An audio version of this article is available at NEJM.org A 13-year-old boy visits his pediatrician because his school football team requires medical clearance before the start of the season. On physical examination, his weight is 72 kg (above the 99th percentile for age and sex) and his height is 155 cm (the 50th percentile); his body-mass index (the weight in kilograms divided by the square o...

An echocardiographic evaluation of 77 members of a championship childhood swim team showed dimensional variations from normal in most athletes. Cardiac walls were thicker than the 95th percentile of normal: right ventricular anterior wall exceeded the 95th percentile in 100%, interventricular septum in 83% and left ventricular posterior wall in 91%. The left ventricular and left atrial cavities...

In simple, go/no-go, and choice reaction time (RT) tasks, responses are faster to two redundant targets than to a single target. This redundancy gain has been explained in terms of a race model assuming that whichever target is processed faster determines RT (Raab, 1962). Miller (1982) presented a race model inequality to test the race model by comparing the RT distributions of single and redun...