Science is not always straightforward. Researchers may propose competing theories and deliberate over old data. This is true with research on how our brains make decisions. Many of the decisions we make have multiple layers of sub-decisions embedded within them. For example, should you play badminton with Jim tonight, or have coffee with Pauline now. A 2015 study showed that macaque monkeys (pictured) consider each sub-decision on its own, before drawing these together to make one over-arching choice. This creates a hierarchy where sub-decisions feed up and into to larger decisions. But when another group of researchers re-analysed the data, using new, more powerful software, they drew a different conclusion. They proposed that macaques consider all options at once, in a 'flat' process. In response, the first team re-ran their simulations. They say the results confirm their original theory of a hierarchy. But the debate about decision-making may continue.
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