title: Tipping points? Curvilinear associations between activity level and mental development in toddlers.
abstract: BACKGROUND
  The Theory of Optimal Stimulation (Zentall & Zentall, Psychological Bulletin, 94, 1983, 446) posits that the relation between activity level (AL) and cognitive performance follows an inverted U shape where midrange AL predicts better cognitive performance than AL at the extremes.
  
  
  METHODS
  We explored this by fitting linear and quadratic models predicting mental development from AL assessed via multiple methods (parent ratings, observations, and actigraphs) and across multiple situations (laboratory play, laboratory test, home) in over 600 twins (2- and 3-year olds).
  
  
  RESULTS
  Only observed AL in the laboratory was curvilinearly related to mental development scores. Results replicated across situations, age, and twin samples, providing strong support for the optimal stimulation model for this measure of AL in early childhood.
  
  
  CONCLUSIONS
  Different measures of AL provide different information. Observations of AL which include both qualitative and quantitative aspects of AL within structured situations are able to capture beneficial aspects of normative AL as well as detriments of both low and high AL.
authors.affiliation: Psychological and Brain Sciences, Boston University, Boston, MA, USA.
authors.forename: Megan
authors.initials: M
authors.lastname: Flom
authors.affiliation: Psychological and Brain Sciences, Boston University, Boston, MA, USA.
authors.forename: Madeleine
authors.initials: M
authors.lastname: Cohen
authors.affiliation: Psychological and Brain Sciences, Boston University, Boston, MA, USA.
authors.forename: Kimberly J
authors.initials: KJ
authors.lastname: Saudino
mesh_terms: D002657:Child Development / Q000502:physiology*; D002675:Child, Preschool; D003071:Cognition / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D015233:Models, Statistical; D009043:Motor Activity / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D012042:Registries
keywords: Activity level; curvilinear; early childhood; mental development; optimal stimulation model