Jean Piaget
Did he do a Science of Developmental Psychology?

Psychology is a science! You’ll hear us say, over and over. So much so, we have a joking cliche - Psychology has Physics Envy - a play on a Freudian idea. You would be hard-pressed to find a psychology professor defending Sigmund Freud. Rightfully so. But sometimes Jean Piaget is treated as similarly unscientific. Afterall, his theory is dated, it’s wrong, and his methods weren’t as rigorous as we expect today. Why waste time learning about Piaget’s Theory or covering it in Developmental Psychology class? These are statements and questions of psychology professors!

I would like to counter. In actuality, phenomena Piaget observed are surprisingly replicable and, while his model includes more leaps than we would make today, he was scientifically rigorous. Our efforts to understand his work tell us something important about our present-day scientific efforts and help our students appreciate scientists’ struggle I hope you come to see why, whenever I choose a Developmental or Introductory Psychology class textbook, the first thing I check is how the author differentiates Piaget and Freud.

Probably the biggest complaint of developmental psychologists about Piaget’s methods is his study of his own three children. On the surface, his work resembles the pseudoscience of Freud, who built his developmental theory on six case studies. Neither is nearly a representative sample. But look deeper. Freud’s case studies are his clients - all adults - and he dramatically interprets how he understands those clinical sessions to explain childhood. Freud is the sole interpreter of his data and he even destroyed his contemporaneous notes preventing anyone from providing an alternative explanation.

Piaget (1952) reports his observations of his children throughout their infancy in his book, The Origins of Intelligence. He meticulously describes tasks he created in ways anybody can replicate. I have! Piaget has many tasks tracing the development of particular abilities like object permanence (figure 1). I adapted Piaget’s means-ends sequencing task for my masters thesis and dissertation (Grobman, 2002; Grobman, 2003). When I give infants his original version, I get the same patterns he did.¹ How often do we have such replicable patterns in our results?

Piaget studied children beyond his own family too. For example, Bärbel Inhelder and Jean Piaget’s (1964) Early Growth of Logic in the Child, they explained children’s understanding of class membership and categories (like Venn diagrams). On page 121, he provides a table summarizing data just like we do today. He studied 44 children in 3 age-groups responding to two versions of the same task. That is, a within-subject experimental manipulation to test a hypothesis.

Piaget built a lot of his theory with small sample sizes. While not ideal, it is not inherently unscientific. For example, Hermann Ebbinghaus (1885) discovered the forgetting curve with a sample of one - himself. While Piaget’s interpretations may be leaps, they are not such large ones, as he finds many tasks of different constructs yielding patterns fitting his model (e.g., object permanence and means-ends sequencing tasks show the same patterns of circular reactions).

Jean Piaget created dozens of tasks, others have replicated his results, and some have newer interpretations. For example, Renee Baillergeon (1987) suggests Piaget's Object Permanence tasks were too complicated and she offers another method, based purely on looking-time, to suggest 3 to 4 year olds have abilities Piaget only ascribes to 8 to 12 month olds. Baillergeon has a point. But I feel we’re too quick to dismiss Piaget’s account as simply wrong and outdated. For example, performance on Piaget’s object permanence tasks have sensible correlations with language acquisition (Gopnik & Meltzoff, 1986) and separation anxiety (Lester et al., 1974). In sharp contrast, looking-time based tasks of Baillergeon and others are like an island in the field of developmental psychology, without much meaningful tying it to other methods, ages beyond infancy, and aspects of infancy observable differently.

Many more people have given other accounts to explain Piaget’s results, including Adele Diamond (1985) using memory and inhibition and me using domain general problem solving strategies. Maybe another model will surpass Piaget’s. Actually, it almost certainly will as science progresses. But even if Piaget came to incorrect conclusions, he still did science. Neils Bohr (1913) was a brilliant physicist even if his model of the atom was wrong; he did his best to explain all the evidence with a relatively simple model. Piaget did the same, and personally I feel he was just as brilliant.

Any scientist brings a perspective shaping their work. It’s where their hypotheses and research programs begin to grow. Piaget's perspective emphasizes active roles children play constructing their own understanding through mechanisms of assimilation and accommodation within their own minds to resolve disequilibrium. So an understandable criticism of Piaget with his focus inside the child is his failure to consider what’s outside the child - the social context. He’s not the only one. For example, social psychologists rarely investigate neural pathways and neuropsychologists seldom consider prejudice.

It’s a challenge adopting an entirely different point of view. Honestly, I wish we were more facile and it’s something I’m hoping to develop. I try studying different developmental approaches because each has merit other approaches struggle with. Piaget astutely distinguishes development from learning, but Information Processing captures learning and development with much greater precision. Social Cultural theorists like Vygotsky (1978) highlight mechanisms most developmental psychologists miss, probably because cross-cultural studies are difficult to conduct and it’s hard for a fish to see the role of water when water is ubiquitous.

Nevertheless, criticisms claiming Piaget ignored the social context strike me as exaggerated. He explored schools' impact on development in "Science Education and the Psychology of the Child."

