• cognitive tests;
  • reliability;
  • sensitivity;
  • utility;
  • validity

This article considers the appropriate selection of cognitive tasks for research into the effects of nutrition and natural products on mental performance. It is recommended that tests appropriate to the domains of the cognitive function under investigation be used, and a set of criteria is provided to enable researchers to select appropriate tests and test systems for their research purposes. Research in this field is generally performed to establish whether products can produce beneficial effects on cognitive function, including optimizing development in pediatric populations, reversing existing cognitive deficits, preventing age-related declines, counteracting fatigue-based impairment, or simply improving performance above normal levels. The requirements of tests for these purposes are detailed, and evidence is presented that properly developed cognitive test procedures can be used in a range of normal and clinical populations, even in large, long-term studies and in a variety of cultures and languages.