Examining Practice and Learning Effects With Serial Administration of the Clinical Reaction Time Test in Healthy Young Athletes.

Context: The clinical reaction time (RTclin) test has been recommended as a valid test for assessing concussion and determining recovery of reaction time function following concussion. However, it is unknown whether repeat assessment, as is used in postconcussion testing, is affected by learning or practice phenomena.

Objective: To determine if a practice or learning effect is present with serial administration of the RTclin test.

Further twists in gastropod shell evolution.

The manner in which a gastropod shell coils has long intrigued laypersons and scientists alike. In evolutionary biology, gastropod shells are among the best-studied palaeontological and neontological objects. A gastropod shell generally exhibits logarithmic spiral growth, right-handedness and coils tightly around a single axis.