Level 4 — Upper Intermediate · Argument Writing
Task 29: Naming a Mechanism and an Alternative Explanation
Write a causal claim that explains how the cause produces the effect, then honestly name one alternative explanation you haven't ruled out — the writing side of Lesson 29's causal reasoning skills.
Learning Objectives
By the end of this task, you should be able to:
- Write a causal claim that names the mechanism connecting cause and effect, not just the bare sequence
- Distinguish a confounding variable from the cause being claimed, and name one honestly
- Use causal-strength language (contributed to, largely responsible for) instead of overclaiming sole causation
Introduction
Lesson 29 taught you to read a causal claim critically — checking for a mechanism, a confounding variable, and an alternative explanation the author might be quietly skipping. This task asks you to build that same honesty into your own writing: state your cause, explain how it works, and admit what else could be going on.
The Rule, for Writing
Core Concept
A strong written causal claim has three parts: the cause and effect themselves, the mechanism (how the cause actually produces the effect, often signalled with "by + V-ing" or "through"), and at least one alternative explanation or confounding variable you're willing to name rather than hide. Prefer "largely responsible for" or "contributed to" over an unqualified "caused," unless your evidence is genuinely that strong.
Example
Switching to LED lighting cut the warehouse's energy bill by a quarter. (bare causal claim) The reduction happened by replacing older bulbs that wasted most of their energy as heat. (mechanism) However, the warehouse also reduced its operating hours that same quarter, so shorter hours likely contributed to the savings as well. (confounding variable, named honestly)
Your Turn
Your Turn
Write a paragraph describing a real or plausible cause-and-effect situation you know something about (a change at work, in a routine, or in a system you use). Include, in order: the causal claim, a sentence naming the mechanism (how the cause produces the effect), and a final sentence naming one honest alternative explanation or confounding variable you cannot fully rule out. Use "largely responsible for" or "contributed to" rather than an unqualified "caused."
Vocabulary in Context
mechanismnountechnical
the actual process by which a cause produces its effect, not just the fact that it does (প্রক্রিয়া/কার্যপদ্ধতি)
Often with causal mechanism, underlying mechanism, mechanism by which
“The report describes the mechanism by which understaffing raises error rates.”
confounding variablenoun phrasetechnical
a third factor changing alongside the claimed cause that could explain the effect instead (সহ-পরিবর্তনশীল কারণ)
Often with control for a confounding variable, possible confounding variable, identify a confounding variable
“Seasonal demand is a confounding variable that could explain both changes.”
Model Answer
Show a model answer
Moving the port's container-booking system online was largely responsible for the drop in queueing time at the gate. This worked by letting trucking companies reserve arrival slots in advance, so fewer drivers showed up during the same crowded morning window. However, the terminal also added a second inspection lane that same month, so faster inspections likely contributed to the shorter queues as well, and the booking system alone cannot claim the full credit.
Self-Check
Self-Check
- Did you name the mechanism — how the cause actually produces the effect — not just assert that it does?
- Did you honestly name one confounding variable or alternative explanation, rather than hiding it?
- Did you use "largely responsible for" or "contributed to" instead of an unqualified "caused"?
- Did you write this directly in English, without translating from Bangla first?
Next: Writing 30 — Evidence, Claims, Data & Interpretation: writing a paragraph that keeps your data and your interpretation of it in two clearly separate sentences.