Developmental Psychology: Intrauterine, Infancy & Childhood
• A zygote is the fertilized egg that contains genetic material from both the egg and the
sperm and its brief lifetime is called the germinal stage. Contrary to what many
people think, fertilization does not happen right away. It typically happens 1 to 2 days
after intercourse, but can happen as many as 5 days later. The genetic sex of the
individual is determined at the time of fertilization; fertilized eggs containing an XY
sex chromosome complement are genetic males, whereas those containing an XX sex
chromosome complement are genetic females.
By the time an infant is born, its body contains trillions of cells, each of which came from
the original zygote. During the germinal stage, the zygote migrates down the fallopian
tube and implants itself in the wall of the uterus. Half of them don't complete it,
because they are defective or implant themselves in an inhospitable part of the uterus.
Male zygotes are especially unlikely to make the journey. In an ectopic pregnancy, the
egg attaches itself somewhere outside the uterus — usually to the inside of a fallopian
tube.
This is the prenatal stage: of the 200 million sperm that travel to the womb, only 200
enter the correct fallopian tube, getting close enough to an egg to release digestive
enzymes that erode egg's protective outer layer, the egg will then release a chemical
that seals the protective coating. 12 hours later, the egg will merge with the nuclei of
the sperm, creating a zygote, containing the 46 (23m + 23f) chromosomes of both
the egg and the sperm.
The embryonic stage begins when the zygote successfully implants itself within the
uterine wall. This stage begins at the end of the second week and lasts until about the
8th week. Cells continue to divide and they begin to differentiate.
This occurs because of Hox genes, a subset of homeobox genes, are a group of related
genes that specify regions of the body plan of an embryo along the head-tail axis of
animals. Hox proteins encode and specify the characteristics of 'position', ensuring that
the correct structures form in the correct places of the body. If it is a male embryo, it
begins to produce testosterone.
The fetal stage lasts from 9 weeks up until birth. In neurology, what is most
important is myelination, the formation of a fatty sheath around the axons of a
neuron, both shielding the axons from each other, and speeding up neural
transmission.
A foetus has a skeleton and muscles, and is capable of movement.
A neonate (newborn) human brain is only 25% of its adult size. Why? One of our
species greatest talents is to adapt to a wide range of novel environments, and
requires neuroplasticity--the alteration of synaptic connections--and neurogenesis--the creation of new neurons from stem cells.
As the embryonic brain continues to grow, each subdivision folds onto the next
one and begins to form the structures easily visible in an adult brain.
Ontogeny: how a brain develops within a given individual.
Phylogeny: how a brain develops within a particular species.
The rudimentary brain areas found in simple invertebrates eventually evolved
into our complex brain structures, all from that original neural tube.
In all vertebrates, the central nervous system is organized into a hierarchy, the
top of which is the forebrain.
In higher vertebrates, the forebrain evolves in two different patterns; reptiles
and birds have almost no cerebral cortex, while mammals have a highly
developed cerebral cortex, with multiple specialized areas.
The human forebrain shows substantial refinement such as self-awareness,
language use, abstract reasoning and imagination.
The Role of Epigenetics
Epigenetics: environmental influences that determine whether or not a gene gets
expressed, the DNA sequences that constitute the gene are not altered.
Epigenetic markers: DNA methylation which switches genes off;
Histone methylation which switches genes on and off. Neither alters the underlying DNA.
Genes are sections on a strand of DNA, organized into large threads
(chromosomes) which form into a double helix.
The DNA is our chromosomes produces protein molecules through the action of
messenger RNA, which communicates a copy of the DNA code to cells to produce
proteins.
Sharing traits: the most genetically related people are monozygotic twins.
Dizygotic twins develop from two separate fertilized eggs and share 50% of their
genes.
Twin studies are an important part of developmental psychology; usually there is
a comparison of monozygotic twins raised together, and apart, to study the
interaction of genetics and environment.
Discovering that monozygotic twins share a higher percentage of a specific trait
suggests a genetic influence.
The likelihood of a dizygotic twin developing schizophrenia is 27%; that for
monozygotic twins is 50%.
