Dividing resources equally among all available options regardless of merit, simply because equal splitting feels fair.
Imagine you have a bag of marbles and four jars. Instead of thinking about which jar deserves the most marbles, you just put the same number in each jar because it 'feels fair.' Even if one jar is really important and the others don't matter, you still split them evenly because counting equal amounts is easier than actually deciding.
Naive allocation describes the systematic tendency for people to spread their resources—money, time, attention, or effort—equally across whatever options are presented to them, without considering the relative value or suitability of each option. This behavior is heavily influenced by the partition of options: if the menu of choices is restructured to include more items from one category, allocations shift toward that category even when underlying preferences haven't changed. The bias is especially pronounced when decisions must be made simultaneously rather than sequentially, as the simultaneous framing triggers a portfolio-like mindset where diversification itself becomes the decision heuristic. Crucially, this means that people's allocations can be manipulated simply by changing how options are grouped or how many sub-options exist within each category.
The same glitch looks different depending on the terrain. Finance, medicine, a relationship, a team — same mechanism, different costume.
Investors in defined contribution retirement plans tend to divide contributions equally across whatever funds are offered, causing their actual asset allocation to mirror the plan's menu structure rather than their own risk tolerance or financial goals. A plan heavy on equity funds produces equity-heavy participants, regardless of individual circumstances.
When clinicians or patients must allocate limited treatment time or resources across multiple health concerns simultaneously, they may default to equal attention for each issue rather than triaging based on severity, leading to undertreatment of the most critical condition.
First demonstrated by Itamar Simonson in 1990 in a marketing context (variety-seeking in consumer choices). Extended to financial decision-making by Shlomo Benartzi and Richard H. Thaler in 2001. The term 'diversification bias' was coined by Daniel Read and George Loewenstein in 1995.
In ancestral environments with high uncertainty about future needs and resource availability, spreading resources across multiple sources (food caches, foraging sites, social alliances) hedged against unpredictable losses. An equal-spread strategy minimized catastrophic risk when information about the relative quality of options was scarce or unreliable.
Recommendation systems and automated portfolio tools may inherit naive allocation when training data reflects users' equal-split behavior, perpetuating suboptimal diversification as if it were a revealed preference. Algorithmic resource-allocation systems may also default to equal distribution across categories when objective functions are underspecified, mirroring the human heuristic.
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