Why CMO Subtypes Challenge BCBA Candidates
Among all the motivating operation concepts tested on the BCBA exam, the conditioned motivating operation subtypes cause the most difficulty. While the surrogate CMO (CMO-S) is relatively straightforward, the transitive CMO (CMO-T) and reflexive CMO (CMO-R) involve more complex stimulus relationships. Many candidates can recite definitions but struggle to apply these concepts to novel scenarios. This guide will build your understanding from the ground up with detailed examples and analysis.
The Transitive CMO (CMO-T)
Definition and Mechanism
A transitive CMO is an environmental condition or stimulus that establishes the reinforcing effectiveness of another stimulus that serves as a means to access a terminal reinforcer. The word "transitive" refers to the fact that the motivating effect passes through an intermediary. The CMO-T does not directly establish the terminal reinforcer; instead, it establishes the value of something you need to get to the terminal reinforcer.
The Classic Locked Door Example
Imagine you need to leave a room, and the door is locked. The locked door is the CMO-T. It establishes the key (or any unlocking mechanism) as a conditioned reinforcer and evokes behavior that has previously produced keys. Notice the chain of relationships: the locked door establishes the value of the key, which then allows access to leaving the room (the terminal reinforcer). Without the locked door, the key has no special reinforcing value.
Clinical Examples of CMO-T
In ABA practice, CMO-T relationships appear constantly in mand training. Consider a child who wants to play with a toy car, but it is inside a closed container. The closed container (CMO-T) establishes "help opening the container" as a reinforcer and evokes requesting behavior. The clinician might contrive this situation by placing preferred items in containers that the child cannot open independently, thereby creating opportunities for mand training.
Another clinical example: a child wants to color (terminal reinforcer) but has paper and no crayons. The presence of paper without crayons is the CMO-T that establishes crayons as a reinforcer and evokes requesting crayons. The speech-language pathologist or behavior analyst can arrange the environment to create these missing-item CMO-T conditions systematically.
The Role of CMO-T in Verbal Behavior
Sundberg (2004) extensively discussed the importance of CMO-T arrangements in teaching mands. When a learner needs something to complete a task or access reinforcement, the missing item creates a CMO-T condition that motivates communication. This is why "sabotaging" the environment (removing needed items, giving incomplete materials) is an effective strategy for evoking mands in early learners. The contrived CMO-T creates genuine motivation to communicate.
The Reflexive CMO (CMO-R)
Definition and Mechanism
A reflexive CMO is a stimulus that has been correlated with the worsening of conditions, meaning it signals that something aversive is about to happen (or something reinforcing is about to be removed) unless a particular behavior occurs. The stimulus establishes its own removal as a reinforcer. The term "reflexive" comes from the fact that the motivating effect refers back to the stimulus itself: the stimulus makes its own removal reinforcing.
The Warning Signal Example
The most common example of a CMO-R is a warning stimulus in an avoidance or escape paradigm. A teacher says, "You have 5 minutes to start your work, or you lose free time." This verbal warning functions as a CMO-R because it signals worsening conditions (loss of free time). The warning itself becomes aversive, and its removal (by starting work, which cancels the warning) functions as negative reinforcement. The student starts working to remove the threatening condition.
Clinical Examples of CMO-R
In clinical settings, CMO-R relationships are involved in many everyday interactions. A parent's "stern look" that historically precedes a reprimand functions as a CMO-R. The look establishes its own removal as a reinforcer and evokes compliance or other behaviors that have previously prevented the reprimand from following. The child complies not because the look is a discriminative stimulus for reinforcement, but because the look itself signals worsening and its removal is reinforcing.
Another example involves a timer used during behavioral interventions. If a timer counting down has historically been followed by the removal of a preferred activity at zero, the sight of the timer counting down functions as a CMO-R. It establishes the removal of the timer (or resetting the timer through compliance) as a reinforcer and evokes whatever behavior has previously stopped or reset the countdown.
Distinguishing CMO-T from CMO-R
This is where many exam candidates struggle. The key difference lies in what becomes reinforcing:
- CMO-T: Establishes another stimulus (an intermediary) as a reinforcer. The locked door establishes the key as a reinforcer.
- CMO-R: Establishes its own removal as a reinforcer. The warning signal establishes the removal of the warning as a reinforcer.
If the question describes a situation where a condition makes you need something else (a tool, a missing item, help), it is likely a CMO-T. If the question describes a condition where you want to get rid of the condition itself (a threat, a warning, an impending aversive event), it is likely a CMO-R.
Exam Strategies for CMO Questions
- Identify the terminal reinforcer: What is the individual ultimately trying to access or avoid?
- Identify the established reinforcer: What becomes reinforcing as a result of the MO? Is it another stimulus (CMO-T) or the removal of the MO itself (CMO-R)?
- Check the learning history: CMOs require a conditioning history. If the scenario involves an unlearned biological need, it is a UMO, not a CMO.
- Avoid confusing MOs with SDs: If the scenario emphasizes that a stimulus signals the availability of reinforcement for a specific behavior (rather than changing the value of a consequence), it may be describing an SD rather than a CMO.
Common Misconceptions
One widespread misconception is that every antecedent condition that precedes a behavior is a motivating operation. Many antecedent stimuli are discriminative stimuli, not MOs. The critical question is whether the stimulus changes the value of a consequence or signals the availability of reinforcement for a behavior. Another misconception is that CMO-R is simply "negative reinforcement." While CMO-R conditions often involve negative reinforcement, the CMO-R itself is the motivating operation that makes the removal reinforcing, not the reinforcement process itself.
Study these distinctions thoroughly, practice with novel scenarios, and you will be well-prepared for even the most challenging CMO questions on the BCBA exam.