Perceptual Development

1
Perceptual Development

• Dr. Kline
• FSU-PC

2
(No Transcript)
3
Perceptual development is rapid!!!

• Perceptual abilities develop to adult-like or
  near-adult levels by the age of 6 months.
• In contrast, rarely do infants speak at 6 months,
  walk at 6 months, or can do fine-motor tasks at
  this time.
• Perceptual development may be launching pad for
  other aspects of development to occur (Sternberg).

4
Why is perception so important??

• Its the beginning of all behavior mental
  processing.
• You can produce movements, behaviors, or language
  if you dont have the physical apparatus to
  respond to objects events in your environment.
• We need to tie perceptions to actions
  (consequences of produced actions).

5
What is a sensation?

• Usually refers to the physical stimulus in the
  environment (light, sound waves).
• We convert physical energy from the world into
  neural energy our brains can process.

6
What is perception?

• Refers to how we interpret the stimulus
  information our nervous system takes in
  processes.

7
Does perception equal physical reality?

• What do you think???

8
(No Transcript)
9
(No Transcript)
10
(No Transcript)
11
(No Transcript)
12
(No Transcript)
13
Task of perception 3-Fold

• 1. Attending what in environment is
  interesting enough to examine in detail?
• 2. Identifying- can you determine what the
  stimulus is from past memory?
• 3. Locating how far away in what direction
  is the object or person from you?

14
Sternbergs example of the 3 tasks of perception.

• If you are in an Asian jungle and a tiger is
  charging, you need to orient your attention
  toward the tiger, to identify it as a tiger, and
  to locate how far away it is so that you can
  decide whether to climb a tree, shoot a gun, or
  pray. (p.93)

15
Visual perception-the basics

• Light- which can be thought of as discrete
  particles (photons) or traveling waves.

16
Human Visible Spectrum

• Humans can detect waves of energy traveling
  through space between 380 760 nanometers).
• Wavelengths outside this spectrum are
  undetectable to the human eye.
• Some organisms do detect wavelengths outside our
  visible spectrum.
• E.g., Rattlesnakes detect in infrared!
• bees detect ultraviolet light.

17
Electromagnetic Radiation
18
What are the 2 properties of light that influence
visual perception?

• 1. Wavelength is associated with our perception
  of color.
• 2. Intensity is associated with our perception of
  brightness.

19
Reflectance of light

• Light is reflected off of the surface of objects
  to the eye.
• Light energy is converted into neural energy
  then processed by the brain.

20
(No Transcript)
21
(No Transcript)
22
Visual Pathways

• 1. Geniculostriate pathway-
• optic chiasm----LGN---Primary Visual cortex
• involved in pattern perception, color
  vision
• 2. Tectopulvinar pathway-
• optic chiasm---superior colliculus---Lateral
• posterior pulvinar---PVC
• detection of light spatial orientation

23
Primary Visual Cortex
24
Common methods for examining infant perception
(visual, hearing, etc.)?

• 1. Preferential looking paradigm- infants will
  stare at objects or events they find interesting.
  
• E.g., an infant is presented with 2 faces Moms
  face a strangers face. The infants stare
  longer more intently at Mom.
• We can infer that the infant perceives the
  difference between his or her mothers face a
  strangers face as well as a clear preference for
  Mommy.

25
2. Habituation paradigm-

• Infants more likely to stare at a novel object
  than a familiar one.
• E.g., An infant is presented with 2 blue squares
  for 20 trials. On the 21st trial, a red square
  is presented in place of one of the blue squares.
  The infant spends significantly more time
  staring at the red square than the existing blue
  square.
• We can infer that the infant must be perceive the
  difference in the two colors (red blue) since
  the stimulus only differed on this one feature.

26
Attending to Visual patterns

• Infants may initially stare at a novel object
  (attention-drawing)
• But, will only continue to stare at it, if the
  object is meaningful (attention-holding).
• Cohen argues that while attention-drawing objects
  may be similar over the lifespan,
  attention-holding objects differ markedly with
  time.

27
What initially gets our attention?

• We attend to novel stimuli in the environment
  (bright lights, sounds, flashers).
• This orienting response called the orienting
  reflex, is present from birth.
• Why is this adaptive??

