A Critique of Discovery/Inquiry/Constructivist/Problem-Based Teaching

From the Marshall Memo #431

In this intriguing American Educator article, Richard Clark (University of Southern California), Paul Kirschner (Open University of the Netherlands), and John Sweller (University of New South Wales) ask whether people learn best when they have to discover or construct essential information, or when they are given full, explicit instruction. “Our goal in this article is to put an end to this debate,” say the authors. “Decades of research clearly demonstrate that for novices (comprising virtually all students), direct, explicit instruction is more effective and more efficient than partial guidance.” 

The authors aren’t advocating that teachers lecture all day. Explicit instruction can take many forms, they say: lectures, modeling, videos, computer-based presentations, and realistic demonstrations with ample practice and feedback, as well as class discussions and activities and small-group and independent problems and projects as a means of practicing recently learned content and skills. 

Why do the authors believe the direct approach is better than allowing students to try different approaches to solving a new math problem (for example) and debating which works best? First, research comparing the two approaches supports direct instruction; second, research on how people learn does too.

• Research comparing fully guided and partially-guided instruction – “Controlled experiments almost uniformly indicate that when dealing with novel information… students should be explicitly shown what to do and how to do it, and then have an opportunity to practice doing it while receiving corrective feedback,” say Clark, Kirschner, and Sweller. Here’s what tends to happen in discovery/inquiry classrooms: (a) only the highest-achieving and best-prepared students make the discovery; (b) many students become frustrated, disengage, or copy what the eager beavers are doing; (c) some students “discover” an incorrect solution and cling to it even after being told the correct answer; (d) even if all students find the correct answer through discovery, it takes two or three times longer than direct instruction with practice and feedback; and (e) indirect instruction widens the achievement gap because better-prepared students learn much more from inquiry learning than less-prepared students. 

What has led so many educators to believe that discovery teaching works is the constructivist teaching fallacy. “Simply put,” say the authors, “cognitive activity can happen with or without behavioral activity, and behavioral activity does not in any way guarantee cognitive activity. In fact, the type of active cognitive processing that students need to engage in to ‘construct’ knowledge can happen through reading a book, listening to a lecture, watching a teacher conduct an experiment while simultaneously describing what he or she is doing, etc. Learning requires the construction of knowledge. Withholding information from students does not facilitate the construction of knowledge.” 

Curiously, if given a choice, lower-performing students prefer discovery learning and higher-performing students prefer explicit instruction – in both cases, they’re picking the approach that does them the least good!

• Research on how people learn – Recent studies have established the key role of long-term memory in how well we function in cognitively based activities – everything from crossing the street in traffic to solving math problems. Chess masters are able to play several games at once because they have memorized thousands of board configurations and remember the best moves in each situation. Long-term memory is the ultimate aim of teaching: “Everything we see, hear, and think about is dependent on and influenced by our long-term memory,” say the authors. “If nothing has been added to long-term memory, nothing has been learned.” 

Working memory, on the other hand, is a limited mental “space” in which conscious processing occurs – in other words, in which we think. “The relations between working and long-term memory, in conjunction with the cognitive processes that support learning, are of critical importance to developing effective instruction,” say Clark, Kirschner, and Sweller. Short-term memory can hold only about seven items at a time, only two or three can be processed simultaneously, and almost all the information stored there is lost within 30 seconds.

“The limitations of working memory only apply to new, to-be-learned information,” say the authors. “When dealing with previously learned, organized information stored in long-term memory, these limitations disappear.” There are no known limits to how much information can be brought into working memory from long-term memory.

“These two facts – that working memory is very limited when dealing with novel information, but that it is not limited when dealing with organized information stored in long-term memory – explain why partially or minimally guided instruction typically is ineffective for novices,” say the authors, “but can be effective for experts. When given a problem to solve, novices’ only resource is their very constrained working memory. But experts have both their working memory and all the relevant knowledge and skill stored in long-term memory.” 

One of the best examples of instruction that takes advantage of these insights is the “worked example” approach – a problem that has already been worked out is explained step by step. Numerous studies in math, science, English literature, and world history classrooms have shown that this approach is most effective with novice learners because it reduces the overload on working memory and allows students to stay on top of the problem-solving process. Most important, it allows students to direct working-memory resources toward storing the essential problem-solving steps in long-term memory. “Students learn to recognize which moves are required for particular problems,” say the authors, “which is the basis for developing knowledge and skill as a problem solver.”

For experts, on the other hand, the worked-example approach is redundant and ineffective. For them, solving a problem is more effective because they can retrieve problem-solving steps from long-term memory. The authors call this the “expertise reversal effect” – simply put, “instructional effects that are highly effective for inexperienced learners can lose their effectiveness and even have negative consequences when used with more experienced learners.” 

“Putting Students on the Path to Learning: The Case for Fully Guided Instruction” by Richard Clark, Paul Kirschner, and John Sweller in American Educator, Spring 2012 (Vol. 36, #1, p. 6-11), http://www.aft.org/pdfs/americaneducator/spring2012/Clark.pdf