Infancy_ Sensation _ Perception_ and Learning

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Infancy_ Sensation _ Perception_ and Learning Powered By Docstoc

 Dr. Kline
    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).
      Why is perception so important??

   It’s the beginning of all behavior & mental processing.

   You can produce movements, behaviors, or language if
    you don’t have the physical apparatus to respond to
    objects & events in your environment.

   We need to tie perceptions to actions (consequences of
    produced actions).
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.
What is perception?
   Refers to how we interpret the stimulus
    information our nervous system takes in &
Does perception equal physical
   What do you think???
    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?
Sternberg’s example of the 3 tasks of
   “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)
Visual perception-the basics
   Light- which can be thought of as discrete
    particles (photons) or traveling waves.
    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.
Electromagnetic Radiation
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.”
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.
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**
Primary Visual Cortex
       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: Mom’s face &
    a stranger’s face. The infants stare longer & more
    intently at Mom.

   We can infer that the infant perceives the difference
    between his or her mother’s face & a stranger’s face as
    well as a clear preference for Mommy.
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.
Attending to Visual patterns
   Infants may initially stare at a novel object

   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.
What initially gets our attention?

   We “attend” to novel stimuli in the
    environment (bright lights, sounds,

   This orienting response called the
    “orienting reflex,” is present from birth.

   Why is this adaptive??
     Do we need higher brain regions (cortex) to
   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 infant’s heart rate showed large
    decreases from baseline after a speech sound was
    presented. Response habituated after 6 stimulus
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
What features of stimuli hold the infants’
   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).
    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

   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.
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 baby’s eyes to be

   By 6 mos. Acuity is near adult-levels.
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.
      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.
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,
    1993;Mohn & van Hof-van Duin, 1986).
Gibson & Walk (1960): Visual Cliff
   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.
Infants viewing preferences:
   1. Human faces to other stimuli.

   2. Mother’s face to other faces.

   3. Attractive faces to non-attractive faces.
    Infants –well developed auditory systems,
     even before birth.

    Infants don’t 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.
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.

   Newborns produced “smiles” to strawberry
    & banana odors & grimaces/ cries to rotten-
    egg & fish odors (Steiner, 1979).

   Infants learn to prefer their mother’s scent
    to other women.

   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.
   Newborns respond to all four taste

   Rosenstein & Oster (1988) found that
    newborns produced distinct facial
    expressions in response to sweet, sour,
    bitter, & salty substances.

   Infants prefer sweet tastes (milk).