Developmental Psychology - Perceptual Development

Developmental Psychology, Social & Developmental Psychology

Intro to perception (5 points)

• Perception is fundamental - knock-on effect to all other domains.

• Perception tells us what is out there - children to explore the world, decision-making, etc.

• Perception based on expectations as well as current input to retina.

• Allows for adaptive decisions, actions, social interactions.

• There is a continuum between perception, cognition and decision-making.

i-Cub in perception (3 points)

• Motors to interact with world, cameras to act as visual system, sensors on its hands.

• Performance is nowhere near typical human performance - difficult to build robots that function as efficiently as humans, that tell you something about how to build a perceptual system.

• However, the human brain is solving perceptual problems much faster and much more reliably than the best robotic systems.

Post-natal development of perception (5 points)

• Some sensation in the womb, but vast majority of input after birth.

• Development in terms of neural processing of signals coming in, not just eyes and ears.

• Structure and function of sensory organs, e.g. eyes, ears: minor changes.

• Structure and function of sensory brain areas: major changes.

• These changes depend on sensory experience.

Early visual abilities: at birth (2 points)

• Eye control: poor accommodation (focus), poor vergence (both eyes converging on same target), ‘jerky’ eye movements.

• Orients to patterns and faces, but limited visual acuity (ability to see detail) and contrast sensitivity.

Early visual abilities: 1-3 months (2 points)

• Development of better accommodation, vergence, and smooth eye movements for tracking moving targets.

• Better acuity and contrast sensitivity, emerging abilities to distinguish motion, orientations, patterns, and stereo (binocular) depth.

Early visual abilities: 4-8 months (2 points)

• Acuity and contrast sensitivity getting closer to adult levels.

• Global organisation of stimuli, e.g. coherent form and motion, biological motion, depth from pictorial cues.

Early auditory abilities: at birth (3 points)

• Recognise sounds and voices heard in utero.

• Prefers mother’s voice to stranger’s.

• Localise sounds in space.

Early auditory abilities: 1-3 months

Distinguish different speech sounds.

Early auditory abilities: 4-8 months (2 points)

• Increasing range of sensitivity to pitch (high and low).

• Distinguish auditory patterns, e.g. different pitches, rhythms, melodies.

Early auditory abilities: 9-12 months

Beginning to lose the ability to discriminate speech sounds not used in the language (→ perceptual narrowing).

Perceptual narrowing

The loss of the ability to discriminate speech sounds not used in a language - happens between 9-12 months after birth.

Smooth pursuit system - eye movements

Saccadic system - eye movements

Eye movements are controlled by…

Multiple cortical and subcortical networks.

Visual acuity

The range of patterns a person can see (the narrowing of the lines).

Contrast sensitivity

The range of contrasts a person can see. (making the black-white greyer).

An infant’s perception is relatively adult-like by…

6 months

The ability to detect contrast between light and dark improves with…

Age

True or false: Contrast sensitivity improves in a linear way

False: Contrast sensitivity improves in a non-linear way - huge improvement in first 10 weeks, levels off after this.

Atkinson & Braddick (2011) - visual acuity

Visual acuity development is not well explained by changes in the eye: “if the improvement of acuity from 1-month to adult is taken as 12-fold, only about 25% of this change can be attributed to the photoreceptors and to increasing eye size”

Visual deprivation in infancy

Permanent loss of acuity and contrast sensitivity because neurons in V1 do not acquire connections to inputs from the affected eye.

Visual evoked potential (VEP) (2 points)

• An EEG method to assess whether neurons are firing in response to a specific visual change, e.g. a change of orientation.

• The VEP responses are specific to the reversal frequency of stimuli presented.

Orientation VEP (2 points)

• Making some kind of change on every frame - less frequently making major change (orientation).

• Cortical activity is produced specifically by the orientation change (not random change) at ~3 weeks (Braddick, 1993).

Braddick (1993) - orientation VEP

Cortical activity is produced specifically by the orientation change (not random change) at ~3 weeks.

