3.2 Motivating Operations vs. Discriminative Stimuli

Defining the Motivating Operation (MO)

In behavior analysis, predicting and controlling behavior requires analyzing antecedent variables beyond the three-term contingency ($S^D \to R \to S^R$). In 1982, Jack Michael introduced the establishing operation (EO) to behavior analysis, later expanding and formalizing the concept into the motivating operation (MO) (Michael, 1993, 2000; Laraway et al., 2003).

A motivating operation is defined as an environmental event, operation, or stimulus condition that has two simultaneous, momentary effects:

1. Value-Altering Effect: An alteration in the reinforcing or punishing effectiveness of an environmental event, object, or stimulus.
   • Establishing Operation (EO): An increase in the reinforcing (or punishing) effectiveness of a stimulus.
   • Abolishing Operation (AO): A decrease in the reinforcing (or punishing) effectiveness of a stimulus.
2. Behavior-Altering Effect: An alteration in the current frequency, latency, duration, or magnitude of all behavior that has been reinforced (or punished) by that stimulus.
   • Evocative Effect: An increase in the current frequency or rate of behavior.
   • Abative Effect: A decrease in the current frequency or rate of behavior.

The Four Combinations of Value-Altering and Behavior-Altering Effects

The interaction of value-altering and behavior-altering effects produces four operational quadrants governing reinforcers and punishers:

• Reinforcer Establishing Operation (EO): Food deprivation increases the reinforcing value of food (value-altering) and immediately evokes all behaviors that have historically produced food (evocative effect).
• Reinforcer Abolishing Operation (AO): Ingestion of a massive meal decreases the reinforcing value of food (value-altering) and immediately abates all behaviors that have historically produced food (abative effect).
• Punisher Establishing Operation (EO): Sunburn increases the punishing effectiveness of high ambient heat or abrasive clothing (value-altering) and abates behaviors that produce exposure to heat or rough clothing (abative effect).
• Punisher Abolishing Operation (AO): Administration of an effective local anesthetic decreases the punishing effectiveness of dental drilling (value-altering) and evokes behaviors that previously would have been suppressed by pain (evocative effect).

It is critical to distinguish between behavior-altering effects and function-altering effects. Behavior-altering effects are immediate and momentary: they alter the current frequency of existing repertoires right now. Function-altering effects are relatively lasting changes: they alter the future frequency of the behavior under similar antecedent conditions through reinforcement, punishment, or extinction.

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Unconditioned Motivating Operations (UMOs)

Unconditioned motivating operations (UMOs) are events, operations, or stimulus conditions whose value-altering effects are phylogenically determined and do not depend on a prior learning history. Organisms are biologically hardwired to experience these states as establishing or abolishing operations.

The nine recognized human UMOs are:

1. Food deprivation
2. Water deprivation
3. Sleep deprivation
4. Activity deprivation
5. Oxygen deprivation
6. Sex deprivation
7. Becoming too warm
8. Becoming too cold
9. An increase in painful stimulation

Each item has a matching abolishing operation (for example, food satiation, getting enough sleep, warming up, or the pain ending). Other physiological states such as nausea or illness also act as motivating operations in practice, but the nine above form the standard textbook list (Cooper, Heron, & Heward, 2020).

The Learned Nature of the Behavior-Altering Effect in UMOs

While the value-altering effect of a UMO is completely unlearned (an infant does not need to learn that food is valuable when starved, or that oxygen is valuable when suffocating), the behavior-altering effect is almost entirely learned through operant conditioning. An infant initially emits undifferentiated reflex crying when food-deprived. Over ontogenetic development, operant conditioning shapes specific, highly sophisticated behavioral repertoires—such as opening a refrigerator, speaking vocal mands ("I want a sandwich"), or ordering food through a smartphone app—that are evoked when the food-deprivation UMO is active.

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Conditioned Motivating Operations (CMOs)

Conditioned motivating operations (CMOs) are motivating operations whose value-altering and behavior-altering effects are acquired ontogenically through learning and experience. Michael (1993, 2000) classified CMOs into three distinct operational subtypes: Surrogate (CMO-S), Reflexive (CMO-R), and Transitive (CMO-T).

1. Surrogate CMO (CMO-S)

A surrogate CMO (CMO-S) is a previously neutral stimulus that has been repeatedly paired temporally with another motivating operation (a UMO or an established CMO) and, through contiguous pairing, acquires the same value-altering and behavior-altering effects as the original MO.

• Clinical Scenario: A student typically eats lunch at 12:00 PM every day, experiencing physiological food deprivation. Over years of schooling, the visual stimulus of the classroom clock showing 12:00 PM is systematically paired with physical hunger. Even if the student ate a heavy mid-morning snack at 11:30 AM and is physiologically satiated, glancing up and seeing 12:00 PM on the clock establishes food as a reinforcer (value-altering) and evokes food-seeking behavior (evocative effect). In applied practice, empirical demonstrations of pure CMO-S effects remain limited in behavioral literature, but the theoretical construct explains stimulus-bound eating and environmental cue reactivity.

