Abstract
Integration/differentiation of mental processes is major mechanism of development. Developmental theories ascribe intellectual development to it. In psychometric theory, Spearman’s law of diminishing returns postulates that increasing g allows increasing differentiation of cognitive abilities, because increased mental power allows variable investment in domain-specific learning. Empirical evidence has been inconsistent so far, with some studies supporting and others contradicting this mechanism. This state of affairs is due to a developmental phenomenon: Both differentiation and strengthening of relations between specific processes and g may happen but these changes are phase-specific and ability-specific, depending upon the developmental priorities in the formation of g in each phase. We present eight studies covering the age span from 4 to 85 years in support of this phenomenon. Using new powerful modeling methods we showed that differentiation and binding of mental processes in g occurs in cycles. Specific processes intertwine with g at the beginning of cycles when they are integrated into it; when well established, these processes may vary with increasing g, reflecting its higher flexibility. Representational knowledge, inductive inference and awareness of it, and grasp of logical constraints framing inference are the major markers of g, first intertwining with in their respective cycles and differentiating later during the periods of 2–6, 7–11, and 11–20 years, respectively. The implications of these findings for an overarching cognitive developmental/differential theory of human mind are discussed.
Highlights
More than a half a century ago, Lee Cronbach [1] set a major goal for psychology: To integrate experimental psychology, which studies lawful relations between processes, with correlational psychology, which studies individual differences in processes, into a unified discipline that would allow predictions of “the behavior of organism-in-situation” (p. 682)
The contribution of the executive processes diminishes and the contribution of the cognizance and inference increases with age as the first automate and the second are increasingly needed to handle the increasing multiplicity of the representations mediating between the individual and the world.” [7]
This article focuses on a long-debated issue in the psychology of intellectual development and individual differences: Are special mental processes differentiated from or integrated with general mental ability as general mental ability or age increases? We present a series of studies answering this question for a succession of developmental periods spanning from 4 through
Summary
More than a half a century ago, Lee Cronbach [1] set a major goal for psychology: To integrate experimental psychology, which studies lawful relations between processes, with correlational psychology, which studies individual differences in processes, into a unified discipline that would allow predictions of “the behavior of organism-in-situation” (p. 682). 2017, 5, 23 age differences and within-age individual differences in intelligence are systematically connected to the state and operation of several mental processes. These relations will be outlined below, it is beyond the aims of this article to exhaustively review or evaluate this research (see [2,3,4,5]). We will build on what seems to be common ground in order to highlight how processes interact in development, causing deep changes in how the human mind operates in different phases of life
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