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Omission bias

Omission bias is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Omission bias rather than just read about it. In short: Omission bias is the moral judgement in which people prefer omission (inaction) over commission (action), and tend to believe harm as a result of commission more negatively than harm as a result of omission. It works in three forms.

Key takeaways

  • Omission bias belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Omission bias to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Omission bias from memory before moving on to harder problems.

Reference excerpt

Omission bias is the moral judgement in which people prefer omission (inaction) over commission (action), and tend to believe harm as a result of commission more negatively than harm as a result of omission. It works in three forms. First, when omissions and commissions have the same bad outcomes, people find the former more favorable. Secondly, within the same choice set, the bad actions are regarded as morally worse than the factually worse inactions. Thirdly, subjects often find omissions more acceptable, compared to actions that bring an equally favorable result but with positive and negative tradeoffs. It can occur due to a number of processes, including psychological inertia, the perception of transaction costs, and the perception that commissions are more causal than omissions. In social political terms the Universal Declaration of Human Rights establishes how basic human rights are to be assessed in article 2, as "without distinction of any kind, such as race, colour, sex, language, religion, political or other opinion, national or social origin, property, birth or other status." criteria that are often subject to one or another form of omission bias. It is controversial as to whether omission bias is a cognitive bias or is often rational. The bias is often showcased through the trolley problem and has also been described as an explanation for the endowment effect and status quo bias.

Academic Evidence Baron and Ritov (1990) reported the omission bias in the scenario of vaccination. Although the outcome of disease is even worse, participants were reluctant to vaccinate if it showed a bad outcome (a potential death caused by side effect). Specifically, the minimum death rate of disease that encouraged participants to vaccinate was approximately ten times more than the death rate of vaccination. Spranca et al. further tested this phenomenon in scenarios including strategies for tennis tournament and trolley problem in 1991. Confronting the same negative outcomes, participants rated omissions as less bad than the corresponding commissions, while the deprecation of harmful actions was not accompanied with the same level of recommendation of the helpful ones. Overall, the negative part of active decisions is exaggerated, compared to that of omissions. Several studies have successfully replicated this finding. Recent replication also suggested the temporal-spatial generalization of omission bias. Children aged 7-8 and 11-12 reported similar moral judgement with adults: considering a behavior to obtain a self-directed benefit, participants from different ages showed a similar preference to the omission and often regarded commission as morally worse one. Except Western population, East-Asian sample also largely shared the pattern of omission bias, though nuances existed: Chinese participants reported a stronger tendency to deprecate a harmful action compared to American, probably because of Chinese traditional concept of Taoism which encourages ‘wuwei’ (inaction).

Mechanism Norm theory and reference point. Kahneman and Miller pointed that people tended to regard omissions as a norm, a neutral reference point, and actions as an abnormal activity. This distinction stemmed from people's easier imagination of behaviors they didn't adapt (or the omission situation) than what they carried out. For the abnormal, they demonstrated more sensitive feelings, targeting the benefits that should be there and thus resulting in the amplification of the loss and foregone benefits from commissions. Loss aversion. The comparison between omission and commission interacts with loss aversion, the principle that gains are weighed less heavily than losses of the same magnitude. Subjects perceived omissions as a normal situation. As a result, even if the outcomes of both actions and inactions are negative, the loss from omission can still be seen as a 'forgone gain', which is better than a pure loss; similarly, when the outcomes are all positive, the gain from omission turns to be a 'forgone loss', which is better than a pure gain. Therefore, inactions are always more acceptable than actions. Heuristic of asymmetric attribution. Heuristic is considered to be another reason of omission bias. A biased belief states that, compared to omissions, actions are considered to be tighter involved in the causes of outcomes because, also, they are more abnormal, and abnormal events are more likely to be seen as causes. From the perspective of actors, this can be translated into a blame that actors need to be responsible for the negative outcomes of commissions. However, the drawbacks caused by choosing to do nothing is not seen as actors' responsibility. This may root from an overgeneralization that the easy excuse of negative results caused by unintended omission (usually the absence of actors) also works to forgive the pitfalls of omission when no or a little evidence was left to prove whether actors have the choice to decide act or not to act. Therefore, when actors do not want to take charge of potential risks, omissions are largely favored. This explanation is believed to be irrational, because people fail to recognize the omissions that enact after decision-makers' consideration of the alternative as another kind of action (that is, act to do nothing), instead of the absence of actions.

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Omission bias

Start with the simplest possible case. Write down what Omission bias claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Omission bias before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Omission bias ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Omission bias

In research
Omission bias appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Omission bias in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Omission bias is common in secondary-school and first-year university syllabi. It links to neighbouring topics Barriers to critical thinking, Cognitive biases, Cognitive inertia, so understanding it makes those chapters shorter.
In everyday life
Look for Omission bias outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Omission bias in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Omission bias means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Omission bias out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Omission bias in simple terms?

Omission bias is the moral judgement in which people prefer omission (inaction) over commission (action), and tend to believe harm as a result of commission more negatively than harm as a result of omission. It works in three forms.

Why does Omission bias matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Omission bias?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Omission bias.

Tags

  • Barriers to critical thinking
  • Cognitive biases
  • Cognitive inertia
  • Deception
  • Error
  • Law of negligence
  • Moral psychology

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