We appreciate that Kline brings out the differences in the functionalist, mentalistic, and culture-based definitions of learning. We agree that much can be gained by comparing and unifying the three approaches to learning.

We also appreciate Kline's attempt to categorize the different forms of teaching. We agree that such a categorization will be useful for animal researchers when analyzing to what extent teaching occurs in particular species. However, the transitions between different forms of active teaching may be strongly correlated with the evolution of language. From an evolutionary point of view, it is important to keep the forms of teaching that require language separate from those that do not. Kline's category “direct active teaching” is too broadly defined to take this into account, and needs to be divided into subcategories. In particular, teaching by demonstration can be accomplished without verbal instruction, whereas explaining causal relations and narrating cannot. To give two archaeologically relevant examples, teaching how to produce a simple stone tool (Stout Reference Stout2011) or how to cook tubers (Wrangham Reference Wrangham2009) can presumably be achieved without symbolic language (gestures may be required, though).

Another shortcoming in Kline's list is a lack of definition of teaching for innovation, where the pupil becomes prepared to go beyond what is taught. Kline focuses on teaching as instructions, rectifications, repetitions, and so on, with the purpose of having the learner repeat what is taught. But reducing teaching (and learning) to such a perspective results in one form of teaching vital for hominid evolution not being discussed; that is, teaching with the purpose of making the learner achieve the capacity to arrive at independent conclusions resulting in new knowledge and skills not previously known. This form of teaching has enriched the learning environment of future generations throughout human evolution, transforming human cognition and social life (Sterelny Reference Sterelny2012).

Our main problem with Kline's article, however, is the lack of evolutionary mechanisms that can explain the uniqueness of human teaching. In section 7, she speculates about why active teaching appears to be limited to humans. Her first suggestion is that other species may actually use active teaching. In order to test this, we submit that it is necessary to more finely partition the notion of active teaching, as we suggest above. It is possible that teaching by demonstration may be found in other species, but hardly any teaching that requires symbolic communication. The only purported example of active teaching in another species is Boesch's (Reference Boesch1991) description of chimpanzee mothers showing their offspring how to crack nuts, which indeed is an example of teaching by demonstration.

Kline's second suggestion is that teaching is uniquely human because of our capacities for theory of mind or metacognition. We find her analysis of theory of mind and its relation to teaching wanting. “Theory of mind” is not a unitary capacity, it can be broken down into understanding the emotions, attention, intentions, and beliefs (or knowledge) of others (Gärdenfors Reference Gärdenfors2003; Reference Gärdenfors, Liljenström and Århem2007). It is important to notice that the different types of teaching that Kline proposes presume different forms of theory of mind. For example, teaching by evaluative feedback requires that the pupil understands the emotions of the teacher, but it does not require understanding the beliefs of the teacher. Similarly, teaching by demonstration, which we propose as a subtype of direct teaching, presumes that the pupil understands the intentions of the teacher, but, again, not the beliefs of the teacher. The upshot is that theory of mind in the form of understanding the beliefs of the teacher (the form tested in false-belief tasks) is required only for the most advanced types of teaching.

Kline's third suggestion for why directive active teaching is observed only in humans is that “ours is the only species in which it is adaptive” (sect. 7, para. 6). Her argument for this is that humans evolved in “the cultural niche” and that active teaching coevolved with culture. In order to evaluate this argument, it is, again, necessary to distinguish several forms of direct teaching.

The data Kline presents to illustrate the different forms of teaching come from (mainly her own) anthropological studies and from research on animals. Hominin cognition and technology have coevolved for at least 2.6 million years, and we submit that Kline's data should be complemented by an analysis of archaeological material, with respect to which forms of teaching the technologies require for their transmission over generations. For example, some forms of early lithic technology seem to require teaching by demonstration, but not symbolic communication (Stout Reference Stout2011). If this is correct, several levels of “cultural niches” have existed during the hominin evolutionary line. Thus, the “cultural niche” is no unitary phenomenon, but rather something that has developed gradually in various contexts at different times, and not in a linear fashion (Lombard Reference Lombard2012). Kline is presumably correct when she suggests that direct active teaching coevolved with culture, but this suggestion must be fleshed out with a description of the evolutionary mechanisms that are involved.