Challenges to mean-based analysis in Psychology: The contrast between individual people and general science.

In a recent paper Speelman and McGann (2013) argued that psychology’s reliance on data analysis methods that are based on group averages has resulted in a science of group phenomena that may be misleading about the nature of and reasons for individual behaviour. The paper highlighted a tension between a science in search of general laws and the individual, variable and diverse nature of human behaviour and character. Two central traditions in psychology are challenged by this tension: (1) data is collected from a large number of people and distilled into a handful of parameters that reflect the middle of a distribution of scores and the average variation around that mid-point, and (2) theories are developed to explain the average performance of the group. The disjunction between group-based measurements and the actual psychology of individual people raises specific concerns in both research and applied professional domains of psychology. For instance, a clinician who reads in a report that Therapy A leads to a significantly greater improvement in depression than Therapy B might be tempted to adopt Therapy A in her practice. But what are the odds that Therapy A will be the best option for the next depressed client to walk in her door? What does an observation that, on average, people find it easier to identify letters presented on a screen when they are presented at the end of a word than when presented in isolation actually tell us about the specific cognitive processes occurring in specific people’s activities? Are we justified in interpreting this result as reflecting something about the way every person’s mind processes letters and words? To what extent should we explore the prevalence of this pattern of responding before we start making claims about cognitive mechanisms that are general to all humans? Speelman and McGann argued that more explicit and careful justifications are required for the common practice in psychology of extrapolating from average data to general laws, but also from general laws to explanations of individual behaviour. Given the ability of humans to adapt to their environments, it would seem unlikely that everyone would develop identical cognitive processes for any given task. As a result, developing general theories about any given task, and using those theories to develop methods for clinical interventions or educational purposes would seem a risky endeavour.


This Research Topic will explore this argument about the pitfalls of using the mean for the basis of psychological science. The problem is universal in its applicability to psychology and opinion papers, reviews and original empirical research from all areas of the discipline are welcome. Papers critical of Speelman and McGann’s argument as well as those with a focus on the various ways in which the tension between group-based and individually focused aspects of psychology might be overcome are particularly welcome.


Topics of interest including but are not limited to:
• The challenges that arise for applied and professional psychologists in bringing group-based research to bear in individual cases.
• The most valid and effective methods for applying the findings of group-based research to individual cases in different areas of psychology. (Do these vary between different sub-disciplines?)
• How the logics of group-based and individually focused research might be reconciled in the development of psychological theory.
• The kinds of research methods and logic we might adopt to optimize both scientific rigor and sensitivity to individual variability.
• How the tension between individual and group-based descriptions of psychology has affected the historical development of the science.
• Challenges for research design and statistical methods that arise from applying different levels of analysis.