Genetics can contribute to the development, likelihood, or onset of a variety of
traits.
Epigenetic markers left by DNA methylation and histone methylation play a role in
learning and memory. In Psy 121.3, we will focus on DNA methylation.
Studies of nurses working in high or low stress environments found differences in DNA
methylation in the two groups. (Alasaari et al., 2012)
Meaney Epigenetic Studies
Several studies have linked epigenetic changes with responses to stress. (Zhang &
Meaney, 2010).
DNA and histone methylation also play a key role in longlasting effects of early
experiences in both rats and humans. These effects are accompanied by
physiological changes.
High LG (licking & grooming) mother rat: increased serotonin in the hippocampus;
decrease in DNA methylation (turning genes off) of the glucocorticoid receptor gene
related to stress; greater expression of the gene. Result? A greater ability to respond
calmly to stress. High LG pups grow to be 'chilled out' adults with better regulated
stress response.
Low LG (licking & grooming) mother rat: decreased serotonin in the hippocampus;
increase in DNA methylation of glucocorticoid receptor gene (related to stress);
reduced expression of the gene. Low LG pups grow into adults with less ability to
respond calmly to stress.
The human equivalent of high LG is probably loving and attentive parenting.
McGowan (2009) reports a role for epigenetics in the persisting effects of childhood
abuse on adult men. Kundakovic et al. 2015 report a connection between this abuse
and later depression, schizophrenia, and posttraumatic stress disorder.
Prenatal Environment & Teratogens
Placenta physically links the bloodstream of the mother to that of the embryo.
Children of mothers who receive insufficient nutrition enter the world with both
physical and psychological problems, the first being low birth weight.
Rifkin (1994) reported that a birth weight of less than 2500 g was significantly
more common in patients with schizophrenia than in those with affective
psychosis.
Schizophrenic patients as a group had significantly lower mean birth
weight, a finding which was particularly marked after controlling for
sociodemographic confounders. In Psy 121.3 we call these 'hidden' or 'latent' variables.
Antisocial personality disorder is also more likely. Boyle (2011) reports an increase
in psychopathology in young adults born with extremely low birth weight.
Teratogens are agents that impair prenatal development, such as alcohol, drugs
and viruses. Tobacco is another, both first and secondhand smoke.
The embryo is more vulnerable to teratogens than the foetus, but the central
nervous system is at risk until birth.
A foetus cannot see, but it can hear, preferring the sound of it's mother's voice
above all else; newborns will cry with the inflections of their mother's language.
Infancy
Newborns can see detail at 6.1 metres; they are quite visually responsive for
stimuli 20 to 50 cm away, just the distance between the baby's and the mother's
face. Newborns habituate to visual stimuli, losing interest in sameness, and quickly
noticing novelty. (Slater, Morrison & Somers, 1988).
Newborns are especially sensitive to social stimuli. They have been shown to mimic
facial expressions in the first hour of their life (Reissland, 1988) and mimic speech
sounds as early as 12 weeks (Kuhl & Meltzoff, 1996).
Infant Motor Development
Infant motor development is the emergence of the ability to execute physical
actions.
Infants are born with a small set of reflexes, specific patterns of motor response
that are triggered by specific patterns of sensory stimulation. Rooting and suckling
are the most prominent.
Most reflexes disappear within the first few months as infants learn to execute
more sophisticated motor behaviours. An involuntary walking reflex can become
voluntary walking (Zelazo, 1983).
Motor Development
Cephalocaudal rule: the 'top to bottom' rule the describes the tendency for motor
skills to emerge in sequence from the head to the toe.
Proximodistal rule: the 'inside to outside' rule that describes the tendency for
motor skills to emerge in sequence from the centre to the periphery. Infants learn
to control their torsos before their arms and legs; this is the reason that they have to
cry.
Piaget's Four Stages of Cognitive Development
Schemas are an infant's theories about the way the world should work; here we
are applying the concept of 'phenomenological intentionality'.
Assimiliation: infants successfully apply their theories to novel situations.
Accomodation: infants' theories do not map out reality; infants must revise.
