Visual Acuity Testing

1. Visual Acuity Testing • Paired Preference Procedure • Forced Choice Preference Procedure • Optokinetic Nystagmus • Visual Evoked Potential– a form of ERP

2. Sensory Development • Can be used to study visual acuity

3. Vision Testing

4. Infant Acuity Testing

5. Infant Acuity Testing Davida Teller’s simple test card

6. ERP: Event Related Potentials

7. Event Related Potentials

8. Event Related Potential

9. Visual Evoked Potential

10. Infant Vision Testing

11. Acuity Development

12. At 12 mo. At birth Development of Acuity At 3 mo.

13. Visual Acuity • At birth, acuity is approximately 20/400 to 20/800 • By 4 to 5 months infants are no longer “legally blind” (e.g., 20/200) • Reaches 20/20 between 8 to months • VEP suggests faster development– why?

14. What Infants See

15. Other Visual Limitations • Can only see high contrast stimuli

16. Contrast Sensitivity Functions

17. What infants see

18. Why is vision so poor? • Is it the eye? • Cornea • Astigmatism • Iris • Lens • Retina

19. Changes in Cones

20. Cone Development

21. Scanning • Research on externality effect

22. Scanning in Newborns

23. Why is vision so poor?

24. Color Vision • When can babies discriminate color? • Separating Hue, Brightness & Saturation • Categorical Perception of Color • R O Y G B I V

25. Can Infants discriminate color? • Problem in determining color discrimination • Color and Brightness are two independent aspects of any image • Confounding color differences with brightness differences – are infants (or adults) discriminating differences on brightness or color? • Brightness is a perceptual characteristic not simply a physical characteristic– must be determined by testing vision • Solution – in adults. • 1) Have adults match different colors for brightness • 2) Compare different colors previously matched for brightness

26. Matching Brightness – adjust the brightness (not hue) of the inner circle to match that of the outer one

27. Testing for Red/Green Color Blindness

28. Can Infants discriminate color? – cont. • Problems with adult solution to brightness/color confound for infant testing • Can’t ask infants to ignore color and compare only brightness • Can’t use adult matching data to apply to infants. Brightness likely differ considerably for babies – because of pigmentation in infants’ eyes. • Brightness matches even from one adult to another and likely same for babies – must test each individual separately • Solution – use a clever habituation task to get babies to IGNORE brightness

29. Infant Color Discrimination Task

30. Color Categories

31. Auditory Thresholds • Tested with High Amplitude Sucking Procedure • Newborns hear above 27 decibels • Can discriminate about 1 note on the musical scale

32. L R Sound Localization – cont. Sound louder and sooner to left ear

33. Newborn Speech Perception • H.A.S. procedure is also used to study speech perception • P. Eimas: Can newborn discriminate “B” from “P” sounds • Can infants discriminate “R from “L” • Or Pittsburgher’s Harry from Hairy

34. BP THAI

35. Dialect

36. PGH

37. Early Speech Perception • Is this a innate specialized ability? • Abstraction of ongoing speech • Invariance over individuals, gender, dialect • Dialect Study (At 11 mo but not 4) • Pittsburgh babies can’t discriminate Chinese from Taiwanese • Can discriminate Pgh from New York • Can discriminate 2 novel dialects (Southern from New York)

38. Newborn Taste Abilities • Can newborns discriminate the four basic flavors of : • Sweet, Sour, Bitter, Salty • Newborns prefer sweet and salty—why? • Sweet flavors can sooth the newborn

39. Newborn Smell • Newborns react positively and negatively to different smells • Can infants detect the smell of their mothers?

40. World of the Newborn • What is the world of a newborn like? • How does this effect opinion about imitation research?