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Human development A. Normal perceptual development Earliest to mature (essentially “adult like” by 2 months) Temporal resolution (CFF) Light sensitivity Motion sensitivity Present by 4-6 months Color vision Stereopsis Maturing later (6+ months) Spatial vision (VA, contrast sensitivity, vernier acuity) Refractive error Accommodation and convergence Form perception B. Normal motor development Gross motor and language development General sequences in motor skills: Rolling over: 2-4 months of age Sitting without support: 5 to 7 months Standing while holding on to support: 5-10 months Pulling self to stand: 6-10 months Standing well without support: 10-14 months Walking well: 11-14 months General sequence in language Babbling Words Sentences Oculomotor Consistent eye turn: NEVER normal Large vergence and accommodative errors in younger infants Saccadic errors in younger infants Nasal bias in OKN and pursuit until about 6 months of age Vestibular function should be mature shortly after birth Visual perceptual-motor Piaget stages Sensorimotor (0-2 years): lack of fully developed object permanence (realization that objects continue to exist when not present Preoperational (2-7 years): beginning of internalized thought processes; logical thought not yet fully developed; beginning of sense of self C. Normal cognitive and social development Piaget’s stage of “concrete operations”: use of logical rules, begins fairly abruptly at about the time children start school Marked by ability to “conserve” or realize that the amount of a material does not change unless something is added or taken away even though its form may change Stage of “formal operations” begins around adolesence Ability to use abstract concepts, more flexible thought processes, deal with hypothetical situations Social Infants--temprament differences apparent early in life Facial muscles mature at birth; infants can smile, pout, etc. Attachment of infant and a consistent caretaker important “Terrible twos”: beginning of self awareness; become possessive of toys, etc., more complex social behavior School age: friendships become important, especially with peers of same sex and age D. Effects of early environmental restrictions Plasticity--not all functions begin to be plastic at the same time Not all cease to be plastic at 7 years Critical periods beginning at birth Absolute light threshold Temporal resolution (CFF) Peak contrast sensitivity Color vision Grating acuity Critical periods beginning between 3 and 4 months and continuing well into later childhood Directional discrimination (motion) Stereopsis Critical periods complete by 6 months Absolute light threshold Temporal resolution (CFF) Peak contrast sensitivity Animal models Only means to know effects on ocular dominance distribution and ocular dominance columns Both present at birth Deteriorate if normal binocular vision is impaired unilateral occlusion and strabismus have largest ffects Light and pattern deprivation Unilateral pattern deprivation alone can shift cortex to monocular state Monocular and binocular deprivation Monocular deprivation has more serious effects than binocular early in life Refractive error Uncorrected monocular AND binocular errors lead to amblyopia Hyperopic errors: more serious than myopic errors Smaller amounts need correction for normal development Strabismus Altenating: normal VA but reduced stereo Unilateral, constant: both VA and stereo reduced Cataract Unilateral even more serious than bilateral Unilateral ptosis is also serious