Developmental psychology - summary of chapter 21 of an Introduction to Developmental psychology by A. Slater and G. Bremner (third edition)

Developmental psychology
Chapter 21
Atypical development

Two ways in which development can be atypical

• Development can be exceptionally advanced or exceptionally low. The extremes of individual differences in development
• Development may be qualitatively different from typical development

Williams syndrome: a rare neurodevelopmental disorder caused by deletion of about 26 genes from the long arm of chromosome 7.

What is atypical development?

Considering whether a child development is

• Delayed: a delayed but normal path of development
• Different: a qualitatively different path of development

Quantifying delay

• Looking at achievements in a time frame
• Looking at the extent to which individual children perform relative to a level expected for their chronological age on standardized tests.
• The size of difference between the child’s score and the norms established for the population

Types of delay

• A particular aspect of development is delayed tells the researchers little about what underlies the delay.
• The predominantly descriptive use of the term is relatively unhelpful, what is needed is an explanatory account of delay that identifies the various possible causes of delay in specific domains.

Assessment of delay is not confined exclusively to norms for atypical development. Standardized assessment scales have been designed for use with specific exceptional populations.

Why study atypical development?

The study of atypically developing children provides a profile of the main behaviors associated with a condition withing the context of development across the human lifespan.
This profile has the potential to generate a new knowledge base from which to design and deliver interventions.
Unfortunately, in the context of a relatively young field, there remains insufficient description of the atypical trajectories associated with particular disorders to warrant a sufficiently robust evidence base to inform the design and delivery of interventions fit-for-purpose.
Studying development that is considered atypical can inform us about development that is typical and vice versa.

Methodological approaches used in the study of atypical development

• Make a comparison between the performance of the atypical sample and the performance of the relevant control group sample.
• The false belief task is frequently used to assess atypically developing children’s understanding of mental states.
• Typically, there is comparison between one group and one or more control groups. A common practice is to compare a clinical group with two control groups, both of which are typically developing. One control of chronological age and one of mental age.
  The matching across groups could potentially be achieved at the level of the individual or the level of the group.
  • If the clinical group underperform compared wit the chronological age group, the individuals demonstrate delay
  • If the clinical groups underperform compared with the mental age group, the clinical group is showing qualitatively different behavior.

Autism spectrum disorder: a spectrum of psychological conditions characterized by widespread abnormalities of social interactions and communication, as well as severely restricted interest and highly repetitive behavior.

Congenital blind: the condition of being born unable to see or with severe visual impairment.

Impact of scientific discovery and technological innovation on the study of pathways in atypical development

Three major developments having an impact on our understanding of pathways in atypical development:

• Impacts as we enter the era of genomics. And the legacy of the discoveries from the Human Genome Project.
  The Human Genome Project: one of the biggest research projects in the world. The research found that the number of genes was fewer than previously thought and was a strong indicator that there was more to specifying humanity than action of individual genes in isolation.
• The state of the art techniques in brain imaging are enabling researchers insights into both the location and function of neural substrates relevant to atypical pathways.
• Increasingly widespread of eye-tracking technology by human development

The impact of the human genome project on the study of atypical development

The small number of genes supports the notion that we are not had wired.
The notion that one gene leads to one protein and perhaps one disease is false.

Information contained in the separate genes in thought to ‘mingle’ in complex ways, resulting in a transformation of genetic information.
It seems that multitude of pathways are possible between genotype and expression.

Chromosomal structural abnormalities: an atypical number of chromosomes or a structural abnormality in one or more chromosomes.

Due this type of activity, it is likely to be growing emphasis on the distinction between typical and atypical genetic mechanisms.
Risks associated

• Genetic diversity is not valued

Genetic diversity: the total number of genetic characteristics in the genetic make-up of a species.

Amniocentesis: a medical procedure used in prenatal diagnoses of chromosonical abnormalities and foetal infections, in which a small amount of amniotic fluid, which contains foetal tissues, is extracted from the amnion or amniotic sac surrounding a developing foetus, and the foetal DNA is examined for genetic abnormalities.

How advances in brain imaging are aiding understanding of pathways in atypical development

Neuroimagning tools aid localization of brain activity that, in turn, enable developmental psychologists to understand more about the pathways associated with atypical development.
Typically used with children:

• PET
• Event Related Potential (ERP)
  ERP has informed our understanding of atypical pathways were attentional development is at risk.
• Magnetoencephalograpthy (MEG)

Attention deficit hyperactivity disorder (ADHD)
Abnormalities in aspects of electrical activity in the frontal cortex.

Use of eye-tracking methodology in studies of atypical development

Allows precise measures of visual behavior.
It serves to capture attention with no overt task demands or explicit language requirements.
The researcher is able to exert control over the choice of scenes or stimuli to who participants

Saccades: eye movements in which the fast movement of the eye functions to shift fixation to an object of interest, so that its image is projected to the fovea.
Having control of eye movement allows humans to make saccades to suddenly appearing targets and to suppress such attentional shifts when it would distract from the task at hand.

Understanding atypical pathways

Atypical conditions of childhood can be characterized according to the type of causal pathways involved.

Williams syndrome

An extremely rare condition.
Studies lack generalizatabilty. Data sets are typically cross-sectional and a huge substatial age band (sometimes the order of 10-20 years).

