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.
Participants in the study who demonstrated stronger cognitive skills and a greater willingness to think in an analytical way spent less time using their smartphones' search-engine function.
"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."