Thus, there is a disconnect between the value of critical thinking and the degree to which it is supported by effective instruction (6). So, what does effective instruction look like, and how does it promote this HOT! (Higher-Order Thinking) skill? Helpfully, cognitive psychology provides us with some of the answers:

1. Context is King: The Importance of Background Knowledge

The important question at hand here is: Are some types of critical thinking more difficult to develop than others? The short answer is yes - subject-specific critical thinking appears to be easier to develop than general critical thinking. Studies have shown that critical thinking interventions improve subject-specific as opposed to general critical thinking (7), (8). This is also what we have found in our own research (9).

Possible reasons for why this is the case include the fact that the length of time needed to develop general critical thinking is much greater. This is coupled with the idea that general critical thinking is simply not as malleable as subject-specific critical thinking (10). For balance, though, some studies have reported improvements in general critical thinking indicating that under the right circumstances, general improvement is possible (6), (11). The key message here is that background knowledge is an important part of teaching critical thinking and the extent to which you aim to develop critical thinking beyond the scope of the course content should be assessed dependent on what is achievable in the given context.

2. Be Explicit: Approaches to Critical Thinking Instruction

The importance of background knowledge also has implications for critical thinking instruction (12). There are four main approaches to critical thinking instruction; general, infusion, immersion and mixed (13):

The general approach explicitly teaches critical thinking as a separate course outside of a specific subject. Content can be used to structure examples and activities but it is not related to subject-specific knowledge and tends to be about everyday events.

The infusion approach explicitly teaches both subject content and general critical thinking skills, where the critical thinking instruction is taught in the context of a specific subject.

Similarly, the immersion approach also teaches critical thinking within a specific subject, but it is taught implicitly as opposed to explicitly. This approach infers that critical thinking will be a consequence of interacting with and learning about the subject matter.

Lastly, the mixed approach is an amalgamation of the above three approaches where critical thinking is taught as a general subject alongside either the infusion or immersion approach in the context of a specific subject.