Frequently, developmental scientists characterize Williams syndrome in terms of making a differentiation between language and cognitive domains.

• Cognition is atypical
  • Low non-verbal IQ
  • Difficulties in planning, problem solving and spatial cognition
• Language is spared
  • Highly sociable and communicative.
  • Language pragmatics is impaired (the competence of speakers to communicate in socially appropriate ways)

Specific language impairment (SLI): a developmental language disorder that can affect both production and comprehension and that is unrelated to other atypicalities in development.
When children with Williams syndrome where compared with children with SLI, there was a difference in they ability to use pragmatics.
Difficulties for children with Williams syndrome:

• They speech was overly dependent on the adult’s leads and contributions
• Leading the conversation forwards reflected in inability to add new information and respond to requests for new information.

These issues did not affect the children with SLI.

Levels of cognitive functioning appear to interfere with social and pragmatic aspects of communication.
Language skills cannot develop independently from cognitive abilities.

The social phenotype varies across cultures.

Autistic spectrum

Autism is known to be particularly hetrogeneous in terms of how it manifests itself.
Prevalence: 1 in 100
The core diagnostic features are currently defined at the level of behavior. Currently, there are no entirely reliable biological indicators such as brain abnormalities that can diagnose autism.
Post-mortems using PET or MRI reveal evidence of cerebellar deficits, and some studies report a genetic disposition.

DSM-V states impairments in social interaction, impairments in communication and repetitive behavior within a narrow set of interests.

Advent of eye-tracking technology is providing new insights into the nature of the impairments in social interaction as indicated by visual behavior.

• Atypical eye contact

Six major subgroups on the autistic spectrum. The subgroups are differentiated by cognitive ability level as measured by IQ and the extend to which there has been any delay in learning to talk.

• Asperger
• High-functioning autism
• Medium-functioning autism
• Low-functioning autism
• Atypical autism
• Pervasive developmental disorder

Explaining autism

Three main theories

• Theory of mind hypotheses
  The view that people with autism have difficulties in understanding that others have thoughts and beliefs
• Executive function hypotheses
  The view that autism is due a deficit in executive function
• Central coherence hypotheses
  The view that autism is due to lack of central coherence, which is reflected in the tendency to process information piecemeal rather than to integrate it.

Attention deficit hyperactivity disorder (ADHD)

Relative to typically developing children, those diagnosed with ADHD are excessively hyperactive or impulsive and inattentive.
In the classroom, they show considerable difficulties in maintaining visual attention and are frequently involved in ‘off task’ behavior.

The symptoms of ADHD are known to manifest across the lifespan and frequently co-occur with conduct disorder, and other behavioral disorders.

Cause

hypotheses:

• A core deficit in inhibitory control
• but, doubtable
• Multiple developmental pathways in ADHD
  Not only do a number of symptoms have to be explained by the model, but also there appear to be a cluster of related clinical features to be explained.
  A dual pathway hypotheses
  Different pathways that are both associated with executive function.
  More cognitively oriented aspects of executive function are associated with dorsolateral prefrontal cortex
  More affective aspects are handled by the orbital and medial prefrontal cortex.

Impact of the absence of a sensory input on developmental pathways

Ordinarily, the development of children with visual impairment would not characteristically be classed as disordered.
It is important to expand:

• Certain forms of visual impairment are caused by genetic abnormalities.
• It is certainly that sensory impairment children have atypical experience.
• A certain proportion of children who are sensory impaired due to congenital blindness also show behavioral symptoms of autism.
• Some accounts of atypical development assign vision a major driving role in, for example, early communicative development in the first year.

Once congenitally blind infants have learned to understand language and to speak, they have greater access to the environment through hearing the speech of others related to what is going on around them and in using their own language to elicit information from others about what is going on.

By 6 months of age, blind infants are able to establish a rapport with their caregivers.
Non-visual perceptual information is sufficient for establishing exchanges between blind infants and their parents.
Typically, interactions revolve around rhymes and touching routines.
Blind infant’s hands are an important source of information about affective states.
In contrast to sighted infants, person-person-object style interactions were not established in a reliable way until 21 months.

Established joint attention is comprising as sequence of four behaviors

• An initiating partner makes a bid for attention to a particular object or event
• The recipient makes an appropriate behavioral response
• The initiator follows with a response that indicates that the initiator is aware of the recipient’s attention
• The dyad focus visually on the object/event an attentionality engage one another and the object through

Blind infants touch

Children with a dual sensory impairment

Around 50 per cent of children who are registered blind have other disabilities.
For those children it is vital to encourage independence across all areas of development, especially in communication and in mobility.

Environmental risk factors: the case of emotional disturbance

Some forms of atypical development environmental input is likely to be at least a major contributory factor.

Bronfenbrenner’s ecological model
An influential model that places individual human development into the wider context of interaction with the immediate environment, as well as the larger context.
The absence or atypically of experiences that may influence the path of individual development.
Five levels:

• Microsystem:
  The individual child, their characteristics and the settings where interpersonal relationships relevant at different points in the lifespan take place.
• Mesosystem:
  The relation between different microsystems
• Exosystem:
  The variety of influences like the mass media, the neighbors and family friends
• Macrosystem:
  The cultural level of influence
• Chronosystem:
  The sociocultural events over the life course