If you choose all six snacks for future occasions now, you may take six flavours. If you visit a counter once a week and choose only one, you may keep selecting the same favourite. This tendency to choose more variety simultaneously and less variety sequentially is called diversification bias. Classic experiments controlled the timing of choice and found that both purchase quantity and whether decisions were grouped into one occasion affected variety seeking.
Why might this happen? When an entire set is visible, the question “Does this collection look varied enough?” becomes salient. People may also anticipate boredom while being uncertain about what they will want on each future day, so variety becomes a hedge against prediction error. In a sequential choice, the immediate preference is clearer. If you genuinely want savoury crackers today, there is no need to take something sweet merely to make the week look balanced. The preference has not necessarily changed; the choice has been framed as either one portfolio or six present-tense decisions.
This does not make variety inherently bad. Dietary diversity can have real value, and buying ahead can save time. “Bias” means that the decision structure may push the collection away from what later sequential choices would have produced. Much of the original work used low-stakes goods such as snacks, and results can depend on the sample, time span and familiarity of the options. It does not show that every bulk decision is over-diversified. A practical response is to preserve sequential choice when later changes are easy. When everything must be selected in advance, ask whether each item serves a future need or merely makes today's set look attractively varied.
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