Motion VEP (2 points)

• Cortical activity is produced in response to directional motion emerge at ~10 weeks for low speeds and ~13 weeks for high speeds (Wattam-Bell, 1991) - suggests different aspects of visual processing develops at different rates.

• Experience is important: Kittens reared in stroboscopic illumination (no continuous motion) have no directional cells in visual cortex (Cynader, Berman & Hein, 1973; Pasternak et al, 1981) - need visual experience of continual motion to fine-tune cortical responses.

Wattam-Bell (1991) - motion VEP (2 points)

• Cortical activity is produced in response to directional motion emerge at ~10 weeks for low speeds and ~13 weeks for high speeds.

• Suggests different aspects of visual processing develops at different rates.

Cynader, Berman & Hein (1973); Pasternak et al. (1981) - motion VEP

Experience is important: Kittens reared in stroboscopic illumination (no continuous motion) have no directional cells in visual cortex - need visual experience of continual motion to fine-tune cortical responses.

Depth VEP

• Depth processing - stereoscopic - comparing tiny discrepancies between image on left and right eye to judge how in depth an object is.

• Often tested using red-green goggles (different images to the two eyes) vs. red-red goggles.

• Cortical responses emerge at ~11-13 weeks (Braddick & Atkinson 1983) - slightly later than motion processing.

• Depth detail - stereoacuity - improves greatly within 4-5 weeks of onset (Birch, Gwiazda & Held, 1982).

Braddick & Atkinson (1983) - depth VEP

Cortical responses emerge at ~11-13 weeks.

Birch, Gwiazda & Held (1982)

Depth detail - stereoacuity - improves greatly within 4-5 weeks of onset.

Johnson et al. (1991) - newborn face perception (2 points)

• Waved paddle over visual field of baby - looked at whether baby moved head/eyes to look at it.

• Newborn infants prefer standard faces over scrambled.

Johnson et al. (2005) - newborn face perception (4 points)

• Because newborn visual cortex is so immature, newborn face perception is likely to be driven by more basic and early developing sub-cortical mechanisms.

• By 2 months, face processing includes sub-cortical (‘conspec’) and cortical (‘conlern’) mechanisms working in parallel.

• Babies have good face detecting system in order to survive.

• Three squares - often used as controls, infants respond to it.

Reid et al. (2017) - newborn face perception (3 points)

• Preferences may emerge in the womb.

• Shine a light through mother's stomach - either has face-like configuration or bottom-heavy configuration.

• Infants turn their head towards face-like stimuli.

De Haan et al. (2002, 2003) - face perception (4 points)

• Adults: Inverted faces classed as objects by brain - bigger peak as they are processed as objects instead of faces.

• 6 months: No specialised response - human upright and inverted faces treated relatively similarly.

• Suggests that cortical system takes a long time to build up.

• Classic comparison is upright vs inverted faces. All the visual information is the same, so a differential response indicates activity specific to face processing. Contrast with another upright vs inverted object for further evidence that the activity is specific to face processing.

Ventral stream

Extracting visual detail, identifying objects - “what”

Dorsal stream

Dictates motion, spatial awareness, action - “where/how”

Braddick, Atkinson & Wattam-Bell (2003) - pattern perception

Patterns are processed in two parallel streams: dorsal stream (motion/space/action: “where/how”) & ventral stream (objects: “what”).

Braddick, Atkinson & Wattam-Bell (2003) - coherence (5 points)

• Form coherence - need fewer patterns to be lined up as age increases.

• Motion coherence - need around 40% coherence to see movement.

• Motion responses are poorer/ later than form in typical development.

• The dorsal stream (motion/space/action processing: “where/how”) has a longer, and more vulnerable development than the ventral (objects: “what”).

• Form and motion systems can intersect, so must be separated in testing.

Form coherence

Motion coherence

Perceptual narrowing - 6-8-month-old study

English 6- to 8-month-olds discriminate two Hindi sounds that adult English speakers cannot.

