A key attribute of his theory of cognitive development was the concept of the zone of proximal development (ZPD). Vygotsky's concept allows us to make a plausible estimate of what a child has already achieved developmentally, as well as what he or she is about to achieve, which is what he titled ZPD. Vygotsky stated that “what a child can do today with assistance, he will be able to do on his own tomorrow” (1978, p.87). Therefore, when Child Z was playing with the bark he realized that he would get it dirty (4-5), however, he was unable to mentally process that this would be an unintended consequence. Subsequently, when her father verbally explains the negative outcomes to her, she notices it (5-6). In terms of the ZPD concept, it can be implied that this interaction has led her to mature closer to a state of knowledge and understanding as to why she should not play with the cortex. Again, this is an example of the developmental benefits of allowing children to play outdoors and interact with available natural materials, regardless of possible undesirable outcomes. This Vygotskyian concept has had an influence on the development of scaffolding, which is a process that can be used to help children through their proximal area