28
Do we need higher brain regions (cortex) to
orient?

• No!!! The presence of subcortical structures is
  enough to elicit orienting.
• Graham et al., used a habituation paradigm with
  speech sounds on an anencephalic infant (no
  cortex) found the infant showed orienting
  reflex.
• Anencephalic infants heart rate showed large
  decreases from baseline after a speech sound was
  presented. Response habituated after 6 stimulus
  presentations.

29
When scanning the environment, what do infants
look for?

• Very young infants (1 mos.) scan the edges of
  objects. They love contrasts ignore interiors.
  (e.g., outside views of face)
• Largely subcortical
• By 2 mos. Infants start focusing visual attention
  on the interior views of objects. (e.g., stare
  more at eyes mouth of a face, than on
  hairline).
• More cortical with time

30
What features of stimuli hold the infants
attention?

• Infants seek a moderate level of arousal in the
  environment (avoiding too much or too little
  stimulation).
• Evidence newborns given a choice among a dimly
  lit, moderately lit, or brightly lit object, tend
  to prefer the moderately lit object (Lewkowicz
  Turkewitz, 1981).

31
Visual acuity (fine-detailed vision)

• Newborns detect changes in brightness, movement
  in visual field, track moving objects.
• Visual acuity is assessed using a preference
  looking paradigm.
• If infants are presented with a uniform gray
  field black white stripes they prefer the
  stripes.
• By varying the distance between black white
  stripes having the infant compare this with the
  gray field you can assess the infants acuity.

32
(No Transcript)
33
Babies can discriminate the higher spatial
frequencies by 6 mos.

• Acuity is poor ( 20/200 to 20/800) in first
  couple of months of life. Images are blurry
  must be very close to babys eyes to be detected.
• By 6 mos. Acuity is near adult-levels.

34
Factors that increase acuity with age

• Pupil size increases
• Density of cones in fovea changes a birth these
  are spaced apart, but they migrate toward the
  fovea with time.

35
Do infants see colors?

• Yes!!!! 3-month-old infants can perceive
  most colors (reds, blues, greens).
• Evidence Bornstein repeatedly presented
  4-month-old infants with a specific wavelength
  until they habituated to it.
• He then presented one of 2 alternative
  wavelengths (A) one color which looked like a
  different shade of the same wavelength and (B)
  the other color which looked a different color
  than the original.
• Infants preferred looking B.

36
Do infants see in 3-D?

• Infant depth perception improves with experience,
  which is necessary for proper brain development.
• 3-5 mos.infants can coordinate their two eyes
  begin seeing depth as adults do using
  stereoscopic vision (Birch, 1993Mohn van
  Hof-van Duin, 1986).

37
Gibson Walk (1960) Visual Cliff Study

• Babies placed on elevated glass platform with a
  decorative pattern directly beneath the glass on
  one side (the shallow side) the same pattern
  several feet below the glass on the other side
  (the deep side).
• 6- 14 month-olds would not cross the deep side
  to get to their mothers even when encouraged to
  do so.

38
Infants viewing preferences

• 1. Human faces to other stimuli.
• 2. Mothers face to other faces.
• 3. Attractive faces to non-attractive faces.

39
Audition

• Infants well developed auditory systems, even
  before birth.
• Infants dont hear better than adults. Sounds
  need to be louder (10-17 dB) for infants to hear
  them.
• Infants hear high frequencies quite well (they
  are poor at detecting low frequencies) prefer
  to hear high-pitched voices.

40
What do infants prefer hearing?

• Musical sounds over non-musical sounds (infants
  alter sucking patterns to hear musical sounds
  over noise)
• High-pitched voices (Mother) vs. low-pitched
  voices.

41
Olfaction

• Newborns produced smiles to strawberry banana
  odors grimaces/ cries to rotten-egg fish
  odors (Steiner, 1979).
• Infants learn to prefer their mothers scent to
  other women.

42
Tactile

• Infants are very responsive to touch, like to be
  stroked and cuddled.
• Premature infants have better health outcomes
  (more likely to survive), if held stroked
  regularly.

43
Taste

• Newborns respond to all four taste sensations.
  
• Rosenstein Oster (1988) found that newborns
  produced distinct facial expressions in response
  to sweet, sour, bitter, salty substances.
• Infants prefer sweet tastes (milk).