We applaud Kline's effort in providing a unifying framework on the social-cognitive mechanisms subserving human teaching behavior. Her approach may be seen as one of the very few attempts that not only systematize the different ways of teaching, but also examine underlying psychological mechanisms. Kline discusses the mentalistic approach in her framework. In particular, she notes that theory-of-mind (ToM) abilities are important prerequisites for human learning and teaching (see also Sodian & Frith Reference Sodian and Frith2008). Although we agree on the author's evaluation of the role of ToM in teaching, we think that the discussion of the psychological mechanisms remains too sketchy to generate novel research and, therefore, needs further extension. We will demonstrate this with the following two points: First, the mentalistic approach does not fully capture teaching behaviors in young children. Second, teaching, even by adults, at times can be unconsciously and implicitly employed in human interactions. We discuss these points in more detail next.

As Kline points out well in her article, according to the mentalistic approach theory of mind plays an important role in human teaching. Yet, recent empirical studies provide some evidence that – even in situations that require an understanding of others' knowledge state –ToM abilities may not be sufficient enough to explain children's selective teaching behaviors (Kim & Spelke Reference Kim and Spelke2013; Kim et al., in press). For example, Kim and Spelke (Reference Kim and Spelke2013) reported that 4- to 8-year-old children were presented with two characters: one, knowledgeable and, the other, ignorant. In one task, they had the chance to ask one of the characters for information. As expected from the ToM literature, by 4 years – the age at which children already have an understanding of the difference between knowledge and ignorance – children did selectively consult the knowledgeable person. By contrast, when children were asked to teach one of the characters about the information they knew, it was only at around 7 and 8 years old that children reliably chose to teach the ignorant person. These findings suggest that ToM abilities are not sufficient for the development of selective teaching. Rather, an understanding of another's knowledge states needs to be complemented by additional, and perhaps even independent, psychological processes, in order to produce selective teaching behaviors. Together, although Kline reserves a place for mentalistic processes in her framework, it seems to lack a deeper appreciation of the specific psychological mechanisms involved in selective and efficient teaching.

In other circumstances, teaching can be rather automatically and naturally enacted in human interactions in which psychological mechanisms other than mentalistic ones are responsible for adaptive teaching behavior. One recent approach, also mentioned by Kline, assumes teaching to be an evolutionary adaptation that operates on the basis of non-mentalistic and subconscious processes (Csibra & Gergely Reference Csibra and Gergely2009). Another, even more parsimonious approach with respect to the cognitive prerequisites subserving teaching, originates from the study of parent–infant interactions. Developmental literature has provided ample evidence that caregivers automatically demonstrate novel actions in a way that allows infants to recognize and process the central elements of observed behaviors. More specifically, the concept of “motionese” has been used to describe parents' inclination to demonstrate actions with greater enthusiasm, a slower motion rate, simplified sequences, and in a more punctuated manner (e.g., Brand et al. Reference Brand, Baldwin and Ashburn2002). These demonstrations by caregivers have been shown to facilitate imitative learning in young children (Williamson & Brand Reference Williamson and Brand2013). Further support for these findings comes from studies demonstrating how mothers' sensitivity relates to infants' understanding of others' behaviors (Licata et al. Reference Licata, Paulus, Thoermer, Kristen, Woodward and Sodian2014). It is likely that, via this kind of simplified action demonstration, parents actually tune into their infants' motor system, that is, they demonstrate the actions that resemble how infants themselves might perform these actions. This might help infants to relate the observed behavior to their own restricted motor repertoire (Paulus Reference Paulus2014), subsequently supporting imitative learning (Paulus et al. Reference Paulus, Hunnius, Vissers and Bekkering2011, Reference Paulus, Hunnius and Bekkering2013). Given that these behaviors seem to be quite automatic and not based on mentalistic reasoning, these findings provide further evidence for the claim that mentalistic reasoning may not be necessary for all forms of teaching. Yet, Kline's proposal does not specify the exact psychological processes that subserve these implicit forms of teaching behavior.

In short, although we applaud Kline for taking up the challenge and for presenting a theoretical framework of human teaching, we believe that her account must be elaborated by specifying the exact psychological mechanisms subserving human teaching. Such a model would provide testable predictions that could stimulate further research.