Constrained and unconstrained skill development: Why it matters for secondary students

Research & Policy
Constrained and unconstrained skill development: Why it matters for secondary students

In 2005 Scott Paris wrote a paper in Reading Research Quarterly called Reinterpreting the development of reading skills. In this paper, he argued that reading researchers ignored an essential difference between constrained and unconstrained reading skills, resulting in flawed research.

Fifteen years later, the constrained/unconstrained distinction is still being used by researchers to think about the effects of early childhood literacy programs and interventions. Researchers have found the distinction helpful in thinking about why some skills are more amenable to intervention than others and why the effects of some high-impact interventions tend to “fade out” (Bailey, Duncan, Cunha, Foorman, & Yeager, 2020).

I believe that educational policymakers and leaders have not sufficiently appreciated the implications of this distinction. In this post, I examine the difference between constrained and unconstrained skills and draw conclusions about what this means for educators. In a second post, I will discuss the programmatic implications of this distinction for school leaders.

How can skills be constrained?

In the original paper, Dr. Paris identified multiple ways in which skills could be constrained along conceptual, developmental, and methodological boundaries. Three of these constraints are particularly relevant for our purposes, so I focus on scope, range of influence, and mastery.

Constraints of scope: Ranging from narrow and limited to conceptually unbounded skills

A skill's conceptual scope is probably the most important skill constraint, and it affects all the others. The scope refers to the number of elements or the set size of the skill: a skill with a small number of elements has a narrow scope and is highly constrained. For instance, in English, there are 26 letters. Knowledge of these 26 graphical forms represents a constrained and narrow learning goal. These letters singly and in combination can be used to represent 44 sounds. While knowledge of sound-symbol correspondences is a more expansive goal, it is still relatively limited in scope. Vocabulary, on the other hand, is a conceptually unbounded skill. Adult learners continue to learn new words throughout the lifespan. Similarly, content knowledge and reading ability are unconstrained in scope.

Graphic showing the continuum between highly constrained and unconstrained skills.
Constrained skills focus on a small set of elements, unconstrained skills can be conceptually unbounded

Constraints of Influence

Constrained skills can be essential, even if their influence is constrained. For instance, knowing the letters of the alphabet is a prerequisite to mastering sets of grapheme-phoneme relationships and then decoding words. Students’ literacy development can be stymied if they do not learn the names of the letters of the alphabet and this can affect their development of many other skills. However, beyond this specific role, knowing the names of the letters of the alphabet does not influence our general cognitive development. This skill acts as a bridge that takes us over a specific (and crucial) developmental boundary.

On the other hand, the influence of vocabulary knowledge is far less constrained. Vocabulary knowledge is supported by and supports linguistic, cognitive, and communicative skill development. Anyone with severely limited vocabulary knowledge could struggle in societal, social, and familial roles. This skill acts more like a pair of hiking shoes that allows us to explore our cognitive world and has broad utility.

Constrained skills explain reading performance variability in young learners. As students get older they (usually) master these constrained skills. In middle and high schools, reading ability is more associated with unconstrained skills like vocabulary and background knowledge. Given the pervasive influence of unconstrained skills, we need to ensure that our adolescent students have opportunities to develop them even if they have not met specific developmental milestones in constrained skills.

Mastery: Constraints in the ability to fully master a skill

Because of the limited scope of constrained skills, we expect our students to master them. In fact, we come to see certain milestones (like knowing all the letters of the alphabet) as age-normative skills. Educators can reference standardized criteria to identify students who are not making expected progress in their mastery of constrained skills. In contrast, there are constraints on the mastery that we can achieve in unconstrained domains. These skills continue to develop throughout the lifespan. There tends to be far greater variability in individual performance within unconstrained skills because of the wide latitude for individual specialization in skill subdomains. For instance, a student may be an expert on vocabulary associated with dinosaurs, but blissfully ignorant of the words related to tax law. No student can master all of vocabulary. Instead of assessing for mastery, we assess unconstrained domains by selected sample items to represent student overall performance. As a result, our assessment of unconstrained skills is less precise than our assessment of constrained skills.

Final remarks: a tendency to focus on constrained skills

Reading research has been dominated by the study of early reading development, and these studies have tended to focus on constrained skills. When policymakers and educators look for models of how to help middle and high schools improve literacy outcomes, they often base their thinking on work done in elementary schools focused on constrained skills. This bias has influenced our thinking about diagnostic assessments, interventions for struggling readers, and establishing multitiered systems of support (MTSS). In my next blog post, I will cover these issues in more detail.


Anderson, K. L., Atkinson, T. S., Swaggerty, E. A., & O’Brien, K. (2019). Examining relationships between home-based shared book reading practices and children’s language/literacy skills at kindergarten entry. In Early Child Development and Care (Vol. 189, Issue 13, pp. 2167–2182).

Hoover, W. A., & Gough, P. B. (1990). The simple view of reading. Reading and Writing, 2(2), 127–160.

Bailey, D. H., Duncan, G. J., Cunha, F., Foorman, B. R., & Yeager, D. S. (2020). Persistence and fade-out of educational-intervention effects: Mechanisms and potential solutions. In Psychological Science in the Public Interest (Vol. 21, Issue 2, pp. 55–97).

Paris, S. G. (2005). Reinterpreting the development of reading skills. Reading Research Quarterly, 40(2), 184–202.

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