Object permanence: the belief that objects continue to exist even when they are
not visible. Infants demonstrate this belief much earlier than Piaget realized
(Shinskey & Munakata, 2005).
Childhood Cognition
Preoperational stage: begins at about 18 to 24 months and lasts until 11 to 14
years.
Preoperational children do not fully grasp the fact that they have minds and that
these minds contains mental representations of the world. They do not yet
distinguish between subjective and objective, illusion and reality.
Egocentrism is the failure to understand that the world appears differently to
different people.
However, young children can understand another's desires (emotions) much better than
another's beliefs (Repacholi & Gopnik, 1997).
Conservation: the notion that quantitative properties of an object are invariant
despite changes in the objects appearance.
Concrete operational stage: begins about 6 years and ends at about 11 years,
during which the child learns how various actions of 'operations' can affect or
tranform 'concrete' objects.
Formal operational stage: for Piaget, the final stage of cognitive development that
begins at the age of 11. Abstract reasoning and hypothesis testing.
Why Can't We All Be Jet Fighter Pilots?
Let us apply what we have learned about the cerebellum and cognition to Piaget's Formal Operational stage. A jet fighter pilots needs to be able to perform an Euler rotation (roll, pitch, yaw aka rudder) intuitively at high speeds. For geometry buffs, this means calculating a 3d rotation and knowing the outcome. This advanced cognitive and motor skill has to be selected out of a population, not everyone can do this.
What is ASD or Autism Spectrum Disorder?
Core Characteristics
Social Communication & Interaction: Difficulty with back-and-forth conversation, understanding nonverbal cues (like eye contact, gestures), and forming relationships.
Restricted & Repetitive Behaviors: Intense focus on specific interests, need for sameness, rigid routines, and repetitive physical movements (e.g., hand-flapping).
Sensory Differences: Unusual sensitivity to sounds, lights, textures, or other sensory input, or a lack thereof.
Genetic Basis of Autism Spectrum Disorder
Autism Spectrum Disorder (ASD) involves hundreds of genes, with prominent ones often affecting synaptic function (like SHANK3, NRXN1, CNTNAP2, NLGNs) or brain development, but it's usually a complex interplay of many genes and environmental factors, not a single gene. Key implicated genes include DDX53, FGF13) and those related to neurotransmission, such as SCN1A, MECP2, and SLC6A11. Mutations in genes like CHD8, SHANK3, ADNP, and SYNGAP1 are linked to syndromic (for example. Savant Syndrome) forms of autism, while common variations contribute to broader risk.
Key Gene Categories & Examples
Synaptic Genes: Crucial for neuron communication. Mutations in SHANK3, NRXN1, CNTNAP2, and NLGNs are frequently found.
Chromosomal Regions: Deletions or duChromosomal Regions:plications in regions like 16p11.2, 15q13.3, and 22q13 are associated with ASD.
X-Chromosome Genes: Recent studies highlight genes like DDX53, FGF13, HDAC8, and PCDH11X.
Transcription Factors: Genes like FOXP2 are involved in speech and language development, with mutations linked to ASD features. Transcription factors are proteins that turns genes 'on' or 'off'.
Syndromic Genes: Rare mutations in genes like ADNP, ARID1B, CHD2, CHD8, DYRK1A, POGZ, and SYNGAP1 cause ASD as part of broader syndromes.
Neurotransmitter-Related Genes: SCN1A, MECP2, and SLC6A11 affect GABA and glutamate signaling.
Why So Many Genes?
Polygenic Risk: A combination of common genetic variations, inherited from both parents, increases risk.
Rare Mutations: De novo (new) or inherited rare mutations in single genes can have a significant impact.
Gene-Environment Interaction: Environmental factors, like maternal health or prenatal exposures, interact with genetic predispositions. The most important environment for determining the extent of ASD is the intrauterine.
What Brain Areas are Most Affected by Autism? Let's Look at the Cerebellum
https://www.youtube.com/watch?v=Ct6a6z_roiA
In individuals with autism spectrum disorder (ASD), structural and functional abnormalities in specific cerebellar regions are consistently linked to core symptoms and associated cognitive deficits.
