3 - Brain and Senses Flashcards
Define Sensation and Perception
Sensation
- the biological mechanism of gathering information
Perception
- interpreting the sensory information
Vision Development (3 levels)
Low-level processing
- brightness (retina)
Mid-level processing
- colour (in midbrain structures)
High-level processing
- identifying faces (visual cortex)
Habituation and Dishabituation
Habituation
- tendency to repeatedly attend to a stimulus
> tendency decreases with exposure
Dishabituation
- heightened effect of a new stimulus compared to a habituated stimulus
Newborn Vision
- can detect brightness by day 2
- can detect movement and can track objects
- can detect patterns
> using scanning
> attracted to more complex patterns - visual acuity varies at 1m
> reaches adult level at 1y - limited colour vision until 3m
Visual Acuity
The sharpness of vision (ability to differentiate) - contrast - representing lines and shadows - picking out shapes
- visual acuity is adult-like at 1y
Testing babies’ visual acuity (4 methods)
Preferential Looking Method:
- babies prefer looking at some displays more than others
> tested by tracking vision between 2 stimuli
- if they have acuity, they will likely prefer the more complex patterns
Habituation Method:
- show the same image until the baby habituates (stops looking)
- show a new image to see if it dishabituates
- measure the looking time between stimuli
> if there is a difference in looking time, the baby must be able to differentiate between the stimuli
Optokinetic Nystagmus Method:
- measures the jumping of the eye when watching moving objects
- uses a panel of stripes
> when the stripes are too close, the eye stops jumping between stripes
+ this shows the level of differentiation (acuity) and tracking ability
Visually Evoked Potential Method:
- measures brain response to visual stimulus
- uses rapid alternation between grey background and stripes
- measures the level at which the baby can differentiate stripes from the background
Results:
- the different methods produce different results
> could be from measuring slightly different things
> could be that some tests are better
- Visually Evoked Potential Method (VEP) seems to show the highest level of visual development
Development of Visual Acuity
Infants have Astigmatism (a non-curved lens)
- so the light rays do not meet at a focus point on the retina
- the brain deduces that this blurry image is due to the eye being too small, thus causing the eyes to grow larger
> thus eye growth is determined by visual acuity (impact)
This can be shown in chicks, where showing them blurry images causes them to grow larger eyes
- thus environmental factors are crucial for normal visual development
> discrete development
Depth Perception (3 cues)
Dynamic Cues
- depth perception due to movement of the observer or observed object
> infants can determine looming (closer objects are bigger)
> at 3.5m they can discern motion parallax (when moving past objects, closer objects move faster than further ones)
Binocular Cues (binocular parallax)
- depth perception due to binocular disparity
> differences in visual input from left and right eyes
- and convergence
> more intense muscle contraction in the eye when focussing on closer objects indicates the object is closer - and stereopsis
> fusing of images from both eyes into one image (the further the object, the better the fusing)
Pictorial Cues (monocular) - interposition > ability to differentiate depth based on one object being in front of another
- linear perspective
> two parallel lines seem to get closer as they near the horizon (vanishing point) - size ratio
> ability to infer relatively how close similar objects are based on their size
Visual Cliff Experiment
goats can identify cliff edges from birth, can humans?
Experiment
crawl on
- top of the box has a check pattern on half and glass on half
- underneath the glass is a drop then an enlarged check pattern
> such that the squares will look the same size if you’re using Pictorial cues
> the drop will look large if your using motion parallax cues
Results:
- all babies made it to the half way
- most did not move over the visual cliff
> shows that the babies were using motion parallax cues through crawling
Order of Depth Cues development
- Dynamic Cues (looming + motion parallax)
- Binocular Cues (visual disparity + convergence + stereopsis)
- Pictorial Cues (interposition + linear perspective + size ratio)
Development of Face Recognition and preference
Both human and monkey babies
- prefer normal faces to scrambles
- prefer mother’s face
- prefer happy faces
At 3m, babies:
- prefer well proportioned faces to distorted
- prefer faces of their own race
- prefer female to male
Why do 3month old babies prefer female faces to male?
As infants get older, they focus on processing stimuli that are relevant and important to them
- in this case, sustenance
When does Perceptual Specialisation occur?
Within the 1st year
Babies’ hearing and preference
Infants focus on stimuli that are relevant to them
In this case auditory
Babies can hear in utero
At birth, they:
- prefer the mother’s voice
- prefer stories they heard in the womb
- can differentiate their own language from others, due to rhythmic differences
> they have difficulty differentiating languages with similar rhythmic patterns
- are less sensitive to low-pitched sounds
- prefer melodic music
> will vary sucking pattern to music - more sensitive to human voices and particular pitches
> due to motherese - prefer natural sounds to synthetic
Sound Localisation:
- from birth, infants are able to turn their heads towards a sound (a reflex)
- this sound localisation ability disappears at 2m, and returns at 4m more developed
Define Motherese
The particular way a mother interacts vocally with her baby
