The study, from researchers at the University of Waterloo in Canada, suggests that smartphone users who are intuitive thinkers - more prone to relying on gut feelings and instincts when making decisions - frequently use their device's search engine rather than their own brainpower.
Smartphones allow them to be even lazier than they would otherwise be, researchers said.
"They may look up information that they actually know or could easily learn, but are unwilling to make the effort to actually think about it," said Gordon Pennycook, co-lead author of the study, and a PhD candidate in the Department of Psychology at Waterloo.
"Decades of research has revealed that humans are eager to avoid expending effort when problem-solving and it seems likely that people will increasingly use their smartphones as an extended mind," said Nathaniel Barr, the other lead author of the paper, and a postdoctoral researcher at Waterloo.
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In three studies involving 660 participants, the researchers examined various measures including cognitive style ranging from intuitive to analytical, plus verbal and numeracy skills. Then they looked at the participants' smartphone habits.
"Our research provides support for an association between heavy smartphone use and lowered intelligence," said Pennycook.
"Whether smartphones actually decrease intelligence is still an open question that requires future research," he said.
The researchers said that avoiding using our own minds to problem-solve might have adverse consequences for ageing.
The study was published in the journal Computers in Human Behavior.