Scientists at the U.S. Army Research Laboratory at Aberdeen Proving Grounds, Md., are studying ways to help soldiers hold and fire their weapons more steadily and accurately. The Association of the U.S. Army reported that the team is using an artificial trigger that measures a shooter’s trigger pull. Each subject also is wearing a “mini vibrator” on the wrist, a sensor wire, and an ultrasound device that charts muscle activity. Tests show that when activated, the vibrating device tends to help shooters handle their weapons more steadily.