In the Lab With Stevens & Skinner

  • Stevens Skinner 1
  • Stevens Skinner 3
  • Stevens Skinner 2
  • Stevens Skinner 6
  • Stevens Skinner 4
  • Stevens Skinner 7

The basement of Memorial Hall was home to the Psychological Laboratories of two pioneers—S. S. Stevens and B. F. Skinner.  

Stanley Smith Stevens—known as “Smitty”—was the first to move in.  In 1940 he established the Psycho-Acoustic Laboratory (PAL) at the request of the US Army Air Corps.  His mission was to improve communication in noisy combat aircraft flying at high altitudes.  Working in tandem with Leo Beranek’s Electro-Acoustic Laboratory, Stevens employed a speech articulation test to measure how noise, low air pressure, and fatigue affected intelligibility.   His talkers and listeners were conscientious objectors.

The lab’s work resulted in better microphones and earphones in helmets and oxygen masks.  Those cushioned earphones loved by today’s audiophiles?  They were Stevens’s invention.  Can you hear me now?  Testers of acoustic equipment still use “Harvard Sentences” of phonetically-balanced phrases as standards.
After the war, Stevens studied scales of measurement.  He also developed his psychophysical power law, which related the strength of a physical signal to its perceived intensity.

Burrhus Frederic Skinner came to Harvard in 1948 at E. G. Boring’s invitation.  Like Stevens, he also had done war work.  In “Project Pigeon,” Skinner had trained pigeons to guide missiles to enemy targets.  After he came to Harvard, Skinner’s pigeon Lab sat at the opposite end of the basement from Stevens’s office.
Whereas Stevens believed that agency resided in each organism, Skinner did not.  He argued that behavior was shaped by the environment and the consequences of actions in a process he named “operant conditioning.”  Variations in behavior, like those in biology, were presumed to occur randomly.  Selection by consequences acted like natural selection to strengthen the most effective actions in individual behavior:  Of course, species that responded to consequences would also have greater survivability.
Selection by consequences was examined experimentally. In a typical experiment, a pigeon would be placed in a sound-proofed chamber.   A rack of instruments in another room controlled different schedules of reinforcement and recorded the bird’s responses. Different schedules of reinforcement altered the speed, pattern, and persistence of behavior during acquisition or extinction.
In addition to pigeons, properties of behavior were examined in rats, chicks, and even turtles.   Operant conditioning applied to the actions of all organisms. “Men and women act upon the world, and change it, and are changed in turn by the consequences of their action,” Skinner remarked.  Based on his theory of feedback and learning, Skinner invented a “teaching machine” that provided a model for programmed instruction still in use today.



William James Hall
Accessible to Harvard Affiliates Only