A worker receives difficult feedback just before leading a meeting. One possible response is to insist that anxiety must disappear before speaking. Another is to notice it, choose what the meeting requires and ask for support where the task exceeds available capacity. The second response may be called psychologically flexible, but that phrase needs care. It does not mean accepting every demand, feeling calm in every situation or being endlessly adaptable for an employer. It concerns the fit between a person’s responses, the situation and the purposes the person can endorse.
This research brief examines psychological flexibility as a model of behavioral health, with Kashdan and Rottenberg’s 2010 review as a central source and the acceptance and commitment therapy, or ACT, literature as an important related tradition. The canonical handoff title names a broad idea rather than one exact paper title. Its two later Nature seed links concern resilience and well-being interventions more generally, so they should not be mistaken for direct tests of this particular construct. The primary question here is what the model proposes, how flexibility has been measured and what intervention evidence can and cannot establish.
What the model proposes
Kashdan and Rottenberg argued that psychological health cannot be described only by a stock of positive thoughts or traits. People encounter situations that change, goals that conflict and emotions that do not obey a plan. Their 2010 review treated flexibility as the capacity to notice situational demands, shift ineffective responses, balance domains of life and act in ways aligned with important values. This is a conceptual synthesis across research traditions, not a trial showing that one technique cures a condition.
Context is the central word. The same behavior can be useful in one situation and costly in another. Persisting through a hard lesson can be valuable when the lesson matters and help is available. Persisting with an unsafe workload can deepen harm. Leaving a stressful conversation may be avoidance when it prevents a needed repair, or protection when the conversation is threatening. A model that labels behavior flexible or inflexible without knowing the situation has lost what it was meant to explain.
The review also linked flexibility to awareness, openness and goal-directed action. A person might notice a painful thought without treating it as an absolute command, then choose an action that serves a relationship or task. That description should not become a demand to tolerate injustice. The person’s goals and material options matter. Flexibility is not compliance with whichever institution has more power.
How ACT gives the idea a process model
Hayes, Luoma, Bond, Masuda and Lillis’s 2006 paper described the model, processes and outcomes of ACT. Its account emphasizes psychological flexibility through processes such as acceptance, cognitive defusion, attention to the present, perspective on the self, values and committed action. These processes are proposed to help a person act effectively in the presence of thoughts or emotions that cannot simply be removed. The model belongs to a treatment tradition and should be read alongside its empirical tests, not as proof by definition.
Acceptance is often misunderstood as approval. In the ACT model, it concerns making room for experiences that are already present when fighting them would narrow action. A person can accept the fact of anxiety while refusing an unsafe workplace rule. Cognitive defusion means relating differently to a thought, rather than proving it false by force. A worker might notice “I will fail” as a mental event and still prepare for the meeting. Neither process replaces planning, training or institutional protection.
Values in this model are chosen directions rather than external performance targets. “Be a caring parent” is a direction that can guide many acts; “never miss a school event” is a rigid rule that may conflict with illness, work and another child’s needs. Committed action is not relentless motion. It can include seeking help, revising a plan or stepping away from a harmful context. The useful test is whether the action serves a meaningful purpose under real conditions.
Kashdan and Rottenberg’s broader formulation and the ACT model overlap but are not identical. The former brings together diverse flexibility constructs, while ACT offers a specific therapeutic process account. A source-first page should avoid collapsing all evidence about emotion regulation, coping, goal adjustment or ACT into one identical phenomenon. Similar language across studies does not guarantee comparable measures or mechanisms.
What was actually measured?
A concept as broad as flexibility is difficult to observe directly. Researchers often use questionnaires about willingness to experience difficult thoughts and feelings, valued action or avoidance. Some studies use the Acceptance and Action Questionnaire-II, known as AAQ-II. A low or high score can be useful within a study, but it is not a direct observation of every decision a person makes. It can also overlap with measures of distress.
