''Small group PETting'': Sample sizes in brain mapping research

This comment originates from our concern about the extraordinarily small sample sizes in brain mapping research. To objectively investigate this topic, we analyzed sample sizes of the 410 studies in the official abstracts book of the First International Conference on Functional Mapping of the Human Brain. The percentage of investigations relying on very small samples is alarmingly high (median of sample sizes is 8.5). In 30.3% of the studies, the number of authors equals or exceeds the number of subjects. We discuss possible reasons for and dangers of this ''small sample practice'' and make a point for investing more time and effort in data acquisition. (C) 1997 Wiley-Liss, Inc.