George H. Lawrence II, a Defense Department psychologist who studied such biological signals as brain waves, heartbeats and breathing as keys to improve performance and effectiveness, died Aug. 2 at Virginia Commonwealth University Hospital in Richmond. He was 80.

The cause was an aortic dissection, said his daughter, Holly Lawrence. Her father’s death followed a July 31 auto accident on Interstate 95 near Fredericksburg in which he lost control of the auto he was driving and went off the road, she said.

As a scientist at what is now the Defense Advanced Research Projects Agency (DARPA), Dr. Lawrence pioneered a practice of connecting people with computers in such a manner that the computer could monitor breathing, heartbeats and brain waves.

From information this produced, scientists could determine ways to cope more effectively with conditions that might impair performance of certain tasks, such as the use of weapons.

George Hart Lawrence II, a resident of Alexandria, was born in New York City. He graduated from Yale University in 1954, received master’s degree in experimental psychology and psychometrics from the University of North Carolina in 1957, and earned a doctorate in social and personality psychology from Boston University in 1962. He received a second doctorate, in clinical psychology, from Rutgers University in 1981.

Dr. Lawrence began his federal career in research psychology in 1965 at the Walter Reed Army Institute of Research, where his specialties included anti-terrorist and counterinsurgency projects. In 1968, he joined would become DARPA. Later in his career, he held visiting professorships in Sofia, Bulgaria, and conducted seminars in Bosnia-Herzegovina and Croatia.

From 1984 until 1996, he was principal scientist at the Army Research Institute in Alexandria.

On leaving federal service, Dr. Lawrence was a psychologist with Clinical Psychology Services in Fairfax. He also had a private practice in clinical psychology.

His avocations included deer hunting, horseback riding and hiking.

His first marriage, to Pamela Royall, ended in divorce. Survivors include his wife since 2000, Azra Japic Lawrence of Alexandria; two children from his first marriage, George H. Lawrence III of Durham, N.C., and Pamela Holabird “Holly” Lawrence of Northampton, Mass.; and four grandchildren.

— Bart Barnes