Cherry and colleagues’ 2021 scoping review found 23 flexibility-related constructs across 220 articles and assessed 12 prominent measures. They reported definitional overlap as well as disagreement, and they criticized problems with common use of the AAQ-II. Their conclusion was not that flexibility is meaningless. It was that better definitions and measures are required before different studies can be compared confidently. A broad model may be valuable while its operational tools remain contested.
Research specifically on AAQ-II discriminant validity has argued that the scale can be difficult to distinguish from negative affect or psychological distress. If a participant’s distress falls during treatment and their AAQ-II score improves, the two changes may partly reflect shared item content rather than proof that flexibility was the causal mechanism. Other researchers have tested alternative interpretations and measures. This is an active measurement debate, not a settled reason to discard all flexibility research.
Measurement should follow the claim. If the question is whether someone can adjust a coping strategy when circumstances change, observe strategy selection across situations. If the question is whether they can act on a chosen value despite discomfort, use measures that capture that action and context. If the question is symptom relief, measure symptoms directly. A single questionnaire score should not be treated as a complete account of behavioral health.
Repeated observation could make the model more precise. A researcher might ask participants about a difficult event, the options they perceived, the action they took and whether it served a stated value, then follow them over time. This would still depend on careful interpretation: people may not know every influence on their choice, and a value stated in a questionnaire may change. But it would locate flexibility in a sequence of situations rather than assume that one stable score tells the whole story. Behavioral tasks and accounts from affected people can add perspective when they are collected ethically.
What intervention research adds
ACT studies test whether a package of therapeutic practices helps people with defined problems. A 2024 systematic and meta-analytic review examined psychological flexibility and inflexibility as possible treatment mechanisms in ACT. The authors recommended measuring these as related but distinct processes, using multidimensional scales, and collecting repeated observations during treatment to test temporal order. That recommendation acknowledges a common limit: even when symptoms and flexibility measures improve together, one change may not have caused the other.
Trials and reviews of ACT report benefits for some outcomes and populations, but effect size and comparator matter. Improvement against a waitlist is not the same evidence as improvement against another credible treatment. A benefit in one clinical group does not justify claims about every workplace, school or person under stress. Treatment packages also include therapist contact, expectations, practice and social support. The flexibility model helps specify candidate mechanisms, yet a whole-package trial cannot isolate a single process unless its design tests it.
The 2024 mechanism review urged researchers to include well-being outcomes such as vitality and connectedness, not only symptom scores. This matters for a behavioral-health model because functioning includes what a person can do and how life is organized. Still, a measured increase in valued action can be hard to interpret if the person’s opportunities have changed at the same time. An intervention that teaches acceptance while leaving a harmful environment untouched may appear successful on one scale and fail a fuller ethical assessment.
Where the model helps in ordinary life
Consider a student who avoids asking a question because embarrassment feels unbearable. A flexibility-informed response may help the student notice the feeling, identify what learning requires and ask one small question. The relevant outcome is not whether embarrassment disappears. It is whether the student can act in line with a learning purpose while having enough safety and support to do so. If the classroom punishes questions, the environment must change too.
Consider someone recovering from illness. They may need to adjust plans as energy varies without concluding that every adjustment is failure. The model can help describe a difference between chosen adaptation and rigid self-judgment. It cannot supply a medical plan or determine what level of activity is safe. That requires clinical information and the person’s own priorities. Psychological flexibility should never be used to pressure someone to perform beyond a health limitation.
For an organization, the model may encourage a manager to ask which goals are fixed and which methods can change. But the organization should not turn “be flexible” into a one-way demand on workers. A genuinely flexible system can adjust workloads, deadlines and accommodations. If only the person with least power must adapt, the model has been detached from context and used as a slogan.
Context includes power, culture and material conditions
People differ in the options available to them. A secure employee may be able to refuse a late meeting; a precarious worker may not. A caregiver may have little time for a recommended practice. Cultural norms also shape how values, emotion and acceptable action are described. A scale developed in one language or setting may not have the same meaning elsewhere. A careful study should examine whether its measure works across groups before comparing scores as if they were interchangeable.
