People who grocery shop Monday to Thursday can expect in-store music to swell their shopping bill by more than 10 per cent, according to new research from the University of Bath’s School of Management.

Weekday supermarket shoppers tend to be mentally tired from the working week and ‘pleasant’ music played in-store lifts their mood, making their decision-making on shopping items more intuitive.

With less scrutiny of purchases, people buy more products, treating themselves to additional items, or upgrading the quality of planned purchases.

By Friday, as people head into the weekend, they are already feeling less depleted and consequently music loses its power. People have more time, they feel more relaxed and in turn happier. The way they process information and make decisions on purchases changes, and music no longer impacts on shopping spend.

The traditional Monday to Friday work week is so ingrained in society that the effect is seen even for people on a different work pattern, or retired people.

“During the week people are short of time and many get their grocery shopping done after a full day at work,” said Dr Carl-Philip Ahlbom, from the University’s School of Management.

“Pleasant music appears to have a mentally soothing effect which impacts the way people shop. At the weekend people are essentially happier, and so the positive power of music is less noticeable. In fact, playing music at the weekend may even mean people buy less, possibly because it’s an additional stressor in an already busy environment.”

In the first study to look at the impact of music on sales on different days of the week, the researchers interviewed supermarket industry executives and shoppers to gather information about consumer shopping habits and how they differ throughout the week, combined with field experiments carried out in a Swedish supermarket chain in Stockholm. They tracked purchases from 7am to 11pm, analysing sales of approximately 150,000 shopping trips.

Playlists were developed by a professional sound design agency that specialise in music for public spaces. A background playlist featured music without vocals, described as elevator music, while a foreground playlist featured songs popular at the time of the study, with vocals. There was no distinction found between the two types of music.

“The research points to a clear uplift in sales, with high returns on the relatively modest investments required to install in-store sound systems (approximately £12,000 per store in the study),” said Professor Jens Nordfält, Co-director of the University’s Retail Lab.

“For retailers this could be an attractive investment to boost weekday marketing, but clearly they will need to look to other techniques to match the effect at the weekend, when consumers are feeling more energised and less susceptible to this particular strand of subconscious marketing.”

Understanding how music influences shopping on weekdays and weekends is published in the Journal of Marketing Research