Piaget and Piagetians like Lawrence Kohlberg (1981) explain girls’ slower moral development as a consequence of less sophisticated kinds of play girls with peers compared with boys. He’s using a moral measuring stick inspired by Immanuel Kant and judging girls of a boy’s play style measuring stick. Carol Gilligan (1982) extensively examines are girls are not reasoning morally, or playing, in a deficit style, but using a different voice. Piaget profoundly misses voices unlike his. In this respect he is just as biased as Freud with his bizarre untested and unfalsifiable creation of “penis envy.” Yet, even when stuck in his own perspective, Piaget nevertheless still explains gender differences with the social context - peer socialization.

While not the focus of criticism of Piaget, his theory has more gaps than culture. To my knowledge, he never considered atypical development such as how we handle mental health challenges. More broadly, he didn’t emphasize individual differences. And yet, can we name another developmental psychologist, past or present, who explores as many domains (e.g., moral, numerical, folk biology) from as many diverse perspectives (e.g., physical, adaptive, motivational, peer-related, and school-related)?

Piaget put together what he saw as the most parsimonious, simple, and complete explanation of development. He was keenly aware of scientific standards and sought to meet them. For example, he was very concerned proposing a stage theory might create unscientific teleological mechanisms to drive people through stages. It’s just so easy to turn the final stage into a goal of prior stages rather than accounting for stages with scientific mechanistic causation. Piaget studied Biology and he knew the appeal of Larmarkian Evolution (1809) and today’s “Intelligent Design.” They use teleological mechanisms because they assume a future purpose for species to change towards. In contrast, Charles Darwin's (1859) Evolutionary Theory uses natural selection, a scientific mechanistic causality explaining species adaptations from only *prior* events. Piaget wrestled with how to answer big questions of development and he never lost sight of doing that in a scientific way (see, for example, Piaget's "Insights and Illusions of Philosophy").

Instead of simply pontificating about our adult intuitions about knowledge (the traditional epistemological approach), Piaget's created a "genetic epistemology" by elaborating how our understanding of knowledge (epistemology) develops empirically - in actual people (children). In Genetic Epistemology, Piaget describes how mathematics formulates itself into structures that build upon one another. The development of our thoughts analogously builds upon one another like an axiomatic system in mathematics (figure 2). The formal operational thought adolescence is analogous to a complete axiomatic system (like Euclidean Geometry) (Euclid, 300 BCE). Piaget created developmental stages without being teleological! In sharp contrast, Freud failed to even avoid unfalsifiability - the hallmark of science.

Piaget scientifically studied children using clear operational definitions from novel tasks he created. His results are highly replicable even many decades later, even if our modern interpretations may differ. He had biases, but when we step back from our own era’s biases, we might see his theory has fewer holes than ours – especially connecting infancy with the rest of development. Piaget even philosophically addressed challenges like avoiding teleology. Yet Piaget didn’t give much attention to culture. Rather than dismiss his entire theory, we can appreciate what attention he did pay to culture sometimes, and we can expand his model with our modern appreciation of culture. We can learn a lot about developmental psychology when we learn about our field’s history, including the errors and strengths of luminary models like Piaget’s.

Baillargeon, R. (1987). Object permanence in 3½- and 4½-month-old infants. Developmental Psychology, 23(5), 655-664.

Bohr, N. (1913). On the constitution of atoms and molecules. Philosophical Magazine, 26(153), 1-25.

Darwin, C. (1859). On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. London: John Murray.

Diamond, A. (1985). Development of the ability to use recall to guide action, as indicated by infants' performance on AB-. Child Development, 56(4), 868-883.

Ebbinghaus, H. (1913). Memory: A contribution to experimental psychology (H. A. Ruger & C. E. Bussenius, Trans.). Teachers College, Columbia University. (Original work published 1885)

Euclid (300 BCE). Euclid's Elements. Retrieved from https://www.gutenberg.org/files/21076/21076-pdf.pdf

Gilligan, C. (1982). In a different voice: Psychological theory and women's development. Harvard University Press.

Gopnik, A., & Meltzoff, A. N. (1986). Relations between semantic and cognitive development in the one-word stage: The specificity hypothesis. Child Development, 57(4), 1010-1023.

Grobman, K. H. (2002). The origins and development of domain general problem solving strategies [Master's thesis, The Pennsylvania State University], https://www.researchgate.net/publication/384635556

Grobman, K. H. (2003) How social Learning opportunities and individual differences in working memory capacity contribute to the development of domain general problem solving strategies during infancy [Dissertation, The Pennsylvania State University], https://www.researchgate.net/publication/384635365

Inhelder, B., & Piaget, J. (1964). The early growth of logic in the child: Classification and seriation. Harper & Row.

Kohlberg, L. (1981). The philosophy of moral development: Moral stages and the idea of justice. San Francisco: Harper & Row.

Lamarck, J. B. (1914). Zoological philosophy: An exposition with regard to the natural history of animals (H. Elliot, Trans.). Macmillan and Co. (Original work published 1809)

Lester, O., Arkes, H., & Tukamaz, A. (1974). Psychology: A social science perspective. New York: Houghton Mifflin.

Piaget, J. (1952). The origins of intelligence in children. International Universities Press.

Piaget, J. (1971). Insights and illusions of philosophy. Routledge & Kegan Paul.

Vygotsky, L. (1978). Mind in society: The development of higher psychological processes. Harvard University Press.