends don't last long. But it's interesting to see people falling prey to such funny, and at times silly, trends again and again. Perhaps we are not as wise as we think. Some times we are only "the naked ape", a not-so-smart creature that Desmond Morris wrote about in his books, one of which was actually titled The Naked Ape.

The author is a PhD candidate in psychology in Britain and the co-founder of online psychology organization Yosumn.