“Sleep on it.” It’s time-worn advice for anyone trying to make a tricky decision. But does it work? Does it lead to better decisions, or at least ones that people feel better about? It’s an irresistible question for researchers who are already interested in the issue of how sleep affects emotion and memory — two important aspects of decision-making — and a new study in the Journal of Behavioral Decision Making sought to shed some light on it with laptop satchels. The results were very mixed, but they point the way to new experiments that will be able to tell us more.
The authors, led by Uma R. Karmarkar of Harvard Business School, conducted two experiments in which they brought in volunteers and showed them a bunch of different attributes about laptop satchel bags, each displayed alongside a photo of the bag — some of them positive, some of them negative. The participants were told that all of the information they were viewing was real and that they’d eventually be tasked with actually choosing which of the satchel’s they’d most want to own. After they did, they’d be entered into a drawing for a chance to win that satchel.
Each group viewed all of the attributes-photo pairs and rated their interest in owning the satchels twice, with a 12-hour interval between the session, though they didn’t have to actually choose until the end. To figure out the effects of sleep, the researchers set things up so that one of the groups had its first session in the morning and its second in the evening, while the other had its first session in the evening and its second the next morning.
In addition to asking the participants which of the laptops they wanted, the researchers also had them try to recall as many of the attributes as they could, since they wanted to figure out whether sleep impaired the recall of positive attributes, negative ones, or both. Then, after the participants made their final decisions, the researchers asked them how positively they felt about the quality of their decision and how likely they’d be to spend real money on the satchel. (The researchers also controlled for the fact that, for biological reasons, there might be inherent differences in how people make decisions in the morning versus at night.)
Summing up their findings, the authors write:
Our results demonstrate that a time period that includes normal nighttime sleep has distinct and complex effects on several elements of the decision process. Sleeping on a decision engendered more positive thoughts about the choice set. It might be assumed that this would make people feel better about their choice and more interested in pursuing it. However, counter to predictions based on previous literature, as well as common assumptions, sleep failed to improve perceptions of decision quality and indeed seemed to make participants more reluctant to consider commitment to the preferred item (e.g., spending money to purchase it). Given the novelty of these findings, it will be important for future research to investigate the effects of sleep on a broad range of decision types.
In other words, it was a mixed finding: The sleepers were biased toward remembering the satchels positively but weren’t more excited about their choice. It’s hard to know exactly what to take away from this, and, as the authors note, “future research” would be helpful.
Part of the reason it’s hard to interpret this is that the researchers didn’t follow up with the folks who actually received the bag — that is, for whom the “choice” they made led to a concrete reality. There are likely good reasons for this: You’d have to hand out a lot of satchels and run a longer, more expensive experiment to track this stuff in a statistically meaningful way.
But future experiments seeking to drill down into what’s really going on here with sleep and decision-making should try to base themselves on actual decisions. It would be interesting to see the results of a similar experiment (perhaps with a cheaper item) in which participants went home with whatever they chose and were asked about it a few days or a week later. In the meantime, this remains a very fuzzy subject. We can say with confidence that sleep has all sorts of cognitive benefits, but we can’t say with certainty that it benefits decision-making as compared to same-day choices — even if this study does offer some hints.