What type of motivating operation is characterized by value-altering effects that are not learned?

Unconditioned motivating operations (UMOs) are characterized by their value-altering effects that are naturally occurring and inherent, rather than learned through experience. These operations affect the desirability of a reinforcer based on biological needs or instinctual factors. For example, hunger acts as a UMO that increases the value of food as a reinforcer. Since these operations do not require prior learning or conditioning, they can evoke behavior in a straightforward manner, making them crucial in understanding basic motivation within the context of behavior analysis.

Conditioned motivating operations (CMOs), on the other hand, rely on prior learning and experiences that teach an individual that certain conditions or stimuli can alter the value of reinforcers based on context. Surrogate and reflexive CMO types are also derived from learned associations, distinguishing them from unconditioned operations. Thus, the defining characteristic of UMOs is their innate value-altering effects, which makes the correct answer valid in this context.