Lecture: Sense and Perception

Key Question Number 1:

How do we construct our representations of the external world?

• Psychophysics is the study of how we detect stimuli, determine its intensity and know when the stimuli has changed. For example: Absolute Thresholds have been determined for all the senses, JND, etc.
  
• Cognitive Psychology is the study of mental processes. It employs an information processing model to better understand how sensations (inputs) enter the system. This model implies that sensation and perception are very active mental processes.
  
  

These two studies concentrate on two important processes:

Bottom-up processing which focuses on how information enters our sensory systems.
Sensory Receptors > Brain > Perception

Top-down processing which focus on how experience and expectation combine with sensory information to construct a picture of the outside world.

Expectations and context> Brain> Sensory receptors

Top-down processing is seen the influence of perceptual sets i.e. a readiness to interpret stimuli in a specific way on the basis of expectations, experiences or psychological states.

• New Understandings of Sensation and Perception
  
  You are well adapted to obtain the information that is vital for your survival. For example, you can screen out the repetitious sensations to free you to be more aware of a novel stimulus.
• You are designed to detect changes in your environment.
• You are capable of sensory adaptation i.e. the ability to readjust ou sensory and perceptual worlds.
• Much of the work of the brain is done automatically and without our awareness.
• Your brain employs parallel processing. You have neural teams that process information at the same time.
• You construct a view of the world that resides in your brain. You make choices in the way that you interpret sensory information.
• You can conjure up sights and sounds within our brain without external stimulus.
• While you sense stimuli, you perceive objects and events.
• Perception is effortless, integrated and multimodal.
• Perception = Sensory input + cognition. In other words, it is both physical and psychological.
• Perception is active, directed and produces a constant interplay between perception and behavior.

Key QuestionNumber 2

How do perceptual processes allow use to select, organize and interpret sensation so that we can construct our mental representations of the world?

Think of each of the senses, what do we want to know?
Sight?
Hearing?
Taste?
Touch?
Smell?

Key Aspects of Perception

SELECTIVE ATTENTION

• you focus on a limited aspect of all you are capable of experiencing
• you give our undivided attention but the unattended stimuli can still have an effect (the cocktail party effect)

ORGANIZATION OF STIMULI

A gestalt or form

1. you are designed to look for meaning and find form in sensory information
2. the whole may exceed the sum of the parts
3. you combine bottom up and top down processing to organise sensory informaton and make sense of it

Steps in Perception
We must first complete a number of steps before we can make sense of our sensations
1) distinguish the object from the background
2) distinguish its form
3) discern its distance from us and its motion

Form Perception helps us perceive shapes and involves a number of principles.
Depth Perception helps you know how far way an object is from you land to do this you employ both Monocular Cues and Binocular Cues.
Perceptual Constancy this process allows us to perceive an object as constant even though the stimuli we receive changes.

Interpretation.

• Psychologist seek to determine the role of learning and experience in perception.


• It is argued that there are critical periods in our perceptual development when windows of opportunity open to allow use to develop our perceptual process. (Blakemore and Cooper Cat experiment)


• Subjective Contours shows us that the brain will fill in information to make better sense of the world.

We perceive the world not exactly as it is, but as it is useful for use to perceive it. Each of us might see the world in very different ways. Our realities are individual.