Review the Purkinje cell; many studies of autopsies of autistic brains have shown a decrease of 50% to 90% of Purkinje cells in the cerebellum.
Savant Syndrome, an aspect of ASD
Savant syndrome involves atypical brain structure and connectivity, often characterized by right hemisphere dominance and left hemisphere dysfunction, particularly in the temporal lobe, leading to enhanced detail-focused skills and memory.
Key Brain & Connectivity Findings:
Right Hemisphere Hyperactivity: Increased volume and connectivity in the right hemisphere, especially the amygdala, hippocampus, frontal, and occipital lobes, supports enhanced memory and perceptual processing.
Left Hemisphere Dysfunction: Often involves damage or reduced function in the left anterior temporal lobe, which normally handles semantic memory, leading to a focus on literal details rather than context.
Corpus Callosum Anomalies: Some savants lack a corpus callosum (connecting the hemispheres) or have a malformed one, which, surprisingly, may force the hemispheres to develop unique communication pathways or compensate for each other.
Altered Connectivity: Studies suggest altered brain networks, with increased local connectivity in the right hemisphere and reduced communication between hemispheres, contributing to hyper-focused skills
Autism & Theory of Mind
Understanding that human behavior is guided by mental
representations. Although children with autism are typically normal on most intellectual
dimensions, they have difficulty understanding the inner lives of other people.
Autistic children have difficulty that others can hold false beliefs; they struggle to
understand belief based emotions such as embarassment and shame.
The age at which children acquire a theory of mind is influenced by: the number of
siblings; frequency of pretend play; imaginary companions; socioeconomic status of
the family.
Language skills are the most important factor in determining a child's theory of
mind, especially if they are exposed to psychological words like want, think, know
and sad.
Language with complex grammatical structures, whose subjects are thoughts and
feelings are an important tool for helping children make sense of their own and
others' minds.
Piaget remixed: modern psychologists see development as more fluid and
continuous, more mature behaviours will flucuate with less.
Joint attention allows a children to learn from others. When a 12month old infant
interacts with an adult who then looks at an object, the infant will typically look at
the same object, but only when the adults eyes are opened.
Early on, infants mimic adult's intentions, rather than their actions (There's
intentionality applied, again).
Infants will stop and use another person's reactions to determine if their action is
safe or not.
Infants use social information in a very sophisticated way. When their senses
provide unambiguous information about their world, they will ignore what their
caretakers tell them. They will accept parental advice when they are unsure.
(Tamis LeMonda et al., 2008)
Harlow's monkeys
Harry Harlow (1965) discovered that infant rhesus monkeys who were warm, safe and
well fed, but not allowed to any social contact for the first six months of their live
developed behavioural abnormalities. Eg: they compulsively rocked back and forth
while biting themselves.
In experiments, Harlow's monkeys preferred the comfort and warmth of a cloth
mother to the wire mother, even though the later was associated with food.
The Four Main Attachment Styles
Secure: Comfortable with intimacy and independence, trusting, good communication, balanced approach.
Anxious-Preoccupied: Craves closeness but fears abandonment; can seem "clingy," needs reassurance, worries about partner's love.
Dismissive-Avoidant: Values independence highly, uncomfortable with closeness, suppresses feelings, might seem distant.
Fearful-Avoidant (Disorganized): Wants intimacy but fears it, inconsistent behavior, struggles with trust, often stems from trauma.
Origins & Impact
Childhood Experiences: These styles form from interactions with primary caregivers; consistent, reliable care fosters security, while inconsistent or neglectful care can lead to insecure styles.
Adult Relationships: They shape how you behave in romantic partnerships, friendships, and family dynamics, affecting trust, emotional expression, and conflict resolution.
Moral judgments may be the consequences and not the causes of emotional
reactions (Haidt, 2001). This is the moral intuitional perspective.
Why? Because watching someone suffer activates the same brain areas that are
activated when we suffer. (Carr et al. 2003)
Our brains respond to other's expressions of suffering by creating within us the
experience of suffering. (de Waal, 2012).
Even small children consider it wrong when someone hurts someone else,
especially if that person is similar to the child. (Hamlin et al., 2013).