Nature v. Nurture in the Lifespan Development of People with Down Syndrome

In this article, passive and active genotype -> environment effects in general and related to the cognitive development of people with Down syndrome (DS) are discussed. An emphasis is put on the high variability in profiles of DS, as well as on the existence of multiple intelligences such as musical, spatial, interpersonal, and naturalist abilities, although these are not included in traditional IQ tests that measure mainly linguistic and logical-mathematical abilities only. Also, intelligence is not fixed, it, however, defines a certain reaction range of possibilities. Neural plasticity, children’s universal desire to learn, and the importance of early guided participation of parents make clear that human beings are also the result of how they were brought up. In conclusion, it is less about nature VERSUS nurture than about nature AND nurture in human development.

Down syndrome (DS) is a genetic issue caused by an additional copy of the 21st chromosome [1] and is a neurocognitive and behavioral development disability that includes verbal and attention deficits [2]. Individuals with DS suffer from medical problems such as heart disorders and visual deficiencies [3]. Around one in 700 newborns is affected by the DS [4]. Tobacco consuming [6], obese [5], and older women bear a greater risk [6]. Diagnosis in early pregnancy and, for example, fetal biochemical and functional stimulation therapy is assumed to lead to an improved development of the child’s DS phenotype [7]. Current average life expectancy of people with DS is between 55 and 60 years, and Alzheimer disease is common development [8].

Parents influence their children’s genes in a twofold way, through direct heritage and the expression of their own genes. With decreasing dependency on the parents, individuals are more actively seeking environmental influences by their own that fit their genetic abilities [1]. Babies’ cognitive development starts with a sensorimotor stage according to Piaget’s theory, in which they respond with movement to stimuli of objects such as the sight of the face of a parent [9]. Young children’s behavior with DS in therapeutic sessions may look quite normal. Indeed, evidence shows that the difference in the development of motor skills for individuals with DS lies in its delay rather than its characteristic [10]. The most aggravating deficits over time from early childhood to school age and beyond are verbal weaknesses [2], while the social behavior of persons with DS can be extraordinarily bright [1].

There is a big variation in profiles of DS. More specifically, the mental retardation may be different across cognitive domains; for example, due to DS, children’s verbal working memory is comparatively less capable than the visual-spatial memory [11]. Standard intelligence tests predominantly measure abilities related to language and logical-mathematical thinking and are neglecting areas like musical and spatial capacities that are, according to Gardner and his multiple intelligence theory, part of a wider human spectrum of intelligence [12]. [1] is pointing to a so called ‘reaction range’ for intelligence that represents the possible variation of cognitive development. For mild cognitive disabilities, as defined to be represented by IQ scores of under 70 [1], ‘normality’ may be well within reach. The plasticity of neural and muscle tissues can be harnessed by therapeutic measures [13]. Children’s active desire to learn [9] can be used by a supportive social process of guided participation [1]. It is important to remember (especially in developed western societies) that traditional IQ tests have little to do with achievement other than in the academic space [14]. IQ and cognitive development is “a reflection of how we are brought up” [15].

References

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