2. Reflexive CMO (CMO-R)

A reflexive CMO (CMO-R) is an environmental stimulus or condition that systematically correlates with the worsening or improvement of conditions over time. By doing so, it establishes its own termination, removal, or offset as a conditioned negative (or positive) reinforcer and momentarily evokes (or abates) any behavior that has successfully produced that termination.

• The Threat CMO-R (Instructional Aversion): The most ubiquitous and clinically significant CMO-R in applied behavior analysis is the "threat CMO-R." Consider a student with learning difficulties who regularly experiences academic failure, high response effort, and verbal reprimands during math instruction. When the teacher brings out the math binder and says, "Okay, time for math," that antecedent stimulus correlates with impending worsening of conditions. The presentation of the binder functions as a CMO-R: it establishes the termination or removal of the instructional demand as a powerful conditioned negative reinforcer, and immediately evokes escape-maintained behaviors (e.g., knocking materials off the desk, verbal protests, aggression).
• Applied Implications: Rather than relying on escape extinction to manage severe aggression evoked by a CMO-R, clinicians manipulate the CMO-R antecedently: incorporating demand fading, errorless teaching procedures, choice-making, and high-probability request sequences to abolish the aversive nature of the task, thereby abating problem behavior before it occurs.

3. Transitive CMO (CMO-T)

A transitive CMO (CMO-T) is an environmental event or stimulus condition that alters the reinforcing effectiveness of a second stimulus because that second stimulus is required to access an already established reinforcer. It creates a "blocked access" or "problem-solving" condition.

• Clinical Scenario: A child has an active EO for eating yogurt (food deprivation UMO). The child receives a sealed container of yogurt, but no spoon. The sealed container without an eating utensil functions as a CMO-T: it establishes a spoon (and an adult's opening assistance) as a potent conditioned reinforcer, and evokes mands for "spoon" or "open."
• Applied Implications: The CMO-T is the primary behavioral mechanism underlying incidental teaching, the interrupted chain procedure, and naturalistic mand training (Hart & Risley, 1975; Sundberg et al., 2002). Practitioners intentionally manipulate the environment—such as placing preferred items in clear, tightly sealed plastic containers, withholding an essential puzzle piece, or offering a locked toy chest—to induce a CMO-T that evokes targeted functional communication.

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Conditioned Motivating Operations (CMO) Typology

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Motivating Operations (MO) vs. Discriminative Stimuli ($S^D$)

One of the most frequent conceptual traps on the BCaBA examination is confounding motivating operations with discriminative stimuli ($S^D$). Both are antecedent environmental events that evoke operant behavior, but their behavioral functions, histories, and mechanisms are distinct.

• Discriminative Stimulus ($S^D$): An antecedent stimulus correlated with the availability of reinforcement for a specific response class. An $S^D$ acquires its evocative effect through a history of differential reinforcement: in the presence of the $S^D$, the response has produced reinforcement ($S^D \to R \to S^R+$); in the presence of the stimulus delta ($S^\Delta$), the response has encountered extinction or lower-quality reinforcement ($S^\Delta \to R \to \text{Extinction}$). An $S^D$ answers the question: "Is reinforcement currently available if I emit this behavior?"
• Motivating Operation (MO): An antecedent condition that alters the value or effectiveness of a stimulus as a reinforcer, regardless of whether that stimulus is currently available. An MO answers the question: "Do I actually want or need that reinforcer right now?"

Illustrative Clinical Vignette: The Vending Machine

Consider an illuminated vending machine stocked with cold beverages:

• The illuminated machine and the "Accepting Coins/Bills" display function as the discriminative stimulus ($S^D$). They signal that if you insert money and press a selection button, cold drinks will be delivered (differential availability: lit machine = drink available; dark, out-of-order machine = $S^\Delta$).
• However, if you have just consumed three large glasses of water and are completely satiated, you will not insert money into the machine. The illuminated machine ($S^D$) is fully present, but the behavior is not emitted because the motivating operation (water satiation AO) has abolished the reinforcing value of water and abated beverage-purchasing behavior.
• Conversely, if you have been exercising in high heat for four hours without water (water deprivation EO), the reinforcing value of water is extraordinarily high. However, if you are standing in a barren desert with no vending machine or water source present (absence of $S^D$), you cannot emit the specific coin-inserting response because the $S^D$ signaling availability is absent.

Both an active MO (EO) and an appropriate $S^D$ must be present simultaneously for an operant response to be reliably evoked in natural environments.

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Comparing MOs and Discriminative Stimuli ($S^D$)