About this Research Topic
The history of Psychology is characterized by descriptions of individual cases. For instance, remarkable progress in cognitive neuropsychology has been possible through the study of patient Tan for language, patient P.G. for executive functions, patient H.M. for memory, and patient D.F. for vision. The detailed description of their profiles not only identified meaningful relations between brain dysfunctions and behaviors, but also allowed the formulation of models of normal functioning. Subsequent group studies confirmed and redefined these models, building up our present expertise.
Despite these important contributions from single case studies, this specific type of research is currently scarce. The number of articles describing single cases in psychology, neuropsychology, and cognitive neuropsychology has dramatically diminished over the last decade. Researchers themselves are well aware that publication of single-case studies is highly risky.
This could be the consequence of such factors as the increased use and popularity of neuroscientific methodologies requiring group studies. Indeed, neuroimaging studies successfully contribute to the understanding of the relationship between behaviors and brain activity. However, caution has been raised in that they fulfill this aim only when grounded on an explicit theoretical model. Another factor that might have discouraged the use of single cases is the limited awareness of the objective statistical measures that can be adopted in these cases. Common sense suggests that single cases are only a description. However, as suggested by McInthosh & Brooks (2011), statistical refinements provided by Crawford and colleagues beginning in 1988 allowed researchers to better solve this issue. For instance, a patient’s performance can be compared to a large sample of normative data or intra-individual comparisons can be performed. A similar statistical approach was recently suggested for the interpretation of fMRI data relative to individual subjects as compared to a normative sample.
Critically, history tells us that the unique contribution of single cases emerges in the early stage of experimental reasoning, during which observations towards hypothesis formulation are collected, rather than in the stage of collecting empirical evidence to support the same hypothesis. Moreover, single cases represent a detailed description of novel phenomena that should stimulate the theoretician to think about research areas that are not yet well-articulated. Single cases may also push upon the boundaries of different disciplines, with psychiatry and neurology being the most obvious examples.
This is clear in both clinical and research settings. In the former, clinicians are often faced with apparently puzzling phenomena such as individuals who should belong to a clear pathological category, but that instead challenge known theories and nosologies. In research settings, rare conditions still raise questions about the validity and completeness of our established models of functioning and treatment. In both settings, we argue that the intensive study of individual cases can lead not only to significant advances in basic knowledge of pathophysiological processes, but for clinical practice as well.
The human mind is still a mystery and researchers cannot accept that we have reached our maximum knowledge. As hypotheses and theories are the propeller of new knowledge, a culture promoting the sharing of ideas born through single case studies is not to be forgotten.
With this in mind, the aim of this Research Topic is to promote a renewed interest in the description of single cases (and multiple single-case studies) in psychology, neuropsychology, and cognitive neuropsychology that arise from both laboratory and clinical settings and which display strong methodologies and analyses.
Keywords: single-case design, neuropsychology, patients case studies, dissociation
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