week 5: visual perception and motor development in infancy

key theorists:

• piaget - child as an active learner discovering their world in pre programmed developmental stage

• vygotsky - social emphasis, tools/culture

• esther thelen - literally everything matters

dynamic systems theory:

• 1980s-1990s - moved towards how development happens rather than what changes across development

• spencer at al - “change occurs within complex systems w/ many components interacting over multiple timescales”

• a theory of development needs to account for:

  • complexity (soft assembly of skills)

  • continuity in time (compounding of skills)

  • stability (habitual states around which behaviour coheres)

  • non linear change (disappearing reflexes etc)

• the individual is a complex dynamic system (see slides for diagram)

• behaviour is emergent and multicausal

• self organisation generates novelty and creativity

• nested and interactive timescales

  • neural excitation: less than milliseconds

  • reaction times: roughly milliseconds

  • habituation: seconds/minutes

  • developmental growth: days-years

  • evolutionary change: centuries-millennia

• periods of stability vs transition

• variability = individual history

• attractors = period of stability towards which development tends to move

• soft assembly = bringing many things together to form a given behaviour

• complex system = identifying how components interact rather than focusing on what components are involved

• strengths:

  • revolutionary change - behaviour isn’t fixed

  • brain is not the controller - insight into embodied cognitive dynamics

  • interventions informed based on here-and-now activities impacting long term change

• challenges

  • defines all components as softly assembled into the system

  • focuses on identifying a cause

  • theories connect across multiple levels of analysis

  • integrates different timescales

dynamic systems theory and motor development:

• motor skills are interrelated

  • new ones are a product of prior ones

  • and will contribute to new ones in the future

• motor skills are individualised

• presence vs absence of skills

• 2 types of motor skills:

  • gross motor = control over actions that help infants get around in the environment

  • fine motor = refined gross motor skills

disappearing reflexes - stepping reflex

• stepping reflexes when babies are placed upright on a hard surface

• traditional linear development theories don’t account for this

  • babies with reflex lose it when leg weights are added

  • babies without reflex get it back in water

  • therefore likely to do with gravity/bodyweight/muscle strength

soft assembly of stepping reflex:

• physical = bodyweight, muscle strength to lift legs, later gain balance

• environmental = gravity (upright vs supine vs in water)

• cognitive = later gain motivation to lift legs

• social = later gain social encouragement

reaching

• 7 weeks: pre reaching

• 3-4 months: purposeful arm movements

  • improves with depth perception and greater control of arms

• 7 months: arms can move independently of each other

• fully developed by 8 months - motivational factors in the environment

soft assembly of reaching:

• physical = muscle tone to lift arms, motor control to direct reach, balance control

• environmental = stimuli to reach for

• cognitive = motivation to reach for something/depth perception

• social = encouragement/praise, competition

dynamic systems theory of visual perception:

• visual perception important for:

  • exploration of space

  • cognitive learning for motor development

  • most under developed sense at birth

• 4 ways of measuring visual perception

  • visual preference = two+ stimuli presented together, preference is indicated by gaze direction/looking time

  • habituation = stimulus repeatedly presented until infant no longer attends to it, responding to new stimulus when presented with old stimulus shows discrimination

  • physiological responses = ERP, heart rate etc

  • visual reinforcement = infant given control over stimulus

• aspects of visual perception

  • visual acuity - limited at birth

    • objects 25cm in front of infants can be seen clearly

    • infants younger than 7 weeks are likely unable to process full range of colour info

    • preference for high contrast

  • eye movements

    • smooth pursuit develops - gaze moves at the same speed as an object by 4-5 months

    • looking and focusing accurately by 3 months

  • colour perception

    • children can tell red and green apart by 8 weeks

    • full colour vision by 6 months old

    • younger than this tend to use shape rather than colour to differentiate objects

  • depth perception = ability to judge distance of objects from one another and from ourselves

    • 3-4 weeks = motion as a cue to depth

    • 2-3 months = binocular depth cues

    • 3-4 months = pictorial depth cues

  • pattern perception

    • face recognition - newborns prefer face like stimuli

    • demonstrate preference for mother’s face

    • prefer top heavy stimulus patterns

    • social information - sensitive to faces/voices/eye contact

    • by 2 months they focus on eyes and mouth

    • still face paradigm

  • object perception

    • size constancy = seeing an object as its real size, even when viewing distance varies

    • gets better over age

    • shape constancy = ability to perceive an object as being the same shape despite changes in its orientation