title: The Enright phenomenon. Stereoscopic distortion of perceived driving speed induced by monocular pupil dilation.
abstract: OBJECTIVE
  The Enright phenomenon describes the distortion in speed perception experienced by an observer looking sideways from a moving vehicle when viewing with interocular differences in retinal image brightness, usually induced by neutral density filters. We investigated whether the Enright phenomenon could be induced with monocular pupil dilation using tropicamide.
  
  
  METHODS
  We tested 17 visually normal young adults on a closed road driving circuit. Participants were asked to travel at Goal Speeds of 40km/h and 60km/h while looking sideways from the vehicle with: (i) both eyes with undilated pupils; (ii) both eyes with dilated pupils; (iii) with the leading eye only dilated; and (iv) the trailing eye only dilated. For each condition we recorded actual driving speed.
  
  
  RESULTS
  With the pupil of the leading eye dilated participants drove significantly faster (by an average of 3.8km/h) than with both eyes dilated (p=0.02); with the trailing eye dilated participants drove significantly slower (by an average of 3.2km/h) than with both eyes dilated (p<0.001). The speed, with the leading eye dilated, was faster by an average of 7km/h than with the trailing eye dilated (p<0.001). There was no significant difference between driving speeds when viewing with both eyes either dilated or undilated (p=0.322).
  
  
  CONCLUSIONS
  Our results are the first to show a measurable change in driving behaviour following monocular pupil dilation and support predictions based on the Enright phenomenon.
authors.affiliation: School of Optometry and Vision Science, Queensland University of Technology, Victoria Park Rd, Kelvin Grove Q 4059, Australia; Institute of Health and Biomedical Innovation, Queensland University of Technology, 60 Musk Ave, Kelvin Grove Q 4059, Australia. Electronic address: a.carkeet@qut.edu.au.
authors.forename: Andrew
authors.initials: A
authors.lastname: Carkeet
authors.affiliation: School of Optometry and Vision Science, Queensland University of Technology, Victoria Park Rd, Kelvin Grove Q 4059, Australia; Institute of Health and Biomedical Innovation, Queensland University of Technology, 60 Musk Ave, Kelvin Grove Q 4059, Australia. Electronic address: j.wood@qut.edu.au.
authors.forename: Joanne M
authors.initials: JM
authors.lastname: Wood
authors.affiliation: School of Optometry and Vision Science, Queensland University of Technology, Victoria Park Rd, Kelvin Grove Q 4059, Australia. Electronic address: optom_kylie@hotmail.com.
authors.forename: Kylie M
authors.initials: KM
authors.lastname: McNeill
authors.affiliation: School of Optometry and Vision Science, Queensland University of Technology, Victoria Park Rd, Kelvin Grove Q 4059, Australia. Electronic address: hamish.mcneill@qut.edu.au.
authors.forename: Hamish J
authors.initials: HJ
authors.lastname: McNeill
authors.affiliation: School of Optometry and Vision Science, Queensland University of Technology, Victoria Park Rd, Kelvin Grove Q 4059, Australia. Electronic address: joanna.james@gmail.com.
authors.forename: Joanna A
authors.initials: JA
authors.lastname: James
authors.affiliation: School of Optometry and Vision Science, Queensland University of Technology, Victoria Park Rd, Kelvin Grove Q 4059, Australia. Electronic address: Leigh_vb@hotmail.com.
authors.forename: Leigh S
authors.initials: LS
authors.lastname: Holder
mesh_terms: D000328:Adult; D001334:Automobile Driving; D005260:Female; D006801:Humans; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D009184:Mydriatics / Q000494:pharmacology*; D009883:Ophthalmic Solutions; D010469:Perceptual Distortion / Q000502:physiology*; D011680:Pupil / Q000187:drug effects*; D014331:Tropicamide / Q000494:pharmacology*; D015348:Vision, Binocular / Q000502:physiology; D055815:Young Adult
chemical_list: D009184:Mydriatics; D009883:Ophthalmic Solutions; D014331:Tropicamide
keywords: Auto-movimiento; Conducción; Dilatación monocular; Distorsión de la velocidad; Driving; Enright; Monocular dilation; Pulfrich; Speed distortion