Poster #119 - Is Nomothetic Psychology Dead? The Case for an Idiographic Approach

• In Event: 1-115 - Poster Session 03
  In Poster Session: PS 03 Section - Methods, History, Theory

Integrative Statement

The goal of academic psychology is to understand, explain, and predict behaviour. Over the last 150 years developmental science has produced many theories and bodies of knowledge that are important, interesting, and applicable to public policy. However, recent controversies have shaken the discipline. Although all-encompassing explanations of human behaviour are compelling, they may be the exception. In this paper I argue for an idiographic psychology. Three lines of evidence form the basis of this thesis.

First, across the sciences, recent years have seen a crisis in confidence. For psychology, the crisis was dramatically exposed in the report that only 36% of 100 studies published in three top journals in 2008 were successfully replicated (Open Science Collaboration, 2015). In addition, the average effect size of the replication studies was r = 0.197, whereas for the original studies it was more than double at 0.403. This crisis has generated interpretations of publication and/or experimenter bias (e.g., Giner-Sorolla, 2012). Perhaps we were wrong to think that studies should always replicate. Instead of “successful” experiments indicating the causal pathway, perhaps experiments demonstrate a causal pathway -- at a particular time, in a particular context, with a particular sample. It may not be realistic to expect many universal laws of human behaviour. Indeed, the replication crisis clearly demonstrates that a particular theoretical principle may “work” in some situations and not others, or more crucially, for some people and not others.

Second, molecular genetics has not delivered on the promise of specifying the many genes responsible for complex behaviours. In combination with environmental factors, it then becomes more and more evident that simple main effects of genes will be few and far between. I argue that this “missing heritability” indicates that complex gene-gene, and gene-environment interactions – none necessary or sufficient – are the most frequent explanatory mechanisms. Each person’s individual genome will hold idiosyncratic explanations for human behaviour.

Finally, an assessment of my own field, developmental psychology as informed by behavioural genetics, yields a shared environment paradox. On the one hand, behavioural geneticists insist that the shared (family) environment plays little to no role in human development (Plomin et al., 2016; Scarr, 1992). On the other hand, socialisation research documents robust prediction from a variety of shared environmental factors to important developmental outcomes. How can both of these statements be true? I unpack the shared environment paradox by highlighting that identical family environments can affect children, even within the same family, in very different ways. I argue that idiographic pathways are the essence of meaningful human psychology.

Perhaps as a result of evolutionary pressures, people’s responses to environmental stimuli are varied and replete with complex moderation effects. Moving beyond effect sizes, our language should indicate the extent to which links are universal. Idiosyncratic pathways are the essence of meaningful human psychology and not a measure of error, or a failure to account for variance. While traditional quantitative approaches remain crucial for informing public policy, alternate methodologies may be more useful for discerning meaning.

Author

• Alison Pike, University of Sussex
  Presenting Author