Do you talk on phone while shopping? This may be bad news for your wallet!

People who use their smartphones for making calls, texting or listening to music while shopping at a store are more likely to make unplanned purchases and forget items they had planned to buy, according to a study. Researchers from the Fairfield University in the US investigated the impact of mobile phone use on in-store shopping behaviour. They found that those who used mobile phones in store for purposes unrelated to shopping, such as making phone calls, texting, checking emails or listening to music, were more likely to make unplanned purchases and forget items they had planned to buy.

The study, published in the Journal of the Academy of Marketing Science, observed this effect even when phones were only used for part of the shopping trip, suggesting that in-store mobile phone use may consume attentional resources even after the phone is put away.

"Our finding that phone use that is unrelated to shopping negatively affects shopping behaviour was in stark contrast to beliefs held by consumers," said Michael Sciandra, corresponding author of the study.

"The vast majority of shoppers we asked thought that mobile phones did not have any negative effect," Sciandra said.

The researchers asked 231 participants to complete a simulated shopping task. While the participants either refrained from using their phone, or used it for an unrelated task either constantly (simulated phone call) or intermittently, they were shown a first person perspective video of someone grocery shopping.

The participants were given a shopping list of items and were asked to compare the list to the products the person in the video placed in the cart, or picked up and put down. The participants' mobile phone dependence was assessed via self-report.

The researchers found that consumers who are highly dependent upon mobile phones, characterised by excessive use of and reliance on the device, were the most at risk of deviating from a shopping plan while engaging in shopping-unrelated mobile phone use.

"Mobile phones are quickly becoming the principal distractor for many consumers and they offer a unique form of interruption," Sciandra said.

"Our findings may influence consumers' attitudes towards mobile phone use while shopping and persuade them to reflect on how these devices impact our lives, both positively and negatively," he said.