Perceptual Development

1. Perceptual Development • Introduction • What is the infant’s phenomenological world like? • How can we answer this question? • Infant methodologies • Localization techniques • The orienting response • Visual localization • Auditory localization • Habituation/Dishabituation techniques • General habituation procedures • The fixed trials version • The infant-control procedure • Dependent measures of habituation • Cardiac deceleration • Visual fixation • Non-nutritive sucking • Operant condition procedures • Preference techniques • Research in perceptual development • Categories of infant capabilities • Sensory development • The perception of complex stimuli • Representational information • Depth perception – Albert Yonas • Kinetic information – complex • Binocular information – sensory • Pictorial cues – representational

2. Perceptual Development • Basic question: • What does the infant’s phenomenological consist of? • What does the infant perceive and how is it organized • Different types of question can be posed • Visual acuity • Color perception • Auditory localization • Perception of objects • Intermodal perception • Behaviors that allow for doing research with infants: • Engage in exploratory behavior • Preference for novel stimuli

3. Localization Techniques • The orienting response • Present infants with a stimulus • Measure their exploratory behavior towards the stimulus • Can include body turning, head turning, eye gaze • Visual localization • Present a visual target • Look to see if they try to fixate the target • Findings using localization technique • Auditory localization • Present an auditory target • Look to see if they try to fixate the target • Findings using localization technique

4. Habituation/Dishabitiuation Technique General Procedure Habituation Stimulus Dishabituation or Test Stimuli Test 1 Test 2

5. Habituation/Dishabituation Technique • Fixed-trials version: • Present infant with a preset number of exposures to the stimulus • Example: show stimulus 10 times, for 30 sec each • Then present test stimuli for set number of exposures • Problems with procedure • Infant control version: • Present stimulus and measure attention • When infant stops attending for set time, take stimulus away – 1 trial • Repeat procedure until attention drops below a preset criterion • Then present test stimuli for present number of exposures • Problems with procedure • Measures of infant attention • Cardiac deceleration • The mean number of heart beats per minute • Slowing down means increased attention • Visual fixation • The amount of time looking at a visual stimulus • Increased looking time means increased attention • Non-nutritive sucking • Sucking pressure on a stimulus • Changes in sucking pressure indicate changes in attention

6. Operant Conditioning Technique • Train infant to show a response to a stimulus: • Example: • Show stimulus A • Reinforce infants’ turning their head to look at a target • Test generalization of response by presenting a new stimulus • Show stimulus B • Look at whether infant makes trained response to new stimulus • The number of times infant makes a response to the new stimulus is a measure of the perceptual similarity between the two • If stimuli perceived as the same, response generalizes to new stimulus • If different, do not show trained response

7. Preferential Looking Technique • Present two stimuli: • Typically simultaneously, sometimes sequentially • Measure differences in attention to two different stimuli • Sometimes proceeded by a familiarization phase • Difference in attention between the two stimuli indicates perceived differences • Use in intermodal perception studies: • Present single stimulus in one modality (auditory or tactile) • Present two stimuli in second modality (visual) • Look to see if infants preferentially fixate as a function of the nature of the single stimulus • Preference for an intermodal match versus mismatch • Reinforce infants’ turning their head to look at a target • Violation of Expectation paradigm: • Present two visual stimuli • Expected (natural, familiar) • Unexpected (unnatural, novel) • See preferential fixation of unexpected stimulus • Indicates knowledge of basis by which unexpected stimulus is unusual or unexpected

8. Sensory Development Visual acuity Square Wave Grating Grey Field

9. Perception of Complex Stimuli Partly-occluded objects Kellman & Spelke (1983) Habituation Stimulus Test 2 Test 1

10. Depth Perception (Albert Yonas) • Kinetic information (Complex stimuli): • Looming • Accretion and deletion patterns • Perceived at birth (or shortly thereafter) • Binocular information (Sensory): • Binocular disparity • Convergence information • Perceived between 3 and 5 months • Pictorial Depth Cues (Representational information): • Cues used to represent depth in paintings • Familiar size, relative depth, linear perspective, interposition • Perceived by 7 months

11. Pictorial Depth Information Interposition Stimulus Control Stimulus