Reinforcement

Reinforcement is a term used across disciplines to describe a process that increases the likelihood or effectiveness of a response, behavior, or structure by adding strength or support. In psychology and behavior analysis, reinforcement refers to consequences that increase the probability of a behavior. In engineering and materials science, reinforcement denotes additions that enhance strength, stiffness, or durability of a material or structure.

In psychology, reinforcement strengthens a behavior by presenting a favorable outcome following the behavior (positive reinforcement) or by removing an unfavorable condition (negative reinforcement). Primary reinforcers satisfy basic needs such as food or warmth, while secondary reinforcers acquire value through association, such as money or praise. Reinforcement can be contrasted with punishment, which aims to reduce a behavior, and with extinction, which diminishes a behavior by withholding reinforcement.

Reinforcement schedules describe how often and when reinforcement is delivered. Common schedules include fixed-ratio, variable-ratio, fixed-interval, and variable-interval. The rate of responding and the persistence of behavior vary with the schedule, and partial reinforcement often produces greater resistance to extinction than continuous reinforcement.

In engineering, reinforcement improves structural capacity by introducing reinforcing elements such as steel bars in concrete (rebar) or fibers in composites. Steel reinforcement carries tensile load and helps prevent brittle failure, while fiber reinforcements can provide toughness and crack control. Bonding between the reinforcement and the surrounding matrix, protection against corrosion, and adherence to design codes are important considerations. Common forms include reinforced concrete, steel-reinforced polymers, and fiber-reinforced composites. Reinforcement also covers retrofitting existing structures to resist additional loads or seismic forces.