A schema is a mental structure that allows problem solvers to recognize the particular category a problem lies within, and then use an effective strategy to solve that problem. Experts have multiple schemas, allowing them to quickly move towards a solution. Whereas novices do not, so they must use a means-ends analysis approach.
A means-ends analysis requires a large cognitive load because it works to eliminate possible answers (In the beginning, there is a near infinite field of possible answers). This is done by working backward from the goal, setting subgoals up along the way. In contrast, experts start moving towards a solution right away.
Experts and novices not only approach problems differently, they look at them in different ways as well. Studies have found that experts will categorize problems based on what strategies are used to solve them, while novices will categorize problems based on their surface structures. One finding from this type of study is that domain-specific knowledge is integral for critical thinking to be effective. You have to have the relevant background knowledge in order to correctly apply the appropriate skill to solve a problem.
You can’t think critically about what you do not know. This is a particularly controversial statement within the field of education. But it should not be. It is very commonsensical when you work to isolate the variables. For example, if a chemist was going to write an essay talking about how life works because of chemistry and you were going to write one as well, theirs would likely be much better. The reason being that they have a wealth of background knowledge to draw from. Whereas you, have Google. You can find the same information, but you will not understand it as deeply or be able to apply it as thoroughly because the knowledge has not been sitting in your head.
Another example of this can be seen when we look at foreign languages. How did the phrase “你吃了嗎?” originate and why is it used as a greeting? If you cannot read that sentence, you cannot think critically about it. It really is rather simple, background knowledge is necessary (critical even) for critical thinking. Think about it.