Shoppers Explained a Jam Choice They Never Made
A supermarket experiment secretly swapped the flavour people had selected. Most manipulated trials went unnoticed, exposing a gap between choosing something and explaining why.
The Swap
You taste two jams, choose one and explain what makes it better. That seems like a straightforward report from your own senses. But what if the second spoonful is the jam you rejected?
In a 2010 Cognition experiment archived by Lund University, Lars Hall, Petter Johansson and colleagues tested that mismatch at a supermarket tasting venue. Shoppers compared jam tastes or tea smells, picked a favourite and were asked to sample their selection again while explaining the choice.
The researchers secretly switched the containers' contents. The outcome now contradicted the preference the shopper had just expressed.
What Slipped Through
According to the paper's abstract, no more than one-third of the manipulated trials were detected. Even markedly different alternatives did not make the switch universally obvious: detection was no higher than half of trials for contrasts including cinnamon-apple versus bitter grapefruit and mango versus Pernod scents.
That denominator matters. These are trials, not a claim that a fixed fraction of all people can never recognize a swap.
- Participants made a real initial selection.
- The researchers changed its apparent outcome.
- Participants then faced a request to explain that outcome.
The phenomenon is called choice blindness: missing a mismatch between what was intended and what was delivered.
The Hidden Construct
A preference and a story about that preference are not the same piece of evidence. This experiment places a trap between them. When the swap is missed, an explanation can be offered in a situation where the presented item is no longer the chosen one.
That does not prove people lack genuine preferences, that all explanations are invented, or that marketers can override anyone at will. It is a specific demonstration with two consumer goods and an engineered deception.
Why Revisit It?
The old experiment remains useful because it isolates a mistake that broader talk of manipulation often leaves vague. Before trusting an explanation, check that the outcome being explained still matches the original decision.
That is JitterSnap's practical inference, not a result tested across every kind of choice. Sometimes the revealing question is not why someone wanted the jam. It is whether anyone checked which jar came back.
The explanation sounded settled. The selection had quietly changed.