title: Salivary alpha-amylase levels and hyperbolic discounting in male humans.
abstract: OBJECTIVE
  Little is known regarding the role of the sympathetic-adrenal-medullary (SAM) system in self-control and impulsivity in intertemporal choice (delay discounting), although the roles of dopaminergic and serotonergic systems have been extensively examined. This study was aimed to examine the relationships between salivary alpha-amylase (sAA, a non-invasive biological marker of adrenergic/SAM activities) levels and hyperbolic discounting, which is of interest in psychoneuroendocrinology and neuroeconomics.
  
  
  METHODS
  We assessed degrees to which delayed monetary gains were discounted (hyperbolic discount rates) in healthy male students. Participants' sAA were also assessed.
  
  
  RESULTS
  We observed negative relationships between sAA and hyperbolic discounting of small, medium, and large monetary gains.
  
  
  CONCLUSIONS
  The results indicate that subjects with low sAA are impulsive in intertemporal choice. Implications for the roles of adrenergic and SAM systems in self-control in intertemporal choice are discussed.
authors.affiliation: Department of Cognitive and Behavioral Science, Graduate School of Arts and Sciences, University of Tokyo, Tokyo, Japan. taiki@ecs.c.u-tokyo.ac.jp
authors.forename: Taiki
authors.initials: T
authors.lastname: Takahashi
authors.forename: Koki
authors.initials: K
authors.lastname: Ikeda
authors.forename: Hirokata
authors.initials: H
authors.lastname: Fukushima
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Hasegawa
mesh_terms: D000293:Adolescent; D000313:Adrenal Medulla / Q000502:physiology*; D000328:Adult; D002755:Choice Behavior / Q000502:physiology; D006801:Humans; D007175:Impulsive Behavior / Q000378:metabolism* / Q000503:physiopathology / Q000523:psychology*; D008297:Male; D012463:Saliva / Q000737:chemistry; D013564:Sympathetic Nervous System / Q000502:physiology; D013739:Testosterone / Q000378:metabolism; D000516:alpha-Amylases / Q000032:analysis / Q000378:metabolism*
chemical_list: D013739:Testosterone; D000516:alpha-Amylases