By Emma Young
We all know that using a smartphone interferes with our ability to focus on other things — like driving. But in 2017, a surprising result made international headlines: the mere presence of a switched off smartphone on the desk can impair working memory. Now a new study in Consciousness and Cognition, which has partially replicated and extended this investigation, has not found evidence to support the “brain drain” effect. However, the researchers, led by Matthias Hartmann at University of Bern, Switzerland, say that we shouldn’t start putting our phones back on our desks just yet.
The 2017 study was led by Adrian Ward at the University of Texas, Austin. His team found that people who’d been instructed to put their phones in another room performed significantly better on tests designed to measure their cognitive capacity than those who had their phones on the desk. They also did slightly better than participants who’d put their phone in a pocket or bag. It didn’t matter whether their phones were off or on or face up or down; just having the phone easily accessible meant that people had to resist the impulse to use it, which used some of their available cognitive capacity, the team concluded. This meant they had less to spare on the tasks, which drew on working memory.
Hartmann and his colleagues decided to investigate possible impacts on two other types of memory: short term memory and also prospective memory — remembering to do something in the future. They recruited 302 participants with a mean age of about 22, and asked all to put their phones into flight mode. Half were told that they could leave their phone on their desk, while the other half had their phones taken by the experimenter and placed on the opposite side of the room, so that, they were told, they would not be distracted by them. (Since it’s normal to ask study participants not to use their phones, the team didn’t expect this to alert them to the nature of the study.)
The participants were then presented with a series of pictures of easily identifiable objects paired with unrelated words. They were told to read each word aloud and to memorise the pictures. Every so often, they were asked to say out loud as many of the pictures as they could remember from the previous block, and an experimenter wrote these down. This was the test of their short-term memory. Before embarking on a second series of word-picture presentations, they were told to inform the experimenter whenever they saw a word that belonged in the category of “musical instruments”. This tested their prospective memory.
The team found that whether participants’ phones were in clear view or on the other side of the room made no overall difference to performance on these memory tasks. The participants had also completed questionnaires measuring their impulsiveness and their levels of smartphone dependence, and, when the team took a closer look at this data, a link — albeit an unexpected one — did pop out. Those people who ranked low for smartphone dependence did poorer on the prospective memory test when their phone was in view.
What should we make of all this? Given the 2017 findings, “the lack of an effect of smartphone presence on short-term memory performance was surprising,” the team writes. There were some methodological differences between the two studies, they note. Further work to more perfectly replicate the initial study is now needed.
As for the prospective memory findings, “our results seem to suggest that the benefit of smartphone absence disappears for people with higher levels of smartphone dependency,” the team writes, “as if the negative effects of missing one’s own smartphone when it is absent counteracts the positive effect of smartphone absence.” However, given the limited data so far, it’s too early to draw any firm conclusions.
The researchers stress that there is strong evidence from a range of earlier studies that “personally relevant” stimuli — like our phones — can impair our performance on cognitive tasks. “Our results should therefore not motivate people to put their smartphones on their desks at work,” they conclude.