Final answer:
Hefferline, Keenan, and Harford (1959) showed that operant conditioning, a concept studied by B. F. Skinner, could occur without awareness through the study of stress on body tension. This form of learning involves behaviors modified by their consequences, such as reinforcement or punishment.
Step-by-step explanation:
Hefferline, Keenan, and Harford (1959) demonstrated that operant conditioning could occur without awareness of the link between behavior and its consequences when they studied the effects of stress on body tension. Operant conditioning is a form of learning where the motivation for a behavior happens after the behavior is demonstrated, a concept extensively studied by psychologist B. F. Skinner. Skinner's research used a Skinner box where a rat would learn to press a lever to receive food, thereby strengthening the behavior through positive reinforcement. Hefferline and colleagues' work was significant in demonstrating that such conditioning could happen even without the subject's awareness.
Operant conditioning is not limited to physical behaviors; it also includes learning through consequences, which can be either reinforcement or punishment. Behaviors followed by satisfying consequences tend to be repeated, while those with unpleasant consequences are discouraged, a concept detailed by the law of effect. Over time, conditioning can induce animals or humans to perform learned behaviors that would not naturally occur, as seen in animal training or behavioral modification techniques.