Intelligence as a Developing Function: A Neuroconstructivist Approach

Abstract

The concept of intelligence encompasses the mental abilities necessary to survival and advancement in any environmental context. Attempts to grasp this multifaceted concept through a relatively simple operationalization have fostered the notion that individual differences in intelligence can often be expressed by a single score. This predominant position has contributed to expect intelligence profiles to remain substantially stable over the course of ontogenetic development and, more generally, across the life-span. These tendencies, however, are biased by the still limited number of empirical reports taking a developmental perspective on intelligence. Viewing intelligence as a dynamic concept, indeed, implies the need to identify full developmental trajectories, to assess how genes, brain, cognition, and environment interact with each other. In the present paper, we describe how a neuroconstructivist approach better explains why intelligence can rise or fall over development, as a result of a fluctuating interaction between the developing system itself and the environmental factors involved at different times across ontogenesis.

Keywords: development; developmental trajectory; emergent structure; individual differences; intelligence; neuroconstructivism.

Figure 1

Test-retest reliability data gathered from 34 separate studies on common IQ tests (the Standford-Binet, the WISC, the WISC-R, the WAIS, and the WAIS-R) indicate a drastic increase in reliability with age, with less stable scores in childhood and early adolescence compared to late adulthood (a). The interval between testing was another correlate of stability, with a drop in reliability as interval increases (b). Adapted and reprinted with permission from John Wiley and Sons: Journal of Clinical Psychology [40] © (1989).

Figure 2

In the study by Ramsden and colleagues [72], 33 neurologically normal adolescents had structural and functional brain scans, along with an IQ measurement (Wechsler Adult Intelligence Scale III and WISC III), at two different times (Time 1: 12–16  years old; Time 2: 15–20  years old). Results showed that changes in Verbal IQ, observed between the two time points, were positively correlated with changes in grey matter density (and volume) in a region of the left motor cortex, which is activated by the articulation of speech (a). In striking contrast, changes in Non-Verbal IQ, observed between the two time points, were positively correlated with grey matter density in the anterior cerebellum, which is associated with motor movements of the hand (b). Adapted and reprinted with permission from Macmillan Publishers Ltd: Nature [72] © (2011).

Figure 3

In a cohort of 1099 typically developing individuals between 3 and 20 years of age, parental education was found to be significantly associated with children's total cortical surface area (a) in different brain regions associated with language, reading, and various executive functions and spatial skills (b). Family income was significantly logarithmically associated with children's total cortical surface area (c) in widespread regions of children's bilateral frontal, temporal and parietal lobes (d). Adapted and reprinted with permission from Macmillan Publishers Ltd: Nature Neuroscience [127] © (2015).

Figure 4

In a large Danish sample, the association between several specific infant motor developmental milestones and adult Non-Verbal IQ was moderated by parental social status (p-values immediately after the text, represented by the symbol *, indicate the level of significance for the interaction term with parental social class). In particular, stronger associations between milestone attainment and adult intelligence in the subsample from low social status families were observed (standardized regression for milestones predicting Non-Verbal IQ are reported). Adapted and reprinted with permission from Elsevier: Early Human Development [156] © (2015).

Figure 5

The multiple interacting constraints that influence the development of intelligence, conceived as the construction of efficient mental representation (i.e., neural activation patterns that sustain adaptive behavior). The principle of context-dependence constrains intellectual development by means of three general mechanisms: cooperation, competition and chronotopy. This last mechanism reflects the developmental essence of intelligence, as constraints are supposed to operate mainly during early phases of life, with intelligence profiles expected to be more stable in adulthood compared to infancy and early childhood. Together, all constraints imposed interactively by genes, brain, cognition, and environment are viewed as responsible for the fluctuations of intelligence over developmental time.