4PAHPDEV Psychology and Development Week 3
BSc Psychology Year 1 The Heritability of Individual Differences
THE HERITABILITY OF INDIVIDUAL
DIFFERENCES
BEHAVIOURAL GENETICS
• Behavioural genetics quantifies how genes and the environment interact to shape human
behavioural traits, focusing on individual differences
o This field studies the interplay between nature and nurture
• Research does not often find more than 50% of behavioural traits explained by genes, as the
environment is more responsible than genes for individual differences (Plomin et al., 2016)
• Behavioural geneticists examine connections between multiple behaviours rather than
isolating single genetic or environmental contributions
• Advances in gene identification enable precise study of developmental patterns, multivariate
relationships, and gene-environment interactions
• Psychologists agree social and environmental experiences significantly influence
development, though genetic inheritance imposes some limitations
GENE-ENVIRONMENT INTERPLAY
Range of Reaction
• The concept of range of reaction (Gottesman, 1963; Gottlieb, 2003; Plomin, 1995) suggests
heredity does not rigidly fix behaviour but set boundaries for a range of possible
developmental outcomes that may occur in response to different environments
o For example, giving a child a stimulating and enriched environment can enhance their
achievement, but their genotype will define the boundaries within which their
performance can fluctuate
• Strong canalization refers to an extremely narrow reaction range (Waddington, 1962, 1966)
o For example, a baby’s tendency to babble is strongly canalised, since it occurs
universally and so is largely unaffected by external influences (Lenneberg, 1967)
o Numeracy is less canalised since it can be modified by many physical, social and
educational experiences
1
, 4PAHPDEV Psychology and Development Week 3
BSc Psychology Year 1 The Heritability of Individual Differences
Bidirectional Influence
• Gottlieb (1991, 1992, 2007; Gottlieb & Lickliter, 2004) argues that genes play a less
deterministic role in shaping development
o Individual development consists of multiple levels where genes and environment
mutually influence one another, with events at each level impacting the others
• Genes can influence environmental experiences, which in turn influence genes
o This makes it hard to separate the factors involved, so most focus on understanding
how they work together rather than assigning responsibility to one (Rutter, 2006)
Critical Period
• Both the given development stage and environment determine the likelihood that a
genetically based trait or characteristic will be influenced by environmental forces
o For example, delaying a special diet for children with phenylketonuria can harm
intellectual functioning, while starting it at birth enables near-average scores
(Baumeister, 1967)
Misconceptions About Behavioural Genetics
Genes limit potential. Wrong. Genetic factors do affect potential, but that potential is also
affected by a child’s environment. If the environment changes, the potential changes too.
Strong genetic effects mean that the environment influences are not important. Although
genetic effects account for individual variability, the environment may nonetheless affect
changes in the expression of a characteristic across individuals.
Nature and nurture are separate. Both genes and environment are necessary for an individual to
develop: 'No genes, no organism; no environment, no organism' (Scarr & Weinberg, 1983)
Genetic influences diminish with age. Wrong. The relation between genes and ageing is highly
complex. Some hereditary characteristics are most evident in early stages of development; some
are more evident in later stages.
Genes regulate only static characteristics. Wrong. Genes affect developmental changes as
well. Deviations in the normally expected environment can upset the timetable for the child's
physical and psychological development, producing gross delay. However, the time at which
particular characteristics emerge and the sequence in which they appear are influenced by the
child's genetic inheritance.
2
BSc Psychology Year 1 The Heritability of Individual Differences
THE HERITABILITY OF INDIVIDUAL
DIFFERENCES
BEHAVIOURAL GENETICS
• Behavioural genetics quantifies how genes and the environment interact to shape human
behavioural traits, focusing on individual differences
o This field studies the interplay between nature and nurture
• Research does not often find more than 50% of behavioural traits explained by genes, as the
environment is more responsible than genes for individual differences (Plomin et al., 2016)
• Behavioural geneticists examine connections between multiple behaviours rather than
isolating single genetic or environmental contributions
• Advances in gene identification enable precise study of developmental patterns, multivariate
relationships, and gene-environment interactions
• Psychologists agree social and environmental experiences significantly influence
development, though genetic inheritance imposes some limitations
GENE-ENVIRONMENT INTERPLAY
Range of Reaction
• The concept of range of reaction (Gottesman, 1963; Gottlieb, 2003; Plomin, 1995) suggests
heredity does not rigidly fix behaviour but set boundaries for a range of possible
developmental outcomes that may occur in response to different environments
o For example, giving a child a stimulating and enriched environment can enhance their
achievement, but their genotype will define the boundaries within which their
performance can fluctuate
• Strong canalization refers to an extremely narrow reaction range (Waddington, 1962, 1966)
o For example, a baby’s tendency to babble is strongly canalised, since it occurs
universally and so is largely unaffected by external influences (Lenneberg, 1967)
o Numeracy is less canalised since it can be modified by many physical, social and
educational experiences
1
, 4PAHPDEV Psychology and Development Week 3
BSc Psychology Year 1 The Heritability of Individual Differences
Bidirectional Influence
• Gottlieb (1991, 1992, 2007; Gottlieb & Lickliter, 2004) argues that genes play a less
deterministic role in shaping development
o Individual development consists of multiple levels where genes and environment
mutually influence one another, with events at each level impacting the others
• Genes can influence environmental experiences, which in turn influence genes
o This makes it hard to separate the factors involved, so most focus on understanding
how they work together rather than assigning responsibility to one (Rutter, 2006)
Critical Period
• Both the given development stage and environment determine the likelihood that a
genetically based trait or characteristic will be influenced by environmental forces
o For example, delaying a special diet for children with phenylketonuria can harm
intellectual functioning, while starting it at birth enables near-average scores
(Baumeister, 1967)
Misconceptions About Behavioural Genetics
Genes limit potential. Wrong. Genetic factors do affect potential, but that potential is also
affected by a child’s environment. If the environment changes, the potential changes too.
Strong genetic effects mean that the environment influences are not important. Although
genetic effects account for individual variability, the environment may nonetheless affect
changes in the expression of a characteristic across individuals.
Nature and nurture are separate. Both genes and environment are necessary for an individual to
develop: 'No genes, no organism; no environment, no organism' (Scarr & Weinberg, 1983)
Genetic influences diminish with age. Wrong. The relation between genes and ageing is highly
complex. Some hereditary characteristics are most evident in early stages of development; some
are more evident in later stages.
Genes regulate only static characteristics. Wrong. Genes affect developmental changes as
well. Deviations in the normally expected environment can upset the timetable for the child's
physical and psychological development, producing gross delay. However, the time at which
particular characteristics emerge and the sequence in which they appear are influenced by the
child's genetic inheritance.
2