Werker & Tees (1984) - perceptual narrowing

English 10- to 12-month-olds no longer make the distinction between Hindi sounds, but Hindi infants do.

Gervain & Werker (2008) - perceptual narrowing

Studies on perceptual narrowing in infancy have been replicated many times with other languages and phoneme discriminations, both behavioural and ERP measures.

Pascalis et al. (2002) - perceptual narrowing

Young infants discriminate both human faces and monkey faces equally, but by 9 months respond more to a novel human face than a novel monkey face.

Perceptual narrowing

Infants lose their ability to make distinctions between unfamiliar sounds.

Statistical learning

The ability to rapidly learn the co-occurrence statistics (which items tend to go together) even in completely artificial stimuli.

Saffran et al. (1996) - statistical learning

8-month-olds were presented with auditory syllables for 2 minutes. Syllables were made to follow each other more often - they learned how to pick out regularities after 2 minutes of exposure.

Fiser & Aslin (2002) - statistical learning (4 points)

• Showed infants elements of objects, tended to put different shapes together.

• Always happened that same ones would be together.

• Later scenes - looking patterns indicated they expected them to be together again.

• Familiarity preference - looked more at patterns they'd seen before.

Redundant information (the same information across more than one sense) leads to faster/more accurate decisions through: (2 points)

• Flexibility - use one cue when other not available.

• Correlations between cues allow us to separate and attend to important objects.

Bahrick & Lickliter (2012) - multisensory development (2 points)

• Events that go together have “amodal” features in common such as temporal synchrony, rhythm, tempo.

• Young infants tune in to these redundantly specified, amodal properties of stimuli.

Bahrick & Lickliter (2009) - intersensory redundancy hypothesis (IRH) (2 points)

• The intersensory redundancy hypothesis (IRH) suggests that information presented in multiple sensory modalities at once (multimodal) is more easily attended to, learned, and remembered than information presented in a single modality (unimodal).

• “Young infants, with no prior knowledge of the world, rapidly come to perceive unitary events and attend to stimulation that is relevant to their needs and actions”.

Bahrick & Lickliter (2000) - multisensory development (2 points)

• 5-month-olds (n=8/gp) see and/or hear a hammer tapping a surface to a rhythm.

• After habituation looking time goes down, the rhythm changes. They noticed/learnt the rhythm better in the two-cue (audiovisual) condition than given single cues. Multisensory information guides attention and learning.

Bahrick & Watson (1985) - multisensory development

5-month-olds look longer at a live feed of their own legs than a prerecording of their own, or someone else’s, legs.

Rochat & Morgan (1995) - multisensory development

3-5-month-olds look longer when legs move in the opposite direction to their own.

Bahrick (2013) - multisensory development

While infants notice the visuomotor correlation, they may not relate it to their own body.

Zmyj et al. (2011) - multisensory development (3 points)

• Are infants able to detect the correspondence between tactile (felt) stroking on their own legs and viewed stroking on viewed legs?

• 10-month-olds, but not 7-month-olds, looked longer at the synchronous display.

• This suggests visual-tactile correspondence is used to perceive (identify) the body at 10 months.

Filippetti et al. (2013) - multisensory development (2 points)

• Used looking time to show that newborns detected visuotactile synchrony of stroking on their face and viewed strokes on another infant face.

• This is in line with adult work which shows that synchronous stroking on a viewed face and one’s own face can due adults can experience an ‘enfacement illusion’ (Tajadura-Jimenez, Longo, Coleman & Tsakiris (2012)).

Tajadura-Jimenez, Longo, Coleman & Tsakiris (2012) - multisensory development

Showed that synchronous stroking on a viewed face and one’s own face can due adults can experience an ‘enfacement illusion’.

Lewis (1999) - multisensory development

Children engage in mirror self-recognition only in the second year of life.

Perceptual discrimination isn’t the same as…

Subjective experience