Cause and Effect: MDCAT Logical Reasoning notes

What these questions ask

You are given two statements (or a situation) and must decide how they are related. Standard options are:

1. Statement I is the cause and II is its effect.
2. Statement II is the cause and I is its effect.
3. Both are independent causes.
4. Both are effects of independent causes.
5. Both are effects of some common cause.

How to decide

• Time order: the cause must happen first. Words like "recently", "has been" or "will" help.
• Mechanism: there should be a sensible link. Ask "Could I explain how A leads to B?" Higher import duty raises cost, so car prices rise.
• Direction test: try both "A because B" and "B because A". Usually only one reads sensibly.
• No link: if neither can cause the other, check whether one event (a common cause) could produce both, or whether they are unrelated.

Cause	Effect	Link
Government raises petrol price	Transport fares increase	Higher fuel cost passed on
Large wheat imports	Domestic flour prices fall	Supply increases
Heavy monsoon rain	Rivers overflow	More water than channels can carry
Machine not maintained	Machine breaks down, causing injury	Wear goes unnoticed

Worked examples

1. I. The city's hospitals are overcrowded with dengue patients. II. Stagnant water has collected after weeks of rain. Answer: II is the cause, I the effect (standing water breeds mosquitoes that spread dengue).
2. I. The school announced a two-week holiday. II. Many families travelled to the northern areas. Answer: I is the cause, II the effect.
3. I. Tomato prices rose sharply. II. Onion prices rose sharply. If a flood destroyed crops, both are effects of a common cause; neither causes the other.
4. I. A student slept late. II. The city's bus drivers went on strike. Answer: independent causes (each may explain lateness, but they are unrelated).

Cause and effect in everyday science and safety

• At high altitude the air pressure is lower, so less oxygen enters the lungs with each breath; a climber may suffer altitude sickness (headache, breathlessness).
• In workplaces, accidents with equipment are commonly traced to poor maintenance; a badly planned layout is a design fault, whereas slippery floors or poor lighting are unsafe conditions.
• Continuous noise and interruptions reduce concentration and so reduce productivity.

Common MDCAT traps

• Reversing direction: the effect is often written first to confuse you.
• Correlation is not causation: two things happening together may share a common cause.
• An option saying the events are "unrelated" is wrong when an obvious mechanism links them.
• Choosing a result that is not stated or implied (e.g. "he felt more energetic" at high altitude).

Quick revision

• A cause comes first in time.
• There must be a plausible mechanism.
• Test both directions with "because".
• Two similar effects may share a common cause.
• Tax or duty increases usually raise prices.