Chapter 1 Notes: Developmental Psychology
The reason you will find so much research focused on childhood is that so many enormous and
fundamental changes are concentrated in this period of our lives. However, developmental
psychologists are concerned with the entire lifespan of human beings.
It is difficult to design an experiment I which all the potentially relevant extraneous variables
have been controlled for. It is also important to remember that numerous other developmental
processes are taking place at the same time.
Even if we show through experimentation that some variable can influence development, it does
not necessarily mean that it actually does influence normal development in the “real world”. In
fact, developmental change in a system may be the product of the simultaneous action of a
large number of variables.
Quasi-experiment: most commonly used research method in developmental psychology in
which subjects are grouped based on their existing levels of a variable, rather than attempting to
randomly assign subjects to different levels of a variable (Ex: sorting all three-year olds into one
However… when we use the Quasi-experiment, we are not randomly assigning subjects to
conditions and therefore cannot make the same kind of cause-and-effect interpretations of our
There are 2 kinds of questions that can be asked about development…
1) Descriptive or Normative Research: asks questions about how things normally
change from age to age – What is the individual capable of at any given age?
2) Analytic Research: asks about the processes and variables that are responsible for the
changes in abilities and needs from age to age. Why does change occur?
Longitudinal Design: Compare development at different ages by following the same group of
individuals over a period of time, and repeatedly describing or testing those individuals – a form
of within-subjects design
Advantages: Eliminates a lot of potential extraneous variables
Disadvantages: Time consuming and costly, subjects can be lost over time, subject to practise
effects, subject to cohort effects – developmental changes reflect experiences specific to
subjects of a particular cohort or generation (development is profoundly affected by social and
Dominant Traits: expressed if either parent contributes the genetic instructions for it (ex: brown
eyes, dark hair, dimples) Recessive Traits: only expressed if both parents contribute a genetic instruction for it (ex: blue
eyes, baldness, red hair).
The link between the genotype (genetic blueprint) and your phenotype (observable traits) is
indirect because each gene controls the production of a particular protein or enzyme that in
turn, regulates a biochemical sequence.
The Cascade Gene Model suggests that the SRY gene (located on the 23 chromosome) is
only one gene amongst many interacting genes that produce the sex of an individual, and that
both male and female factors contribute.
Androgen Insensitivity Syndrome: Individuals are