More threads by David Baxter PhD

David Baxter PhD

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By Emily Reynolds, British Psychological Society Research Digest
June 29, 2022

Those wanting to eat more healthily and save money are often advised not to go food shopping while hungry, the theory being that we make less prudent purchases when we’re more concerned with satisfying our immediate needs than thinking about long term goals. But how do other states of mind affect our purchases?

We’d probably not think anything of having a cup of coffee or a can of Coke before going shopping. But a new study, published in the Journal of Marketing, finds that caffeine may have a bigger impact than we think, with participants spending more and buying more things after a caffeinated drink.

In the first study, the team set up an espresso station over four days at a large chain store selling household goods in France. Each day, some shoppers were given espresso with caffeine while others were given decaf. Those who took the free coffee were asked to share the receipt for their purchases on leaving the shop, and answered questions on how excited, alert, and sleepy they felt while doing their shopping.

The results showed that those who had consumed caffeinated, rather than decaffeinated, espresso felt more excited and alert after drinking their coffee. They also bought a higher number of items and spent more overall. This was replicated in a second study, which took place in a city in Spain.

The third study, again in France, followed the same procedure, this time also tracking different product categories as well as cost. Again, drinking a caffeinated coffee before shopping led to greater spending and a greater number of purchases than drinking a non-caffeinated beverage. The types of items bought by caffeinated participants also differed — they were more likely than non-caffeinated participants to buy “high hedonic” items such as such as buttery or rich foods, which are considered more pleasurable than utilitarian things.

In a final study, students drank caffeinated or decaffeinated drinks before being asked whether they wanted to buy items from a “relaxation” category, which contained products of high hedonic value, or from a category containing more useful objects like notebooks and diaries. Participants bought less useful and more “exciting” items after drinking coffee, and again felt more excited and alert having drunk coffee — the potential mechanism for their buying and spending more. This is because we are more impulsive when we feel excited, and thus more likely to take a risk on products we might not go for when we are feeling calm.

This knowledge could obviously be of use to retailers — putting coffee stands or shops near the entrance of stores could make shoppers more likely to spend their money, and free coffee could potentially produce a significant return on investment. For this reason, the team argues that regulators should inform consumers of the impact of caffeine.

On an individual basis, the results are clearly useful too. If you are struggling with your spending at the supermarket, external factors like the cost of living crisis are probably more likely to be to blame than your own individual choices. However, being aware of the impact of caffeine could help people make small savings or at least be more aware of the potential for unplanned spending.
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