Brain scans to unlock mystery of shoppers' behaviour Because the participants need to be inside the 20-tonne machine, they will choose items from a list of products rather than browsing the shop on foot. Experts will analyse changes in blood flow brain activity as the participants go through the shopping process, to identify any changes in attention span, and their ability to ignore brands surrounding those on offer. Their theory, based on previous studies, is that after about 23 minutes of shopping customers will begin to tire and will start making decisions with the emotional part of their brain, which cannot accurately calculate value for money, rather than the cognitive part which governs logical decision-making. After 40 minutes, which is the typical length of time for a weekly shop, the brain should become so exhausted that it ceases to form rational thoughts altogether. Some studies have shown that a fifth of shoppers will buy items on special offer even if they are more expensive than the usual product, while nearly half ignore buy-one-get-one free labels and only take one item. Dr Paul Mullins, a psychologist at Bangor University, said: "We are really excited about this new research opportunity. Using advanced brain-imaging techniques we hope to get a better understanding of how shoppers respond to special offers. Phillip Adcock, managing director of SBXL, added: "We know from previous research that the brain behaves illogically when faced with the sort of information overload that shoppers are faced with in a typical supermarket. Now we have a reliable and scientific way of validating this research and understanding exactly what is happening in the brain during the weekly shop.