1.1.4 Sensitive & Critical Periods

Psychological development

The lifelong process of emotional, cognitive and social change influenced by both hereditary and environmental factors

Hereditary–environment interaction

The combined influence of genetic factors (nature) and life experiences (nurture) on development

Biopsychosocial approach

A model that explains behaviour and mental wellbeing through the interaction of biological, psychological and social factors

Maturation

Biologically programmed growth that follows a fixed sequence and underlies all areas of development

Neural plasticity

The brain’s capacity to change its physical structure by forming, strengthening or weakening neural connections in response to experience

Critical period

A narrow, rigid window of development during which a specific skill must be acquired; deprivation at this time can cause permanent deficits

Sensitive period

A span in development when an individual is particularly receptive to certain experiences; learning is easiest then but still possible later

Language acquisition (critical period)

The optimal window—roughly the first 3-5 years—during which exposure to language is essential for full mastery of native speech

Genie Wiley

A case study of extreme isolation from 20 months to 13.5 years that highlighted the importance of sensitive periods for language learning

Developmental milestone

A notable skill or ability reached at a predictable age range, such as walking or first words

Vulnerability to deprivation

The heightened risk of lasting deficits when crucial environmental experiences are absent during a critical period

Sensitive vs. critical periods

Critical periods begin and end abruptly; skills must be learned then. Sensitive periods are broader and gradual; learning is easiest but still feasible later

First-language window

The early childhood interval when exposure to spoken language is required for normal grammatical and phonological development

Early-childhood brain plasticity

The high adaptability of a young child’s brain, allowing rapid formation of neural circuits in response to experience

Developmental 'map'

The genetically determined sequence that guides brain and bodily maturation

‘You can’t teach an old dog new tricks’

A saying challenged by brain plasticity research, showing humans can learn throughout life, though learning is often easier in sensitive periods

Environmental enrichment

Experiences that strengthen neural connections and foster development during sensitive or critical periods

Environmental deprivation

The absence of necessary experiences that can hinder development, particularly harmful during critical periods