I have a 9-month-old daughter who still cannot crawl. I’ve tried having her build up her strength through various leg and abdominal exercises. I’ve shown her interactive diagrams and YouTube videos of babies crawling, and I’ve read her the definition of crawling from the dictionary. I’ve modeled the correct way to crawl so many times I’m wearing holes in the knees of my jeans. The doctor told me that this is totally normal and not to worry, but today when I put her down in the crawl position, she was totally hopeless. Please help!

– Zach Groshell

Before this blog gets flooded with comments either a) kindly informing me that she is well within the normal age range to not have crawled or b) making fun of my parenting, let me clear that I am being facetious. I, like most people, understand that no amount of instruction will teach my baby how to crawl; It will come naturally, when she’s ready. It would be just as silly to try to teach her how to coordinate her lips, tongue, alveolar ridge, and breath in order to try to get her to speak (Paas & Sweller, 2012). As a typically developing child, she will learn to speak at about the same time as all other typically developing children – naturally, effortlessly, through simple membership in English–speaking society.

Why is this the case? The basic answer is that we’ve evolved to be able to crawl, walk, and speak, and acquire a number of other abilities naturally, without instruction. In this post, I would like to share an especially useful theory of knowledge categorization that was featured in one of my recent workshops, but that seems mostly unknown to teachers; Biologically primary and biologically secondary knowledge (Geary, 2008). While it is not a “finished” theory, it can help teachers and leaders in education to distinguish between that which is best learned unconsciously and naturally, and that which requires formal instruction.

Biologically Primary Knowledge

Imagine the most remote, isolated tribe of peoples, inaccessible by plane, train, or automobile, cut off from modern-day amenities like TikTok and Amazon Prime. We can be certain that, despite there not being any formal system of schooling or access to instructional texts in this society, every member of this tribe will learn to walk and speak their native language. We can also expect that children in this society will quickly learn to discriminate between faces and organize themselves into cooperative groups (Geary, 2008). We have evolved to be able to rapidly and effortlessly acquire this kind of knowledge, biologically primary knowledge, because without it the chances of survival, stability, and reproduction would be greatly reduced. As teachers, we can expect that a policy of “just let kids be kids” will be sufficient to teach biologically primary knowledge for all typically developing children. In effect, the classification of knowledge into the two categories of biologically primary and biologically secondary knowledge provides the ultimate justification for play-based learning in the early years of schooling, because by depriving children of opportunities to socialize with each other and play with tools, we may be stunting their acquisition of non-instructable foundational knowledge.

Humans across all tribes and all societies, regardless of their level of modernization or economic development, have evolved to acquire, and will acquire, biologically primary knowledge. What, then, is biologically secondary knowledge?

Biologically Secondary Knowledge

While it would be pointless, and frankly, bizarre to attempt to teach biologically primary knowledge to children through formal instructional methods, such as through lecture or by providing worked examples, a great deal of knowledge that we require to function in developed society must be taught (Tindall-Ford, Agostinho, & Sweller, 2019). This sort of knowledge is known as biologically secondary knowledge, and examples include practically any academic skill, such the knowledge of how to read, write, and solve math equations. Biologically secondary knowledge, while essential for getting a job or comprehending a newspaper in today’s world, constitutes knowledge that was only relatively recently invented in human history and isn’t guaranteed to be present across all cultures and societies; Some societies have never developed a system of writing for their language and many cognitively able adults are illiterate. Unlike biologically primary knowledge, biologically secondary knowledge isn’t strictly necessary for our survival, so we have not evolved to acquire it effortlessly through immersion or osmosis.

Acquiring a strong grasp of the correspondence between letters and their sounds in an alphabetic writing system (i.e. phonics) is a prime example of something that we have not evolved to learn, and therefore must be taught. We know that simply placing texts around a child’s environment and modeling the attitudes of a reader is not enough to teach a child to decode words; We must pass on the knowledge of letter-sound correspondences of a written language to our students through instruction. We cannot expect that the same strategies that work for learning to speak a first language fluently (i.e. play, discovery, and social interaction) will work to teach students to read, write or solve math problems fluently.

The role of schools is, therefore, to teach biologically secondary knowledge so that the next generation can inherit that which we have not evolved to learn naturally. Instructional design is effectively a field concerned with the design of “unnatural” instructional procedures for the teaching of biologically secondary knowledge that comply with what we know about the capabilities and limitations of the human cognitive system (Paas & Sweller, 2012).

As teachers, we should be content with our role in teaching domain-specific biologically secondary knowledge, and reject the arguments from snake oil-peddling education “gurus” that academic learning should be natural and “when they’re ready.” If we haven’t evolved to learn an element of the curriculum naturally and without effort, then the strategy of letting “kids be kids” so that they might magically pick it up through osmosis will not work. It would be just as awkward, bizarre, and pointless to attempt to teach a student advanced algebra through free play and unguided discovery as it would be to try to teach my daughter to crawl through instruction. 

– Zach Groshell, tweeting @mrzachg


Geary, D. C. (2008). An evolutionarily informed education science. Educational Psychologist, 43(4), 179–195. https://doi.org/10.1080/00461520802392133

Paas, F., & Sweller, J. (2012). An Evolutionary Upgrade of Cognitive Load Theory: Using the Human Motor System and Collaboration to Support the Learning of Complex Cognitive Tasks. Educational Psychology Review

Tindall-Ford, S., Agostinho, S., & Sweller, J. (Eds.). (2019). Advances in cognitive load theory : Rethinking teaching. Retrieved from https://ebookcentral.proquest.com


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