Sensory and Perceptual Abilities

1. Sensory and Perceptual Abilities

2. Sensory and perceptual abilities • In healthy, typically developing infants, the five senses are all functioning at birth • All are controlled by experience-expectant neurons • The quantity and quality of information newborns obtain through the senses and how it is organized and interpreted continue to be the subject of scientific debate and investigation

3. Why is this important to study? • Information is of practical use in medicine - To understand when development goes awry - A good measure of general level of maturation - To predict later cognitive development

4. Why is this important to study? • Relevant to traditional issues in psychology and philosophy concerning the basic nature of knowledge • To assess influences of environment on development • To understand other aspects of development, namely affective, linguistic, and cognitive

5. How are the sensory systems measured? • Preference technique • Habituation/ dishabituation • Discriminate learning (operant conditioning)

6. Visual perception • This is the least developed of all the senses at birth • The current cycle of interest in visual perception in infancy was stimulated by Fantz’s development of the visual preference technique. It is used to determine whether infants discriminate colors, brightness, patterns, depth, etc.

7. Visual exploration • Optokinetic Nystagmus (OKN): Occurs when a large target with a repetitive pattern on it moves past a stationary observer (vertical black and white stripes), or when an observer moves past a large pattern (a person moving in a car watching telephone poles).

8. What happens • The eyes fixate on some part of a pattern, follow that part with a smooth movement in the direction of the motion, then make a quick, jerky movement (saccade) back toward the center of the visual field in the direction opposite to that of the motion

9. OKN (cont). • OKN is involuntary, but can be voluntary • OKN is present in newborns, and its absence might be a sign of neurological damage

10. Saccades • Looking at a stimulus in the corner of the eye. A very rapid, usually accurate, movement that is ballistic (single motion from origin to predetermined endpoint) and brings peripheral stimuli into central focus (best vision) • Useful in detecting motion coming toward us, also useful in perusing. Basic physiological mechanisms for detecting and responding to stimuli in the periphery are present in newborns and develop rapidly in the early months of life.

11. Tracking and scanning • Infants are able to follow a moving object for about 90 degrees • Movement is slow and jerky • Improves to 180 degrees by 3 months • Infants scan the edges of objects and do not look at internal features • Infants prefer to look at angles over straight lines • Prefer vertical lines vs. horizontal lines • Prefer to look at a single feature of a complex figure • 1 month old babies scan contours and high contrasts • 2-3 month old babies scan interior of the face, especially the eyes and mouth—WHY?

12. Detecting visual information • -Brightness (almost as well as adults by 2 months) • -Color vision (not well until 3-4 months)

13. Pattern vision Acuity and accommodation: • The eyes of a newborn are shorter and flatter than those of adults • The cilliary muscles that control the lens do not function very well • These characteristics affect the infant’s ability to see clearly (acuity) and to bring objects into focus at various distances (accommodation) • Visual acuity at birth is 20/500

14. Pattern vision (cont). • By 12 months, acuity is 20/50 • Reaches 20/20 by 5 years of age • Development originally dependant on maturation, not experience • Visual accommodation is the adjustment of the shape of the lens of the eye to compensate for the distance of the object to focus from the retina • At birth, newborns see best, objects that are 7.5 inches away (mother’s face during feeding)

15. Development of face perception • Perception of schematic faces • Perception of real and photographic faces

16. Visual preferences • Prefer real faces over photographs • Prefer real faces over blank faces • Prefer real faces over scrambled faces • Prefer real faces over the face of a mannequin • Prefer medium lights over bright and dim lights prefer to look at horizontal lines vs. a bulls-eye target design • By two months of age, they prefer the bull’s eye-target

17. Objects in space • The role of movement in perception of objects • Visually guided reaching • Depth perception- starts to develop by 3-4 months

18. Depth perception • Involves seeing objects in 3-dimensions, judging size and distance, and perceiving heights (visual cliff) • Derives from each of our eyes seeing something different • Involves steropsis • Involves convergence-objects approach, eyes converge • Involves divergence- objects recede, eyes diverge • Both of the above (convergence & divergence) by 2 months

19. Studied by… • Observing response to “looming” and “zooming” objects • Visual cliff • By 6 months a baby won’t cross • A 2-3 month old shows an elevated heart rate when place on “cliff”

20. Auditory perception • Well developed before birth • For certain very low and very high frequencies, infants are more sensitive than adults • Less sensitive than adults to mid-range frequencies • Infants can hear high frequencies better than low frequencies until they are age 2 • Sound localization is worse due to head size • A 1 month old can discriminate similar sounds • Can recognize mother’s voice by the third day of life • Preference for mother’s voice over father’s voice

21. Tactile • By 32 weeks after conception, the entire body is sensitive to touch • Babies benefit from massage, especially preemies • Touch is very important in exploring- by six months babies are mouthing objects

22. Taste and Smell • Able to discriminate between sweet, salty, and bitter as early as 2 hours after delivery • Able to discriminate between breast pad used by mom and pad used by other woman by the 5th-6th day

23. Conclusion • Babies have amazing sensory abilities from the day that they are born. • Some are present before birth and others improve in the first few months of life.