Week 5

Question 1

Explain psychophysics

Answer 1

Psychophysics describes the relationship between the physical energy in the environment and the psychological experience of that energy.

Question 2

What is the absolute threshold

Answer 2

The absolute threshold is the smallest amount of physical energy a sensory system can detect.

Question 3

What is the difference threshold

Answer 3

The smallest difference between stimuli that we can detect is called the difference threshold, or the just-noticeable difference (JND).

Question 4

Describe Webers Law

Answer 4

the smallest detectable difference in stimulus energy is a constant fraction of the intensity of the stimulus. JND = KI, where K is the constant fraction and I is the intensity.

Question 5

Describe Magnitude estimation

Answer 5

Magnitude estimation is how our perception of stimulus intensity is related to the actual strength of the stimulus. The perception of magnitude is not absolute but relative. Our experience of one stimulus depends on its relationship to others.

Question 6

Describe Fechner’s Law

Answer 6

Fechner’s law says that constant increases in physical energy will produce smaller increases in perceived magnitude. For example, it only takes a small increase in volume to make a soft sound seem twice as loud, but it will take an incredible increase in volume to make a rock band seem twice as loud. This assumption applies to most, but not all stimuli.

Question 7

Describe Stevens’s power law

Answer 7

Stevens’s power law for magnitude estimation works for a wider array of stimuli. It includes a factor that takes into account the differential sensitivity of various sensory systems.

Question 8

Describe Signal detection theory

Answer 8

is a mathematical model of how a person’s sensitivity and response criterion combine to determine decisions about whether a near-threshold stimulus has occurred.

Question 9

Describe the computational model

Answer 9

tries to determine the computations that a computer would have to perform to solve perceptual problems to explain how complex computations of the nervous system turn raw sensory stimulation into a representation of the world. The computational approach focuses on the nervous system’s manipulations of incoming signals.

Question 10

Describe constructivist approach

Answer 10

argues that perceptual systems construct a representation of reality from fragments of sensory information. This representation is strongly influenced by learning, expectations, and inferences from past experiences, including culture.

Question 11

Describe ecological approach

Answer 11

most perceptual experience comes directly from the environment rather than from interpretations or expectations. Stimuli directly give most of the information needed to make sense of the world.

Question 12

Explain Perceptual organisation

Answer 12

is the task performed by the perceptual system to determine what stimuli go together to form an object. Your perceptual system can organise unconnected elements into objects by creating imaginary connecting lines called subjective contours.

Question 13

Explain figure-ground discrimination

Answer 13

When faced with complex stimuli, perceptual systems automatically pick out certain features, objects, or sounds to emphasise. This is called figure-ground discrimination. Figure is the emphasised features, and ground is the less meaningful background.

Question 14

Explain grouping

Answer 14

Perceptual systems group certain elements in the environment together, more or less automatically. Gestalt psychologists argue that people perceive sights and sounds as organised wholes. Gestalt principles that describe these grouping tendencies are:

Question 15

Proximity:

Answer 15

the closer the objects or events are to one another, the more likely they are to be perceived as belonging together

Question 16

Similarity:

Answer 16

similar elements are perceived to be part of a group.

Question 17

Continuity:

Answer 17

sensations that appear to create a continuous form are perceived as belonging together.

Question 18

Closure:

Answer 18

people tend to fill in missing contours to form a complete object.

Question 19

Texture:

Answer 19

stimuli that have the same texture (for example, oriented along the same directions) tend to be grouped together.

Question 20

Simplicity:

Answer 20

people group stimuli to provide the simplest interpretation of the world.

Question 21

Common fate:

Answer 21

objects that are moving in the same direction at the same speed are perceived as a group.

Question 22

Explain ocular accommodation

Answer 22

he muscles surrounding the lens either tighten (to make the lens more curved for focusing on close objects) or relax (to flatten the lens for focusing on more distant objects). Information from the muscles is relayed to the brain and helps create distance perception.

Question 23

Explain Eye convergence

Answer 23

involves each eye rotating inward to project the image of an object on each retina. Information about the rotation goes to the brain and the greater the rotation, the closer the object is perceived to be.

Question 24

Explain Retinal disparity

Answer 24

(binocular disparity), the difference between the two retinal images of an object (one from each eye), provides distance cues. This difference decreases with increasing distances. Depth can be created by showing each eye a separate photograph of a scene, each taken from a slightly different angle.

Question 25

Explain looming

Answer 25

a rapid expansion in the size of an image so that it fills the retina, is automatically perceived as an approaching stimulus and not an expanding object.

Question 26

Describe Hue

Answer 26

is the essential ‘colour’, determined by the dominant wavelength in the mixture of the light. Black, white, and grey are not considered hues because no wavelength predominates in them.

Question 27

Describe colour saturation

Answer 27

is related to the purity of a colour. A colour is more saturated and more pure if a single wavelength is more intense than other wavelengths. Pastels are colours that have been desaturated by the addition of whiteness.

Question 28

Describe brightness

Answer 28

refers to the overall intensity of all the wavelengths making up light.

Question 29

Explain Perceptual constancy

Answer 29

is the perception of objects as constant in size, shape, colour, and other properties despite changes in their retinal image.

Question 30

Explain size constancy

Answer 30

According to the computational view, size constancy occurs as objects move closer or farther away because the brain perceives the change in distance and automatically adjusts the perception. The perceived size of an object is equal to the size of the retinal image multiplied by the perceived distance.

Question 31

Explain Shape Constancy

Answer 31

Due to shape constancy an object appears the same even though the shape of its retinal image changes. The brain automatically integrates information about retinal images and distance as movement occurs. Expectations about the shape of objects also play a role in shape constancy. Shape constancy can also inhibit our ability to detect changes to objects

Question 32

Explain Brightness Constancy

Answer 32

Because of brightness constancy, no matter how the amount of light striking an object changes, its perceived brightness remains relatively constant. The brightness of an object is perceived in relation to its background.

Question 33

Explain top-down processing

Answer 33

Top-down processing is guided by knowledge, expectations, and other psychological factors.
People use their knowledge in making inferences or ‘educated guesses’ to recognise objects, words, or melodies, especially when sensory information is vague or ambiguous.

Question 34

Explain bottom-up processing

Answer 34

Bottom-up processing relies on specific, detailed information elements from the sensory receptors that are integrated and assembled into a whole.
Certain cells, feature detectors, respond to selected features of a stimulus. The stimulus is analysed into basic features before these features are recombined to create the perceptual experience. Features that are subject to separate analysis include orientation in space, colour, motion, and corners. In face recognition, not all features are equally weighted. We tend to rely on large-scale features, such as hair and head shape, to recognise people.

Question 35

Explain the key processes involved in attention

Answer 35

Attention is the process of directing and focusing certain psychological resources to enhance perception, performance, and mental experience. Attention directs our sensory and perceptual systems toward certain stimuli, selects specific information for further processing, ignores or screens out unwanted stimuli, allocates the mental energy to do the processing, and regulates the flow of resources necessary for performing a task or coordinating several tasks at once.