12. Single System Research Design
This section introduces ‘single-system research designs’, sometime referred to as single-case or single-subject research designs (NB: Not to be confused with a case study). They involve key research strategies in behaviour analysis where the fundamental research agenda involves searching for functional relations between dependent and independent variables. A system in this context can be the behavioural repertoire of an individual person, a family, or a community. For example, if you want to know how independent variables in the environment (e.g., in clinical, educational, sport, autism settings) affect a particular behaviour, you monitor that behaviour before these interventions are introduced, then you continue to monitor the behaviour while they are in place, and finally you check how the behaviour change is maintained after the environmental changes have been removed.
We are talking here about ‘intra-’ rather than ‘inter-systemic’ changes. In other words, the focus is not on comparing one individual with another, but rather on comparing the same behaviour of one individual (system) before, during and after independent variables are systematically introduced.
‘... experiments to evaluate treatment effects involve directly observing and measuring one or more specific behaviors of an individual repeatedly for a period of time while a particular treatment is not in place (the control or baseline condition), and while it is (the experimental or treatment condition). Events other than the treatment that might affect the target behavior(s) are eliminated (controlled) as much as possible.’ (Green, 2008, p.74. In O'Brien, Dennis M., et al. Autism in Pennsylvania: What Lies Ahead? [Harrisburg, Pa.]: Pennsylvania House of Representatives).
This approach is firmly anchored in the scientific method that does not rely on inferential statistics. Students in Psychology classes seldom get taught how the scientific method can be used in this way. They come to study Psychology because they have an interest in working with people and they end up being taught exclusively about population statistics. In fact, they also get taught that any other approach to the scientific method other than comparing groups of people using inferential statistics is to be regarded as a ‘quasi’ experimental method, a method that only looks like science in action (Movie 12.1). Bombarded by this indoctrination, they end up with virtually no skills appropriate to the various needs of monitoring the behavioural stream of an individual in clinical or educational settings (Movie 12.2).
No one is ‘normal’. Everybody is made up of a multitude of individual characteristics. If you take an average of each of them (height, shoe size, length of fingers etc), you won’t find any individual who is average in all respects. This is known as the ‘jaggedness principle’.
In the 1940s the Jaggedness Principle forced the US Air Force to refit fighter planes with adjustable seats and other fixtures. The cockpits were originally designed around the average range of 10 body measurements taken from a population of 4,063 pilots. But because no single pilot met all those criteria, they ended up with a seat which actually didn’t fit anybody. (http://qi.com/infocloud/normal)
Here is a second one:
In 2011 the Australian Bureau of Statistics used the national census to find the average Australian. They announced that she is a 37-year-old woman with a son and a daughter aged six and nine. She is 162 cms (5’4”) tall, and weighs 71.1 kgs (11st). She lives in a three-bedroom house, has about $200,000 still to pay on her mortgage and her family originally came from the UK. However, when they checked this description against the census data they couldn’t find a single person in the whole country that fits that description.
(http://qi.com/infocloud/normal)
Finally, the third one:
The average length of human gestation is 280 days, or 40 weeks, from the first day of the woman's last menstrual period. The medical term for the due-date is Estimated Date of Confinement (EDC). However, only about 4% per cent of women actually give birth on their EDC.