Subsequently CAT has been influenced by ideas from the work of Vygotsky and Bakhtin. From Vygotsky come concepts such as the zone of proximal development (ZPD) and scaffolding. The ZPD implies that new tasks set for the patient (for example, tolerating anxiety about social situations) should extend what they do beyond their current capabilities, but only by a small and achievable amount. Scaffolding involves the therapist providing support for the patient's efforts to change, but varying this level of support as the patient's needs change.