Table 1 Essentialism questionnaire adapted from Bastian & Haslam (2008). Reverse scored items are denoted by (R). Questions related to biological essentialism are denoted by an asterisk (*). Participants responded to each item with a 1–7 Likert scale

The boundaries that define the differences between addicts and non-addicts are clear-cut.

A person either has addictive tendencies, or they do not.

There are different types of people (i.e., addicts or non-addicts) and those types can be easily defined and are relatively clear-cut.

The kind of person someone is, is clearly defined, they either are an addict or they are not.

People fall into distinct personality ‘types’.

Generally speaking, once you know someone in one or two contexts, it is possible to predict how they will behave in most other contexts.

It is possible to know about many aspects of a person once you learn they are an addict.

When getting to know a person, it is possible to determine if they are an addict or not very quickly.

Knowing that someone is an addict can lead to accurate predictions of their future behaviour.

Everyone is either an addict or not.

Although addicts may have some basic identifiable traits, it is never easy to make accurate judgments about how they will behave in different situations (R).

With enough scientific knowledge, addiction can be traced back to genetic causes. *

Whether someone is an addict or not can be determined by their biological make-up. *

With enough scientific knowledge, the basic qualities of addicts can be traced back to, and explained by, their biological make-up. *

A person being an addict can largely be attributed to their genetic inheritance. *