Chapter 1: Introduction to Perception

Question 1

Define the term perception.

Answer 1

Perception: the experiences that result from stimulation of the senses. It is the use of sensory signals to represent objects and events that are identified, stored, and ultimately used for thought and action. It is a complex process that involves higher order mechanisms, including both top-down and bottom-up processing.

Question 2

Define Sensation. How is it related to perception?

Answer 2

Sensation: the elementary processes that occur at the beginning of the sensory system. It is the conversion of physical information into electrochemical signals in the brain and is the process that leads to perception. Without sensation, we would not be able to perceive the world around us.

Question 3

What the 7 stages of the perceptual process?

Answer 3

1. Stimulus in the environment: we encounter a stimulus outside our our body and attend to it
2. Stimulus hits our receptors: the stimulus hits our receptors of the relevant sensory system(s).
3. Receptor Processes: the sensory receptors respond to the stimulus and convert it into electrical energy.
4. Neural Processing: neurons transmit and process (change) these electrical signals as they travel through the brain.
5. Perception: conscious awareness of the object
6. Recognition: knowing what the object is based on existing knowledge and frameworks
7. Action: responding to the object

Question 4

What is the difference between a proximal and distal stimulus?

Answer 4

Distal Stimuli: the stimulus that is outside the body, in the environment. E.g. a cat.

Proximal Stimuli: the stimulus that hits the receptors, what actually triggers perception. (e.g. light reflected off of the cat onto the retina.

Question 5

What is the Principle of Transformation? How does it relate to the second stage of the perceptual process?

Answer 5

The Principle of Transformation: stimuli and responses created by stimuli are transformed (changed) between the distal stimuli and perception. Often many times

e.g. the distal stimuli (a cat) becomes a proximal stimuli (light reflected off the cat onto the retina) becomes electrical signals (transduction).

Question 6

What are sensory receptors? What are their two main functions and what do they respond to in the different sensory systems?

Answer 6

Sensory receptors are specialized cells that respond to environmental stimuli. They have 2 main functions:

1. to transform environmental energy (e.g. light waves) into electrical energy.
2. to shape perception through how they respond to different properties of stimuli.

• Visual sensory receptors respond to light
• Audio Sensory Receptors respond to pressure changes in the air
• Touch Sensory receptors respond to pressure transmitted through the skin.
• Smell and Taste sensory receptors respond to chemicals entering through the nose and mouth.

Question 7

What is transduction?

Answer 7

Transduction: the transformation of environmental energy into electrical energy.

Question 8

Where is the Primary receiving area for the visual system, hearing system, and skin senses?

Answer 8

Visual System: the occipital lobe
Hearing: Temporal lobe
Skin Sense: Parietal Lobe

Question 9

What distinguishes the last three steps of the perceptual process from the previous 4?

Answer 9

The last three steps are interconnected, they feedback into each other and all revolve around behavioral responses.

Question 10

What is visual form agnosia?

Answer 10

Visual Form Agnosia: the inability to recognize perceived objects

Question 11

Define knowledge. Why is knowledge important for the perceptual process?

Answer 11

Knowledge is any information that the individual brings into the situation. Knowledge and experience combine to effect every step of the perceptual process.

Question 12

What are the 3 major components of the perceptual process and how do the 7 steps fit into these components.

Answer 12

1. Stimulus (distal and proximal, steps 1-2)
2. Physiology (receptors, neural processing, steps 3-4)
3. Behaviour (perception, recognition, action, steps 5-7)

Question 13

What is the oblique effect?

Answer 13

Oblique effect: we see vertical and horizontal lines better than lines orientated any other way.

Question 14

What is Psychophysics?

Answer 14

The study of the relationship between the phyiscal (stimuli) and the psychological (the behavioural response)

Question 15

What are thresholds in Psychophysics? What is an absolute threshold? A difference threshold?

Answer 15

Threshold: the measure of limits in the sensory system.
Absolute Threshold: the smallest stimulus level that can be detected.
Difference Threshold: the smallest difference between two stimuli that we can detect.

Question 16

What role did Gustav Fechner play in the field of Psychophysics?

Answer 16

He revolutionized the field of study by proposing we study the mind by measuring the relationship between changes in the physical (the body) and changes in the experience (the mind).

For example, increasing the intensity of light (the physical) changes a person’s perception of the brightness (the mind)

Question 17

How does the Method of Limits work?

What are some limitations to this method?

Answer 17

The experimenter presents the stimulus in varying intensity in either ascending or descending order. The cross over value is the point between the lowest intensity they could detect and the highest intensity they could not. The absolute threshold is then calculated by averaging a series of cross over values.

Problems with this method: you are always presenting the stimuli in order which leads to:
- Anticipation: Saying yes when you are not perceiving the stimuli because you expect to see the stimuli

• Habituation: saying no when are you are actually perceiving the stimuli because you think that is what you did in the previous trial, you are used to saying no at that point of the trial.

Question 18

How does the Method of Constant Stimuli work?

What are limitations to this method?

Answer 18

The experimenter presents the stimulus in varying intensity in random order of intensities. after presenting each intensity multiple times, the threshold is calculated as the intensity that results in detection 50% of the time.

This method removes issues of habituation and anticipation but it takes longer.

Question 19

How does the Method of adjustment work?

What are limitations to this method?

Answer 19

The participant adjusts the stimuli intensity themselves until they can barely detect it. This is repeated and the threshold is calculated based on the an average.

Problems with this method: the stimuli is always presented in order AND the participant knows the intensity of the stimuli regardless of their perception. This leads to

• Anticipation: saying yes when you are not perceiving the stimuli because you expect to see it.
• Habituation: saying no when you are perceiving the stimuli because you are used to saying no at that point of the trial.

Habituation and anticipation are even more a of problem in the method of adjustment than they are in the method limits.

Question 20

What are 4 methods we use to measure perception above the threshold?

Answer 20

1. Magnitude Estimation: we assign value to stimuli at varying intensities based on their perceived magnitude
2. Recognition Testing: testing the participant’s ability to recognize a stimulus
3. Reaction time: measuring how fast we respond to stimuli
4. Phenomenological report: describing a stimulus, allows us to define perceptual stimuli we want to explain.

Question 21

What is Weber’s law?

Answer 21

The intensity required to detect the just noticeable difference (difference threshold) is proportional to the intensity of the original stimuli. The more intense the stimulus, the bigger the difference must be to detect a difference.