The study involves three generations of subjects. Relatively little data have been collected on the original G1 parents of the main birth cohort, whereas much more extensive longitudinal data have been collected on the G2 birth cohort itself. Data have been collected on some of the G3 offspring of the birth cohort.
The birth cohort (G2)
The 1,795 male and female birth cohort was assessed on a wide range of psychophysiological, cognitive, temperamental, behavioural, nutritional, health and psychosocial measures when aged 3 years. Extensive autonomic assessments (skin conductance and heart rate) of arousal, orienting and fear conditioning were conducted.8
Cognitive functioning and intelligence were assessed using the Boehm Test of Basic Concepts.9
Inhibited and disinhibited temperament styles were assessed from observations of the children in the laboratory with their mother and other children,10
as well as fearlessness and stimulation seeking.11
Paediatricians conducted a physical assessment of all children to assess for the seven signs of malnutrition, while blood samples were taken to assess haemoglobin levels.12
At this time, birth record information was also coded from hospital records to assess birth complications.13
Exposure to the 1969 Hong Kong influenza epidemic was also retrospectively assessed in the G1 mothers when pregnant with their G2 offspring in the second and third trimesters of pregnancy.14
From age 3 to 8 years, 200 of the children (100 in the environmental enrichment group and 100 controls) were retested on autonomic functioning every year, using the same paradigm employed at age 3 years, to assess for developmental trajectories of basic information-processing ability, including orienting, habituation and classical conditioning.15
At age 8 years, 1,299 of the original children were rated by their teachers on a checklist for behaviour problems, including antisocial behaviour, aggression, hyperactivity and anxiety.16,17
Psychosocial and demographic data were collected, while height, weight and chest measurements were collected from school medical examinations.
At age 11 years, a major psychophysiological retest was conducted. In addition to repeating the autonomic data collected at age 3 years, additional data were collected on smooth-pursuit eye movements and also electroencephalogram (EEG) and event-related potentials, both at rest and during a continuous performance task.18
Cognitive functioning was assessed using the wechsler scale for children [Wechsler Intelligence Scale for Children (WISC)] and the trail-making test.19
Social workers visited the homes of the parents to collect detailed information on demographics, living conditions and siblings. During this visit parents completed the Child Behavior Checklist (CBCL),20
measuring childhood internalizing and externalizing behaviour problems.
At age 17 years, the sample was assessed on the Revised Behaviour Problem Checklist,21
assessing conduct disorder, socialized aggression, attention problems, motor excess, anxiety/withdrawal and psychotic behaviour, together with a measure of schizotypal personality.22
A computerized neuropsychological tests battery was also administered,23
including the continuous performance task,24
span of apprehension,25
mazes and reaction-time measures.
At age 23 years, assessments were made on self-report crime,3
depression using the Beck Depression Inventory,26
schizotypal personality using the schizotypal personality questionnaire (SPQ),27
alcohol use using the Michigan Alcohol Screening Test28
(MAST), head injury and handedness. All district courts on the islands were searched to track official crime records on the 1,795 participants.
At age 28 years, diagnostic interviews were conducted using SCID I and II (structured clinical interview for axis I and II DSM-IV disorders) to access all axis I and II disorders. Other measures included the stimulant and sedative effects of alcohol, child abuse, handedness and demographic information.
At age 35 years, the new intergenerational phase of the study on G3 (see below) also involved the original cohort of G2 parents. Parents were assessed on parenting skills (see below), daily hassles and uplifts, major life events, suicide ideation, spouse abuse, neighbourhood social cohesion, state and trait anxiety, impulsivity, stimulation seeking, positive and negative affect, a 7-day log of sleep and consumption of alcohol, caffeine, cigarettes and drugs, history of head injury, adult attention deficit hyperactivity disorder (ADHD), and adult attachment and happiness, both across the life-span and also in different social contexts.
At age 40 years, participants are currently engaged in another self-report test wave that repeats some of the negative outcome measures previously obtained, covering reactive and proactive aggression (reactive–proactive questionnaire; RPQ),29
schizotypal personality (SPQ-B),30
psychopathic personality (PSI),31
self-report crime, spouse and child abuse (conflict tactics scale; CTS),32
adult ADHD, alcohol use (Alcohol Use Disorders Scale; AUDIT),33
state-trait anxiety (STAI)34
and depression (Beck Depression Inventory, Beck).26
In addition, positive psychology measures are being taken in order to both assess early life factors that shape positive outcome, and also to assess how they may act as protective factors against negative adult outcome. Measures include achievement, interest and effort,35
life satisfaction, happiness, curiosity and exploration, hope, inspiration, personal growth and income. Basic demographic measures covering income and occupation are also derived.
Offspring of the birth cohort (G3)
The new G3 offspring of the original cohort have been assessed at age 3–4 years, the same age that their parents had been originally tested in the same laboratory ~30 years earlier. The same autonomic arousal, orienting and habituation measures that had been originally assessed on the parents were included, together with new measures of vagal tone, EEG, event-related potentials and startle blink. New psychophysiological paradigms were added to induce emotions of empathy, fear, reward expectancy and frustration. Comprehensive behavioural test batteries in the laboratory setting included seven measures of inhibitory control and rule-breaking behaviour.36,37
Observational measures were also made of the children interacting with their caregiver in 10 different contexts to derive measures of parenting skills and also children's reactivity to parenting.38,39
Parents also completed measures of child behaviour problems [Child Behavior Checklist(CBC)], 10 dimensions of conscience,40
15 dimensions of temperament,41
parenting hassles and child-rearing agreements.42
Intelligence was assessed using the (Wechsler Preschool and Primary Scale of Intelligence – Revised). Research assistants visited the mother and child at their homes and completed the Home Observation for Measurement of the Environment, which assesses eight dimensions of the quality of the child's home environment,43
together with detailed demographic and psychosocial adversity measures.
At age 7–11 years, another G3 test phase was introduced, which included both older G3 children of the original G2 birth cohort, as well as a retest of some of the G3 children already assessed at age 3 years. Psychophysiological testing was repeated. Parents also completed a demographic interview. Neuropsychological testing was conducted, covering the areas of executive functioning, memory, verbal fluency, colour trails and visuo-spatial functions. Intelligence was also assessed using the WISC-III. Parents again completed the CBC, together with the RPQ.29