Critical Thinking: The Watson Glaser Skill That Gates Law, Consulting, and Executive Hiring
Critical thinking is the hardest aptitude family to prepare for because the traps are subtle, not obvious. It is the section where candidates with strong academic records routinely underperform and where disciplined prep produces the largest score gains. Law firms, consulting firms, and the civil service fast stream test critical thinking specifically because it filters for the kind of careful argument analysis that on-the-job work demands. One week of the right drills can move you from the 40th to the 75th percentile.
What critical thinking actually measures
Critical thinking tests the ability to evaluate arguments in a disciplined way. Unlike logical reasoning, which tests formal rules, critical thinking tests how well you can apply judgment to real-world-like passages. You are given a short paragraph, then asked whether a conclusion follows, whether an assumption is being made, whether an inference is correct, or whether an argument is strong or weak.
The most famous critical thinking test is the Watson Glaser, used by most Magic Circle and Silver Circle law firms, by the top management consultancies, and by many civil service and government positions. The Watson Glaser has five sub-sections: Inference, Recognition of Assumptions, Deduction, Interpretation, and Evaluation of Arguments. Each sub-section tests a distinct skill with its own traps.
Critical thinking is different from general reasoning because the test requires you to ignore what you know and judge only what the passage supports. That restraint is harder than it sounds. Candidates with domain expertise in the passage topic often score lower than non-experts because they cannot help bringing outside knowledge to bear.
The five Watson Glaser sub-skills
Each sub-section of the Watson Glaser tests a distinct ability. Prepare each separately.
Inference
Given a statement of fact, rate a proposed inference on a scale from definitely true to definitely false. The trap is assuming the inference is true when the passage makes it merely probable. Each level of certainty must be treated distinctly.
Recognition of Assumptions
Given a statement and a proposed underlying assumption, decide whether the assumption is made. The trap is assuming the speaker made a reasonable-sounding assumption when they did not. You must find the assumption the statement actually requires.
Deduction
Given a premise set, decide whether a conclusion follows necessarily. This overlaps with logical reasoning but with more realistic phrasing. The trap is conclusions that are plausible but not deductively supported.
Interpretation
Given a passage, decide whether a conclusion follows beyond a reasonable doubt. Stricter than inference. The trap is "probably true" conclusions that are not certain enough.
Evaluation of Arguments
Given an argument, decide whether it is strong or weak. Strong arguments are both relevant and important. Weak arguments are either irrelevant, trivial, or based on a flawed premise. The trap is evaluating arguments based on whether you agree with the conclusion.
Worked examples
Three hand-crafted critical thinking questions with full walkthroughs. Do them with a timer first. Then read the solution.
The passage tells us City X has the highest walk-to-work proportion. It does not tell us how people in other cities commute.
Residents of other cities might drive, bike, take public transit, rideshare, or walk at rates close to but lower than 60 percent.
The inference specifically claims "most residents drive." That requires over 50 percent driving in other cities. The passage gives us no information on driving rates at all.
The trap is assuming drive-to-work is the default alternative to walking. It is not in many cities. Transit can easily be the top mode.
The correct answer is "Insufficient Data."
The statement proposes stopping the basketball program AS A RESPONSE to falling grades.
For that response to make sense, the speaker must be assuming the basketball program is at least a contributing cause of the falling grades.
If the speaker did not assume this, stopping the program would not address the problem.
This is a necessary assumption, not just a possible one. The statement cannot be rationally made without it.
Compare to a question like "Stopping the basketball program will make the students want to play football instead." That assumption is NOT required by the statement, because the statement is about grades, not about sport preferences.
A strong argument is both relevant and important.
The argument is relevant: it addresses a direct connection between voting rights and the taxpayer/policy-subject status of 16-year-olds.
The argument is important: the "no taxation without representation" principle is a foundational political argument in democratic theory, and education and employment policy does directly affect 16-year-olds.
Whether you personally agree with the conclusion is irrelevant to evaluating the argument.
The trap is evaluating based on whether 16 is "too young" (a different argument) or on whether the argument is sufficient (strong arguments need not be the only or complete argument). The evaluation is specifically about the given reasoning.
Answer: Strong.
Tests that use critical thinking
Critical thinking is most heavily weighted in professional services hiring: law, consulting, and accounting. If your target employer is a Magic Circle firm or a top-tier consultancy, critical thinking is likely the highest-stakes section.
The gold standard. Magic Circle and Silver Circle law firms, top consulting firms, and civil service fast stream all use it. Five sub-sections, 40 questions, 30 minutes.
A shorter variant used by corporate employers for senior hiring.
More common in academic settings, occasionally used by government employers.
Used mainly in academic and healthcare hiring.
Four critical thinking mistakes that sink Watson Glaser scores
Importing outside knowledge
Watson Glaser is brutal on candidates who answer from expertise. If the passage is about economics and you are an economist, set your knowledge aside. The test measures passage-based reasoning only. Domain expertise can lower your score.
Confusing likely with certain
On Inference questions, "Probably True" and "True" are distinct answers. On Interpretation questions, only "True" counts as following beyond a reasonable doubt. Candidates who collapse these categories lose points on every borderline question.
Over-identifying assumptions
A proposed assumption must be necessary for the statement to make sense. It cannot merely be consistent with or plausible alongside the statement. Most "Assumption Not Made" answers are traps that sound related but are not required.
Evaluating arguments by agreement
Strong and weak refer to argument quality, not conclusion quality. A weak argument for a true conclusion is still weak. A strong argument for a wrong conclusion is still strong. Separate the two dimensions rigorously.
A 14-day critical thinking plan for Watson Glaser
Days 1 to 2: Sub-skill diagnostic
Take one practice section in each of the 5 sub-skills. Note which you scored lowest on. That is your priority sub-skill.
Days 3 to 4: Inference drills
Drill 40 inference questions. Focus on the 5-level certainty scale: definitely true, probably true, insufficient, probably false, definitely false. Train yourself to never collapse the middle three into one.
Days 5 to 6: Assumptions drills
Drill 40 recognition-of-assumptions questions. Rewrite each proposed assumption as "The speaker could not make this claim without assuming X" before answering. This verbal reframe helps.
Days 7 to 8: Deduction and interpretation drills
Drill 30 questions in each sub-section. Deduction rewards formal logic. Interpretation rewards strictness about "beyond a reasonable doubt."
Days 9 to 10: Evaluation drills
Drill 40 evaluation-of-arguments questions. The key discipline is separating argument strength from conclusion likability.
Days 11 to 12: Timed mocks
Take two full 30-minute Watson Glaser mocks. Review every wrong answer and classify the error: was it sub-skill-specific, or was it a cross-sub-skill trap?
Days 13 to 14: Light review
Review your mistake journal. Do not take new mocks in the 48 hours before the test. Sleep 8 hours each night.
Related reading
Critical Thinking FAQs
Critical thinking rewards disciplined prep more than any other question type.
Full-length, timed critical thinking practice modeled on the Watson Glaser 5-section format.
Start Critical Thinking Practice