How to answer the assumption questions in Watson Glaser Test Prep

One of the most difficult question types in the Watson-Glaser Critical Thinking Assessment is the assumption question. You are given an argument and then a statement of an assumption, and you are asked whether the assumption is made in the argument or not. In this post, I look at how to approach these questions, and why Watson-Glaser test prep for this section needs more than a large number of practice questions.

Using general knowledge to find assumptions

It is quite normal to use general knowledge to see whether an assumption is made or not. For example, someone says to you, "You are going to the North Pole. Please take some warm clothing." What is the assumption? The assumption is self-evident: it is going to be so cold at the North Pole that you will need warm clothing.

Or someone tells you, "Your parents are getting old, and you must now look after them." What is the assumption in this statement? The assumption is a value assumption: children should take care of their old parents.

Or someone says, "Work hard and you will succeed." What is the assumption? The assumption is that hard work leads to success.

These are very simple to process with general knowledge. But when you get into more complex arguments, you will not be very sure whether an assumption is made or not. The questions in the Watson-Glaser test are framed so that you cannot find the assumptions so easily.

What an assumption is in critical thinking

Everyone knows the general meaning of an assumption: it is something that is assumed and not stated. But in the context of critical thinking, you need a more exact understanding of what an assumption is.

In critical thinking, an assumption is an unstated premise that supports an argument. To see what this means, you need to understand the role of a premise in an argument.

In critical thinking, an argument is a conclusion supported by reasons. The term used for these reasons in critical thinking and in logical reasoning is premises. The premises and the conclusion, taken together, make up the argument.

Take a simple argument. A child goes to a teacher and says, "I could not come to school yesterday because I had a stomach ache." "I had a stomach ache" is the reason, or premise. "I could not come to school yesterday" is the conclusion. The two statements taken together are an argument.

In this argument, the child has stated the premise. So when you say that an assumption is an unstated premise, you are saying that the assumption is a reason that supports the conclusion. The person making the argument has simply not stated that reason.

What does it mean for a premise to support the conclusion? It means this: if the premise is true, the conclusion becomes more likely to be true. If it is true that the child had a stomach ache, it becomes more likely that the child could not come to school. So the premise supports the conclusion.

An assumption must do the same job as a stated premise: it must support the conclusion. This tells you two things. If a statement gives no support to the conclusion, it cannot be an assumption. But a statement that does support the conclusion is not always an assumption. A statement can support the conclusion even though the argument does not depend on it. An assumption is a reason the argument depends on, and to confirm that, you need the negation test.

The negation test: confirming whether an assumption is made

The negation test works like this. Ask yourself: if the statement is not true, does it weaken the conclusion? If it does weaken the conclusion, the argument depends on the statement, and the assumption is made. If it does not weaken the conclusion in any way, the assumption is not made.

Applying the test: the North Pole example

Go back to the first example: "You are going to the North Pole. Please take some warm clothing." The conclusion is that you should take warm clothing. The stated reason is that you are going to the North Pole. The proposed assumption is that it is going to be so cold at the North Pole that you will need warm clothing.

First, check support. If it is true that it is going to be so cold that you will need warm clothing, then the conclusion that you should take warm clothing becomes more likely to be true. The statement supports the conclusion, so it could be an assumption.

Now confirm with the negation test. Suppose the statement is not true, and it is not going to be cold enough at the North Pole for you to need warm clothing. Then the advice to take warm clothing has no reason behind it. The conclusion is weakened, so the assumption is made.

When support is not enough

Now go back to the third example: "Work hard and you will succeed." Suppose the proposed assumption is a stronger one: all those who work hard will succeed.

First, check support. If it is true that all those who work hard will succeed, then the conclusion becomes more likely to be true. The statement supports the conclusion, so it could be an assumption.

Now confirm with the negation test. The negation of "all those who work hard will succeed" is "not all those who work hard will succeed." Does this weaken the conclusion? No. Even if some people who work hard do not succeed, hard work can still lead to success, and the advice still holds. So the assumption is not made.

This example shows why support is not enough. The statement supports the conclusion, but the argument does not depend on it. The argument needs only the weaker claim that hard work leads to success. It does not need the word "all." The negation test is what shows this.

This is also why you need to negate a statement correctly. The negation of "all those who work hard will succeed" is not "no one who works hard will succeed." If you negate the statement that way, the conclusion collapses, and you get the wrong answer.

Watson-Glaser test prep: why knowledge of the theory is essential

For Watson-Glaser test prep, knowledge of the theory is essential. It is easier to answer the questions in this section if you understand the theory behind the test than if you rely on pattern recognition or on your native intelligence, of which everyone has plenty.

Knowledge of the theory helps you use that native intelligence to a much larger extent, and much more successfully, than if you were just to exercise it, or to look for patterns through extensive practice and use those patterns to answer the test.

The book

The theory behind the Watson-Glaser test is the focus of my book, Critical Thinking for Watson-Glaser. The book covers the theory first. It then discusses each section of the Watson-Glaser, and how the theory applies to each type of question.

The book also discusses causal reasoning. Causal reasoning is not tied to any one section of the test. However, many arguments link their reasons to their conclusion through a claim that one thing causes another. In some questions, whether the conclusion is true or not depends on understanding causation.

The book also gives you 168 practice questions with detailed answers. The answers show which concepts apply to each question.