How do babies see the world? Flashcards
What was Allen 1996 central and peripheral acuity experiment and what was their result 2?
n= 39 infants, 8 adults
Sweep VEP to measure their acuity and contrast sensitivity by changing the stimulus. 2 parts of the visual field was measured at the same time by conducting a reversal at 8 times/sec.
Result: cs and acuity develops similarly centrally and peripherally
Adams and courage 2002 experiment about CSF: 2 methods
2 alternative forced choice method.
Exp 1 = look at blank or target.
Result:
- Early infancy: CSF is low and shifted to the left (–> infants see objects that are 4-6x larger than adults)
- Infants see larger objects better than finer details
Exp 2 = left or right.
Result:
- Peak adult CSF =4.8cpd
- Infant CSF = 0.5-1cpd
- at high freq such as 30cpd, CS=0 –> more dramatic drop off than infants
What did Skoczenski and Norcia 2002 do and found out about vernier acuity? 3
- Sweep VEP
- Measured at V1
- Vernier and VA matured over the first 6 years but vernier matured by 14 years
What did Kovacs 1999 4 and Barker 2008 1 find out about contour integration?
Gabor patch stimulus
Barker: contours can be detached and meaning ascribed to the forms by 6 months but not at high levels of noise
Development of colour vision 2. What is the chromatic deficiency hypothesis?
- All 3 cones are functional at birth
- Newborns cannot discriminate unless there is a difference in brightness
- Stimuli must be isoluminant to test colour perception only
- Chromatic deficiency hypothesis: magno develops before parvo
Relationship between Kay pictures and Landolt C
At least twice the size
- Kay pictures are the more detailed one
Describe findings of Suttle 2002 about colour vision 3
- 2mth: needed brightness to see colour
- 3mth: starting to increase
- 4mth: 5 are above chance, 1 below chance = CVD, is still developing
Method and result 3 of boon about colour vision 2007
- Transient VEP in response to R/G patterns
- CS is higher when measured psychophysically than with transient VEP –> VEP (from retina to VC) morphology is immature and
- Sensitivity is lower in infants –> suggests that colour is processed at higher levels eg V4
- VEP patterns show positive and negative amp in adult m–> adults can elicit more complicated responses
Stimulus 1, result 2 from Knoblauch 2000’s experiment about CS and CV
Stimuli: chromaticity differences that falls along a deutan axis
Result:
- Chromatic CS improves during childhood
- Begins to decline from early adulthood 16-32 for deutan and tritan due to yellowing of lens
What was the stimulus used by Banton 2001 to assess direction perception 2
Direction VEP stimulus:
- Random dots, some moving in coherence with a patch moving in a different coherent direction
- Allows methods such as VEP to investigate motion discrimination
What did Braddick 2005 compare to orientation and direction VEP and what was their result 2?
- Compared orientation and direction VEP compared to noise amplitudes across a range of ages
Result: - Orientation: responses apparent after 6wks (SNR 2.7:1)
- Direction and motion: responses after 11-13wks (SNR 2.7:1)
4 reasons for immaturity of orientation and direction sensitivity
- Dots were difficult to see from VA
- Incomplete myelination in immature long-range horizontal connections in early infancy –> prevents precise timing needed for direction discrimination
- Immaturity of higher cortical areas for direction sensitivity
- Orientation sensitivity refined first because it may be more reliant on striate cortex
Development of orientation sensitivity 3 and who’s experiment proved that this characteristic is innate and not reflected by neural plasticity
- Later research using habituation showed that newborns can discriminate between horizontal and vertical and ability depends on spatial and temporal freq and contrast
- By 3 months, can differentiate orientations that differ by 5 degrees
- Leehey 1975: V and H differentiation is an innate characteristic
What were 2 variables that may have biased the outcome of these orientation sensitivity studies?
- Cells were not sampled in a range of locations
- Orientation sensitive cells are clustered so that sensitivity to a particular orientation are found close to one another
Describe Stryker and Shrek 1975 2, and Singer 1981 2 studies about orientation preference
- Exposed cats to V or H stripes
- Some cells preferred trained stimulus and some cells preferred untrained stimulus
- Exposed animals to restricted orientations
- More cells prefer the trained stimulus –> supports Hebb’s rule
