As described above, RFT enables ACT researchers and clinicians to gain a critical understanding on how language and cognition are implicated in human psychological suffering. However, the focus of ACT is not solely on research or problem identification related to psychological inflexibility or suffering. ACT is also a science-based psychotherapeutic intervention that integrates mindfulness into change processes that promote psychological flexibility and wellbeing.

What is mindfulness

Mindfulness is a practice that has existed across different cultures, especially in Asia, as a spiritual practice (not necessarily religious) for thousands of years. In Western societies, mindfulness has become popular since the 1970s and is often adopted as a psychological intervention to address health challenges and promote health. However, within the Western science paradigms, there is still not an agreed upon definition of mindfulness. The following definitions of mindfulness may be useful in supporting our understanding of ACT mindfulness-based processes.

• Thich Nhat Hanh^[1] (2008): “I define mindfulness as the practice of being fully present and alive, body and mind united. Mindfulness is the energy that helps us to know what is going on in the present moment… Mindfulness brings concentration. When we drink water mindfully, we concentrate on drinking. If we are concentrated, life is deep, and we have more joy and stability. We can drive mindfully, we can cut carrots mindfully, we can shower mindfully. When we do things this way, concentration grows. When concentration grows, we gain insight into our lives.”
• Jon Kabat-Zinn (1994) defines mindfulness as “paying attention in a particular way: on purpose in the present moment, and non-judgmentally” (p. 4).
• Sona Dimidjian^[2] and Marsha M. Linehan^[3] (2003) conceptualize mindfulness as a set of skills that are “the intentional process of observing, describing, and participating in reality nonjudgmentally, in the moment, and with effectiveness” (p. 230).
• Ellen Langer^[4] (2000) defines mindfulness as “a flexible state of mind in which we are actively engaged in the present, noticing new things and sensitive to context,” which she distinguishes from mindlessness, when we “act according to the sense our behavior made in the past, rather than the present … we are stuck in a single, rigid perspective and we are oblivious to alternative ways of knowing” (p. 220).
• Bishop et al. (2004) developed an operationalized definition of mindfulness that consists of two parts: (1) “the self-regulation of attention so that it is maintained on immediate experience, thereby allowing for increased recognition of mental events in the present moment” and (2) “a particular orientation toward one’s experiences in the present moment, an orientation that is characterized by curiosity, openness, and acceptance” (p. 232)

See full reference on p. 116.