When and why we forget to buy

You go to the supermarket knowing that you shouldn’t forget to buy toothpaste. You come home with bags full of groceries, but not with toothpaste. Does this sound familiar? It’s very common to forget to buy the items we intended to buy. Dr Daniel Fernandes and Prof. Stefano Puntoni of Rotterdam School of Management, Erasmus University (RSM) and two co-authors researched this phenomenon. For their research article, that was published in the Journal of Consumer Psychology, they have won the prestigious C.W. Park Award for Outstanding Contribution in March 2019.

Dr Fernandes and Prof. Puntoni, with former RSM professor and Dr Fernandes’s promoter Prof. Stijn M.J. van Osselaer (now Cornell University), and Prof. Elizabeth Cowley (University of Sydney Business School), researched consumers’ tendency to forget to buy items they intended to buy during grocery shopping. They expected a correlation between people’s search strategy and the frequency of item purchase on consumers' memory performance. 

Dr Fernandes: “People follow one of two search strategies. They either shop using a memory-based search by recalling their planned purchases from memory and directly search for the products. Or they use a stimulus-based search by systematically moving through a store, visually scanning the inventory and selecting the required items as they encounter them.”

Forgetting items

The researchers conducted an experiment in which 145 students were asked to buy 10 specific grocery items at an online grocery store. One third of the participants was told to use a memory-based search, one third to use a stimulus-based search and the other third was not told which search strategy to use. They replicated this experiment with 407 US workers who were recruited online. 

Dr Fernandes: “We found that people are more likely to forget the items they infrequently buy when using the memory-based search, but not when using the stimulus-based search. In fact, when using the stimulus-based search, people are sometimes even better able to remember the items they infrequently buy.” 

A separate memory test conducted with 83 participants confirmed these findings. Dr Fernandes: “People fail to take these factors into account when predicting their memory. As a result, they do not take appropriate actions to prevent forgetting such as using a shopping list.” 

Redesigning supermarkets

Forgotten grocery items means lost revenue for supermarkets. To increase sales, supermarket managers could try to help customers to remember all the items on their mental shopping list. 

Dr Fernandes: “Recent research shows that customers often don't walk all the way down the aisles in a grocery store. Not many people visit the middle of the aisle. So, when supermarkets place frequently bought items in the middle of the aisle and infrequently bought items at the ends, customers will actually see the items they infrequently buy when they walk to the items they frequently buy.”

Helping customers’ memory

Other strategies that motivate shoppers to walk the aisles of the store may also be effective at helping their memory for infrequently purchased items. For instance, placing a promotion in the middle of the aisle may motivate customers to move to the promoted item and be exposed to other products on the way. 

Managers may also help peoples’ memory by encouraging the use of shopping lists. Online grocery stores can allow customers to prepare a shopping list for later purchase. They can also help customers’ memory by stimulating them to use a memory-based search to buy frequently purchased items with a ‘shop by history’ function and a stimulus-based search to buy infrequently purchased items with a ‘shop by aisle’ function. 

Smart category structure

Dr Fernandes: “As it can be very time-consuming to let customers go through all the grocery items in a virtual aisle, it helps to have a smart category structure that allows customers to easily skip whole categories, such as the pets section, or parts of categories such as sodas or light beers. It also helps if certain categories are clustered, like breakfast cereals and milk and yoghurt.”

The article: Daniel Fernandes, Stefano Puntoni, Stijn M.J. van Osselaer, Elizabeth Cowley (2015) When and why we forget to buy, Journal of Consumer Psychology 26, 3 (2016) 363–380, is based on Daniel Fernandes’ dissertation from RSM. Dr Fernandes’ dissertation also won the Emerald/EFMD Doctoral Research Award 2015 for the best dissertation in the management category.

Rotterdam School of Management, Erasmus University (RSM) is one of Europe’s top 10 business schools. RSM provides ground-breaking research and education furthering excellence in all aspects of management and is based in the international port city of Rotterdam – a vital nexus of business, logistics and trade. RSM’s primary focus is on developing business leaders with international careers who can become a force for positive change by carrying their innovative mindset into a sustainable future. Our first-class range of bachelor, master, MBA, PhD and executive programmes encourage them to become critical, creative, caring and collaborative thinkers and doers. Study information and activities for future students, executives and alumni are also organised from the RSM office in Chengdu, China. www.rsm.nl

For more information about RSM or this release, please contact Ivo Martijn, media officer for RSM, on +31 10 408 2028 or by email at martijn@rsm.nl.

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