Drivers fidget with electronics and take both hands off the wheel more often as they develop trust in automated systems, according to new research.

A study from the Insurance Institute for Highway Safety (IIHS) and the Massachusetts Institute of Technology’s AgeLab looked at how automation affects driver disengagement.

Researchers studied the driving behavior of 20 Massachusetts-based volunteers over a month as they gained familiarity with advanced driver assistance features, examining how often they removed both hands from the steering wheel or took their attention away from the road to do things like use their cell phone or adjust the controls on the vehicle’s console.

One group of ten drove a Land Rover Range Rover Evoque equipped with adaptive cruise control (ACC), classed by Society of Automotive Engineers (SAE) as a Level 1 system.

Another ten drove a Volvo S90 with both ACC and pilot assist, a partially automated system that combines ACC with lane-centering technology, classed as Level 2. Level 2 is the highest level of automation available in production vehicles today.

The study found that drivers were more than twice as likely to show signs of disengagement after a month of using pilot assist compared with the beginning of the study.

“This study supports our call for more robust ways of ensuring the driver is looking at the road and ready to take the wheel when using Level 2 systems,” said IIHS Senior Research Scientist Ian Reagan, the lead author of the study. It shows some drivers may be getting lulled into a false sense of security over time.”