Infant perception

Question 1

What is a photoreceptor?

Answer 1

Specialized neurons found in the retina that convert light into electrical signals.

Question 2

Describe three features of rods.

Answer 2

1. Black and white luminance detectors.
2. Found across peripheral retina.
3. Work best in dim light conditions.

Question 3

Describe three features of cones.

Answer 3

1. Colour vision.
2. Concentrated in central retina.
3. Work best in bright light conditions.

Question 4

What is a limitation of the optic nerve myelination not being fully developed at birth?

Answer 4

As myelin provides a insulating layer around the nerve that allows the electrical impulse to travel quickly, when this layer is incomplete, the electrical impulse will not travel as efficiently along the nerve and this will have negative consequences for vision.

Question 5

Aside from the optic nerve myelination, what other part of the eye is poorly developed at birth?

Answer 5

The fovea.

Question 6

What is infants visual acuity at birth to 1 month, 6 months and 1 year?

Answer 6

Birth to 1 month old = 2/200.
6 months = 20/30.
1 year = 20/25.

Question 7

What is preferential reaching and how is it used?

Answer 7

Preferential reaching is using a baby’s reaching behaviour to measure their perceptual ability. It is used by placing different objects at different heights within reach of the baby, and observing and recording what the infant reaches for.

Question 8

How is an infants sucking behaviour used to measure visual perception?

Answer 8

Visual stimuli are presented to the infant and changes in sucking behaviour (occurrence, strength, rate) are monitored.

Question 9

What is an Electroencephalogram (EEG) used to measure and how does it do this?

Answer 9

EEGs are used to measure an infant’s brain activity.
EEG uses electrodes attached to the scalp to record the electrical activity in the brain when presented with visual stimuli.

Question 10

What is death perception?

Answer 10

Our ability to see things in 3D and to judge the distances of objects from our own bodies and from each other.

Question 11

What is optical looming and how is it used to test infant perception?

Answer 11

• Optical looming is a kinetic depth cue. When the retinal image cast by an object becomes larger over a short period of time, the object is perceived to be approaching the observer.
• If an infant blinks in response to a rapidly approaching object, we can assume that the infant has perceived the motion of the object.

Question 12

Describe Whites (1971) kinetic cues experiment.

Answer 12

White placed infants aged 1-5 months on their back in a crib and dropped a target towards the infant. Blink responses were recorded using electrodes placed around the eye. Only at 2-3 months of age did infants start to become more sensitive to depth from ocular looming.

Question 13

Describe Van der Weel and Van der Meer’s (2009) kinetic experiment.

Answer 13

They used EEG in an optical looming task. 5-7 month old infants did not have such well established responses to optical looming. 8-9 month old infants were at an in-between developmental stage. 10-11 month olds demonstrated well established responses to looming.

Question 14

What does Van der Weel and Van der Meer’s (2009) kinetic experiment suggest for development?

Answer 14

It suggests that from around eight months of age, the neural networks required for optical looming start to develop. This is important, because around eight months of age, infants typically start to crawl and it would therefore be important for them to have the ability to perceive impending collision.

Question 15

What did Granrud et al (1984) discover in his kinetic experiment?

Answer 15

That as surfaces move, the change in texture provides information about depth.

Question 16

Describe Granrud et al’s (1984) kinetic experiment.

Answer 16

He presented infants with computer-generated random dot displays. The only information about the contour of surfaces came from the movement of the textured displays. Infants aged 5 and 7 months reached for the apparently nearer surface.

Question 17

What is motion parallax?

Answer 17

Motion parallax is a depth cue that results from the motion of our own eyes or heads.

Question 18

What are the four depth perception cue areas?

Answer 18

1. Kinetic.
2. Binocular.
3. Oculomotor.
4. Monocular static.

Question 19

What is retinal disparity?

Answer 19

Two eyes displaced horizontally in the head. It is also a binocular depth cue.

Question 20

What is stereopsis and stereoacuity?

Answer 20

• Stereopsisis the combination of different retinal images.
• Stereoacuity is the measure of stereopsis.

Question 21

How do you measure stereopsis?

Answer 21

Two images are displaced horizontally and only one image is presented to each eye.
We can then measure stereopsis by determining how good a person is at fusing the different retinal images.

Question 22

Describe Held et al’s (1980) experiment of stereopsis.

Answer 22

Held measured infants’ sensitivity to binocular depth cues using virtual objects. Stereopsis was first demonstrable at 4 month old. By 5 months old, stereoacuity had improved to 1 minute of arc or better. Time course for the development of stereopsis is extremely rapid.

Question 23

List three monocular depth cues.

Answer 23

1. Relative height.
2. Relative size.
3. Interposition.

Question 24

Describe the relative height monocular depth cue.

Answer 24

Objects that are farther away appear to be nearer to the horizon than closer objects.

Question 25

Describe Arterberry’s (2008) relative height experiment.

Answer 25

Pairs of 3D plastic toys were hung at different heights on a board.
When viewed with one eye, if infants are able to use the relative height cue, they would perceive the toy placed at the bottom as closer than the toy at the top.
Under binocular conditions, as expected, infants reached equally for the two objects.
Under monocular conditions, infants aged 5 months and 7 months reached for the lower, apparently closer toy.

Question 26

Describe the monocular cue of relative size.

Answer 26

If we assume that two objects are the same size, we perceive the object that casts a smaller retinal image as farther away than the object that casts a larger retinal image.

Question 27

What age does the monocular death cue of relative height start to emerge?

Answer 27

5.5 months of age.

Question 28

Describe the monocular depth cue of interposition.

Answer 28

When one object overlaps or partly blocks our view of another object, we judge the covered object as being farther away from us and the covering object as being closer to us.

Question 29

Describe Granrud and Yonas (1984) interposition experiment.

Answer 29

‘Using preferential reaching, Granrud and Yonas (1984) tested infants’ sensitivity to interposition. If infants are sensitive to interposition, we would expect that they would reach for the side of the test display that is perceived as closer.
7 month old infants reached preferentially for the ‘closer’ object.
5 month old infants did not show significant differences in reaching preferences between the test and control displays.

Question 30

What did Adams, Courage and Mercer (1991) find when investigating infants colour perception?

Answer 30

A 3 month old infants could discriminate green and red but not 2 month old.

Question 31

Why can’t infants perceive colour from birth?

Answer 31

Infants possess all of the ‘machinery’ required for colour perception and they are instead limited by their reduced visual sensitivity.