Longitudinal and intervention designs can clarify whether flexibility precedes later health outcomes, but they must account for changing circumstances. A person may score as more flexible after a new job, financial security or supportive relationship. A simple model attributing improved health only to an internal skill would miss those causes. The 2026 organizational scoping review likewise called for clearer construct definitions, stronger longitudinal designs and broader occupational and cultural representation. This is especially relevant when research moves from therapy into workplaces.
Flexibility is sometimes framed as the opposite of consistency. That is misleading. Stable values can guide different actions as circumstances change. A person might speak firmly in one setting and listen quietly in another while remaining committed to fairness. Conversely, constantly switching plans because of outside pressure may indicate loss of agency rather than health. The model’s strength lies in matching action to context and purpose, not praising change for its own sake.
There is also a difference between flexible behavior and an institution’s demand for flexibility. The former asks whether a response fits a person’s situation and values. The latter can mean accepting an unpredictable schedule, unpaid work or the withdrawal of support. A study that asks only whether workers report coping better could miss a worsening of their conditions. Research and practice should record both sides of the relationship: the person’s available responses and the environment that makes some responses costly or impossible.
What the evidence does not show
The 2010 Kashdan and Rottenberg article is a conceptual review. It does not establish a single causal pathway from flexibility to health, and it does not identify one universal score for the construct. Hayes and colleagues’ ACT model describes proposed processes; it should not be treated as proof that those processes mediate every treatment result. The 2024 mechanism review itself calls for better repeated measurement and comparison of flexibility with inflexibility and nonspecific factors.
The AAQ-II debate means that a questionnaire change cannot automatically be read as a change in the precise capacity the theory names. Distress, context and wording may affect scores. Evidence about ACT interventions cannot be generalized without attention to population, comparator, treatment quality and outcome. The later Nature handoff seeds concern broader resilience and well-being evidence, not direct validation of this brief’s central model.
Most of all, psychological flexibility does not mean people should accept avoidable harm. In some settings, the adaptive response is to challenge a rule, seek an accommodation, leave an unsafe situation or ask an institution to change. A behavioral-health model that ignores available resources and power cannot describe the conditions under which a choice is truly possible.
Return to the meeting
The worker may still feel anxious. She can prepare, ask a colleague to share part of the meeting, clarify what the feedback means or decide that the workload needs renegotiation. Different actions could be flexible depending on the stakes, support and values involved. The model is useful if it opens that inquiry. It becomes harmful if it supplies one compulsory answer: endure more.
Psychological flexibility is best treated as a research program and a practical question about fit. What response is possible here, what purpose does it serve and what conditions would make a better response available? The answer belongs partly to the person and partly to the world that constrains or supports them. That is why a source-led account of behavioral health must keep the measurement debate and the institutional context in view.
Research references
- Kashdan, T. B., & Rottenberg, J. (2010). Psychological flexibility as a fundamental aspect of health. Clinical Psychology Review, 30(7), 865–878. View source
- Hayes, S. C., Luoma, J. B., Bond, F. W., Masuda, A., & Lillis, J. (2006). Acceptance and commitment therapy: Model, processes and outcomes. Behaviour Research and Therapy, 44(1), 1–25. View source
- Cherry, K. M., Vander Hoeven, E., Patterson, T. S., & Lumley, M. N. (2021). Defining and measuring “psychological flexibility”: A narrative scoping review of diverse flexibility and rigidity constructs and perspectives. Clinical Psychology Review, 84, 101973. View source
- Macri, J. A., & Rogge, R. D. (2024). Examining domains of psychological flexibility and inflexibility as treatment mechanisms in acceptance and commitment therapy: A comprehensive systematic and meta-analytic review. Clinical Psychology Review, 110, 102432. View source
- Roche, M., et al. (2026). A scoping review and research agenda: Psychological flexibility and wellbeing in organisations. Applied Psychology: Health and Well-Being. View source
- Wolgast, M. (2014). What does the Acceptance and Action Questionnaire (AAQ-II) really measure? Behavior Therapy, 45(6), 831–839. View source