Perceptual Development in Infancy

n Our knowledge of the world revolves around the ways we interpret sensory information

n Much of what we perceive is processed implicitly without our awareness

n Yet, is has a major impact on how we process information and ultimately who we are as humans

n How do we know what is music or noise

n Why do we react to colors differently

n What do we find attractive

An infant’s world

How do you know what this is?

Theoretical Positions

n Empiricists/Constructivists: All of perception is learned through active interactions in the world and cultural transmission

n Gestalt Psychologist: Perception is learned except for figure/ground distinctions

n Nativists: Perceptual Abilities are all innate

n James & Elinore Gibson:

n Perception is innate, and infants naturally perceive “affordances” or important environmental information.

Theoretical Positions: What the data will show

n Many perceptual abilities are innate as argued by Gibson

n This is especially true with respect to abilities that apply to all member of the species and is probably related to both genetic canalization and brain growth

n Other abilities are learned, but through innate mechanisms (e.g., language, face perception)

n These are probably universal for the specie, yet have cultural influences

n Finally, other abilities are probably completely learned and culturally dependent

Depth Perception

n Consider the simple ability to perceive depth

History of Nativist-Empiricist Debate

n DeCartes (1638): Humans are born with “natural” laws that can measure the angle of the eyes, e.g., we are built with trigonometric tables in our heads

Nativist-Empiricist Debate

n Berkeley (1709):Argured for empiricism: Infants learn depth through feedback from their tactile and motor experiences. They associate eye movements with hand and arm movements.

n Touch Teaches Vision!

Nativist-Empiricist Debate

n Immanuel Kant (1881): Mind doesn’t rely on experience for meaning but innately organizes sensations into perception

n Depth perception emerges too early in life to have been learned

n Even adults with limited experience (e.g., handicapped) experience depth

How to empirically study this?

n In the 1960’s Gibson used the visual cliff “Common sense might suggest that the child learns to recognize falling-off places by experience—that is, by falling and hurting himself. But is experience really the teacher? Or is the ability to perceive and avoid a brink part of the child’s original endowment?”

The Visual Cliff

Visual Cliff Research

n Gibson concluded: So few infants crossed the “deep” side that it must be innate

n Bertenthal and Campos: 2 month olds show heart rate decrease when put on the “deep” side. This suggest they can perceive depth but are not afraid

n Fear develops late based on parents and “social referencing”

Looming

n When the size of an object increases explosively towards you, there’s a reflexive response to blink and make an avoidant movement.

n Gibson argued this response is innate and depends on peripheral information

n Despite early research suggesting that infants show avoidant head movements by 2 months, more recent work by A. Yonas showed this response is not present until about 8 months

Looming

n However, blinking responses to sudden magnification is present by 2 months of age (Yonas)

n Work with premature infants suggest this is an innate skill.

How do we perceive depth?

Oculomotor Cues

n Accomodation and Convergence both begin at approximately two months of age and provide infants with depth information

n Both only provide information about close-up distances

How do we perceive depth?

Binocular: Retinal Disparity

Binocular: Retinal Disparity

Binocular: Retinal Disparity

n Richard Aslin: Research showing infants 3-D movies while wearing glasses

n Infants by 4 to 6 months perceive and use retinal disparity

n Probably an innate skill that shows later maturation

How do we perceive depth?

How do you perceive depth

Texture Gradient

n Texture decreases with distance

Relative Size

n Size decreases with distance and can be compared with known objects

Interposition

n Contours of one object partially occlude another object

Shading

n Farther away objects appear darker

Pictorial or Monocular Cues

n Yonas & Granrud: Studies using infants reaching when objects appear at different distances because of pictorial cues

n Sensitivity to these cues emerge around 7 months of age

n Are they learned or innate?

n Gibson would argue they are affordances that don’t get “triggered” until this age

n Uniformity of development suggests this may be true

Perception of Pattern or Figures

n How do we perceive figure vs background?

What do you perceive?

How do you know what is figure or ground?

Gestalt School of Perception

n Must be innate rules to organize figure from background

Perception of Complete Figures

Subjective Contours Illusion: Infants perceive by 3 to 4 months

Goodness of Form

What about movement?

n Study by Kellman & Spelke