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
What were the results of earlier studies about motion perception 2 and what did it suggest 1?
- Infants preferred temporally modulated rather than stationary objects
- By 3 (behavioural results) to 6 (VEP results), infants have adult-like flicker sensitivity –> different visual functions develop at different rates
What did Mason 2003 found that also supported previous studies?
- Used coherent dot motion to look at motion perception using OKN (subconscious system) and FPL (conscious system)
- Result: OKN thresholds were consistently lower than FPL (better)
- -> supports that different visual functions develop at different rates
Why was the use of visual cliffs disapproved in binocular studies?
Used monocular cue illusion of size difference
When do infants have stereopsis?
Not at birth but present at 3 months (10-16wks)
What did Barbeito 1983 report about the sighting eye?
Infants tend to use the midpoint ie cyclops effect
- 30% in 3-4yo
- 10% in 4-5yo
- Perhaps due to laterality or preference
What are the 2 strongest evidence for poor vision in infancy and adulthood?
- Different visual systems develop at different rates
- Contour perception depends on signal to noise
Describe the dark glasses hypothesis and whether it is supported or flawed
- Newborn fovea absorbs 350x less light than adults thus, infants will have the same visual function as adults under a 350x brighter light
- F: infant VA does not increase with luminance greater than ambient illumination
Describe the visual efficiency hypothesis and whether it is supported or flawed
- States that visual function is dependent on foveal and post-receptoral immaturity thus all functions of vision will be affected equally (VA, CS, CV)
- F: partially accepted as some visual functions are also influenced by higher visual cortex
Describe the chromatic deficiency hypothesis and whether it is supported or flawed
- Magno (coarse detail and motion) systems develop before parvo (R/G and fine detail) systems
- If this was true, detection of colour difference should develop at a different rate to detection of brightness difference
- F: doesn’t explain anything else
Describe the subcortical function hypothesis and whether it is supported or flawed
- Vision is mediated by the sucortical (unconscious) system for the first few months and switches on at 2-3mths to see detail
- F: incorrect because cortical function has been demonstrated in young infants and premature babies
Describe the receptive field immaturity hypothesis and whether it is supported (6) or flawed
- LGN, SC and higher visual areas are immature from lack of learning (low sampling efficiency ie no pruning or lower neuron firing rate (from intrinsic noise reducing signal amplitudes)
- S:
- low acuity - lack of small, well organised rfs
- low CS - lack of spatial organisation
- low colour perception - lack of colour opponency
- low orientation and form perception - lack of simple and complex (requires overlapping rfs) cell arrangements
- low motion perception - lack of complex cell arrangements
- lack of stereopsis - inability to compare exact locations of right and left retinal images
How do infants use colour vision at 4 vs 6 months?
4mths: use colour for recognition of objects without preference for canonical colours until 6 mths
Identify the evidence for colour vision by 6 authors
- Williamson 2010: sort objects by colour at 3yo
- Johnson 1977: name colours prior to 3.5yo
- Ling and Dain 2008: 5yo can arrange and sort colours into series but with less precision than a 12yo
- Boon and Dain 2015: children prefer colour in books rather than other qualities. peak age 3.5-4yo
- Hayakawa 2011: Faster to detect snake in colour but accuracy is poorer with B/W –> 4.5-5.5yo prefer colours cognitively and may ignore other aspects
- Boon and Dain 2015: children of all ages like colour if it adds realism and aids in recognition
What is the conclusion about how babies and infants see the world?
Not only affected by maturity of ocular structures but also by maturity of connections between visual system and cognitive processes
