6: visual perceptual development Flashcards
how do we study visual perception
- preferential looking method
- habituation method
-both capitalize on the phenomenon that infants will look more at things they find interesting
what perceptual abilities develop
-visual acuity motion detection -scanning patterns -color perception -preferences for social stimuli
visual acuity
- how clearly infants can see (vision for fine detail)
- At birth, infants’ acuity is approximately 20/600 (Slater, 2001) – they see at 20 ft. what an adult with normal vision sees at 600 ft.
- the cutoff for legal blindness in adults is 20/200
visual acuity …methods and findings
- Measured with preferential looking: grey field vs. differently spaced black & white stripes
- Infants prefer stripes, but if acuity so poor that can’t see the stripes (blurs to grey), then will not prefer stripped field
-The distance between the stripes that is required to produce
a clear looking preference decreases (i.e., acuity increases), as infants age over birth-3yrs
motion detection
- infants can track faster moving objects soon after birth
- but infants have difficulty tracking slow-moving objects
motion detection…methods and findings
- Roessler & Dannemiller (1997)
- Preferential looking task with straight line and oscillating line
- Lines oscillated at slow (0.6 Hz) and fast (1.2 Hz) speeds of varying amplitudes (small to large)
- Measured preferences for moving lines in 6-, 12-, 18-, and 24-week olds
- Ability to perceive (i.e., show clear preference for) slow moving lines with smaller amplitudes increased as infants aged
scanning patterns
- babies younger than 2 months scan mostly around the external contours (that is, the outer edges) of objects
- 1-month-olds – look primarily at the outer edges of the face and head
- 2-month-olds – look at the internal features
color perception
- In adults, color perception is categorical.
- Wavelength (the physical stimulus) is continuous (400-700 nanometers).
- Color (the psychological dimension) is discrete (purple, blue, etc.).
color perception…methods and findings
- Infants who saw two wavelengths that cross a color boundary (e.g., blue to green) dishabituated and looked longer at the test stimulus.
- Infants who saw two wavelengths in the same color boundry (e.g., light blue to dark blue) did not dishabituate.
- Even newborns discriminate some color boundaries
- By 1 month, infants discriminate colors across the spectrum (e.g., blue, green, red, yellow) (just like adults)
- These color boundary discriminations occur even before infants have learned the names of the colors (with language).
- perceptual discriminations aree not dependent on linguistic organization
preferences for social stimuli
- newborns track a normal schematic face longer than a scrambled or a blank face
- preferences for faces is present event at birth
preferences for social stimuli….methods and findings
- Face preference becomes increasingly specific over 6-12 weeks
- ‘A’ is most face-like
- Infants’ preference for A over the less face-like ‘B’ increases from 6-12
role of experience in perceptual development
- experience expectant
- experience dependent
Rogers et al., 1981 research question..method
- does age of removal impact development of visual acuity?
- Tested infants’ visual acuity in typical infants and infants who had cataracts removed at different ages
- preferential looking task
Rogers results
-Infants with cataracts (IwC) who had surgery earlier than 8 weeks of age (and thus who started getting visual experience prior to age 8 weeks) developed acuity indistinguishable from infants without cataracts
IwCs who had surgery at 8 weeks or later had very poor acuity that did not improve with development
why is perception an important part of cognition?
- Perception is a basic cognition, fundamental to higher-level cognitions (you need to first perceive things to then remember them, reason about them, etc.)
- Perception is vital to gathering information and new understandings, which can lead to a cascade of development…
- perception + action = More complex understanding/expectations
