What is normal behaviour is not a given, but is consequent to the set of values and moral order society sets. Many of the things people see as abnormal in modern, western society have not necessarily been considered so in other times and places.
Indeed, the very word “normal” has changed enormously over time. Before the 1830s, normal was a mathematical term, referring to a particular type of angle. In the 1830s, it became increasingly used in statistics, with the “normal distribution” a new way of measuring populations. It was agreed that most characteristics would fit on a bell curve. For example, in terms of hand size: the largest number of people would have hands of a particular size, and the numbers of people with larger and smaller hands would steadily get lower.
It wasn’t until scientists began to apply this idea to health and illness that the term “normal” began to be seen as desirable. Average blood pressure, for example, was considered to be healthy, and those with high or low blood pressure would require treatment to try and bring them closer to the norm. Applying this idea to all sorts of social characteristics led people to see normal as being both good and healthy, rather than simply meaning the average of the population.
Establishing categorisations for ‘abnormal behaviour’ means to often draw on stereotypes and social expectations. This can be found in what scientists said about women in the turn of the 20th century.
“In past ages … simulation or deception of various kinds must often have been serviceable to the weaker female in protecting herself from the stronger (and sometimes cruel) male, as well as in enabling her sometimes to get her own way … therefore, at the present time the facility (instinct) for deception is probably greater in the average female than in the average male.” (Frederick Parkes Weber, 1911).