Single-case neuropsychological studies, such as those of H.M. and K.C., have been foundational in advancing our understanding of memory and cognition. However, the reliance on individual patients can introduce biases, as investigators may inadvertently emphasize findings that align with their hypotheses while neglecting alternative interpretations. For example, the focus on H.M.’s preserved remote memories led to decades of emphasis on consolidation models of memory, often at the expense of exploring alternative frameworks. This focus also delayed recognition of the hippocampus’s role in navigation and spatial cognition, which is now widely acknowledged.

Single-case studies are often fraught with challenges related to replicability and accessibility. By their nature, these studies cannot be replicated independently, making it difficult to confirm findings or test competing interpretations. Dominance by individual research groups, who may act as gatekeepers to a subject, can restrict access to data and hinder broader scientific collaboration. This approach runs counter to modern principles of open science, where data sharing and transparency are prioritized to foster collective scrutiny and progress. Without independent validation, conclusions drawn from single cases risk becoming entrenched, disproportionately shaping the direction of research.

While single-case studies provide invaluable insights, their findings should be interpreted with caution and situated within a broader context of evidence. Collaborative investigations, open data sharing, and attention to diverse hypotheses can reduce biases and enrich the interpretation of results. By complementing single-case findings with systematic approaches, such as group studies and meta-analyses, researchers can ensure a more comprehensive and balanced understanding of brain function, avoiding the pitfalls of overgeneralization and theoretical entrenchment.