The school run was consistently running late. The family's response: buy three extra alarm clocks, one for each child's room. More noise, more certainty, more chance of everyone waking on time.

What they did not consider: turning off the television the night before and laying out clothes the previous evening, which would have cut preparation time without adding anything to the house at all.

Both solutions would probably have helped. But only one arrived naturally. The other required a different kind of question - not "what could we add?" but "what could we change or remove?"

This gap between what we reach for and what might actually work better is the additive bias.

What It Is

Additive bias is the tendency to favour additive changes - adding components, steps, or features - over subtractive changes - removing or simplifying them - when trying to solve problems or make improvements. Even when a subtractive approach would achieve the goal with fewer resources and greater efficiency, the additive option tends to be what comes to mind first.

Research has documented this pattern systematically. When participants were asked to improve objects, recipes, or schedules, they were significantly more likely to propose additive changes than subtractive ones, even in cases where removing something would clearly achieve the goal with less effort.

Why Subtraction Doesn't Come Naturally

Two factors combine to produce the bias.

The first is cognitive accessibility. Addition is the more mentally available operation when thinking about improvement. Adding something creates a tangible new element - a new tool, a new step, a new feature. The result of the change is visible. Subtraction, by contrast, creates an absence, which is harder to imagine and harder to present as an obvious improvement.

The second is the association between addition and progress. Adding something feels constructive. Removing something can feel like giving up, under-investing, or admitting that what was there was wrong. In organisational and social contexts, there are often subtle incentives to be seen as someone who contributes additions rather than subtractions.

Together, these tendencies mean that when people generate ideas for improvement, the additive set tends to be much larger than the subtractive set - not because addition is always better, but because it is the default direction of cognitive search.

The LEGO Tower Insight

A well-known experimental demonstration asked participants to make a LEGO tower more stable. The logical solution - well within reach - was to remove an unstable brick that was creating an imbalance. The overwhelmingly common response was to add bricks instead.

The instinct to add was so strong that even when removing a brick was the cleaner solution, most participants did not reach for it unless they were explicitly prompted to consider subtraction.

The same pattern appeared in recipes (participants added ingredients rather than removing ones that were creating imbalance), in schedules (participants added time blocks rather than removing commitments), and in essay editing (participants added text rather than deleting redundant sections).

Where the Bias Does Damage

Product and interface design. Features accumulate. Each individual addition seems justified. The accumulated weight of many small additions creates interfaces and products that are harder to use, more confusing, and less reliable than a simpler version would have been. The additive bias makes it systematically difficult to argue for removal.

Organisational processes. When processes fail or slow down, the response is usually to add a review step, a sign-off layer, or a reporting requirement. Removing an existing step - even one that is genuinely redundant - encounters resistance because removing it means something that was added is no longer needed.

Personal commitments. When life feels too full, the instinct is to add strategies for managing it: another productivity system, another calendar tool, another routine. The alternative - simply removing a commitment - arrives less readily and may feel more like failure.

Real-Life Contexts

See Additive Bias in everyday decisions

Pick a life context to see how this bias can show up outside the textbook.

Adding Funds Instead of Trimming Fees

An investor keeps adding new index funds to their portfolio, hoping to capture more market segments, while overlooking the option to drop a costly actively managed fund that duplicates exposure.

Illustrative scenario

Scenario

Maya, a mid-career professional, logs into her retirement account and notices the balance has grown slower than she expected. She decides to buy two more thematic ETFs that focus on emerging technology and renewable energy, believing the extra funds will boost returns. She does not consider selling the high-expense actively managed fund she already holds, which overlaps heavily with the new ETFs.

Where The Bias Enters

The default to add new investments feels like taking action and gaining coverage, while removing a fund feels like giving up potential upside, even though subtraction would lower costs and simplify tracking.

Decision Check

Before buying another fund she asks herself what could be removed to achieve the same goal with lower expense.

This scenario is illustrative. It explains the pattern and does not claim a documented public case.

Sources