Chapter 8 and 9

psychology

Define sensation

Detecting Raw data through sensory receptors

Perception

Incoming sensory information is interpreted and given meaning. We are only aware of information once it is perceived.

List the senses

Vision, taste, hearing, smell, touch, pain and kinaesthesia, which is body position and movements.

How does physical stimuli get interpreted?

Information is formed into a specific type of energy that stimulates sensory receptor cells.

Can sensory information (stimuli) be external or internal?

Stimuli can be both external and internal

What is attention

The process of focusing on specific stimuli or aspects of the sensory environment whilst ignoring and therefore excluding others

3 types of attention

Sustained attention

Divided attention

Selective attention

What is sustained attention and example

Involves maintenance of attention on a specific stimulus or task for a continuous period of time without being distracted
E.g: Listening to a teacher.

Challenges of sustained attention

Can be difficult to maintain sustained attention for significant amount of time

What is divided attention & example

The ability to distribute our attention so that two or more activities may be performed simultaneously.
E.g: eating dinner while watching a movie

Is divided attention and shifting attention the same?

No, shifting attention is when we change our focus from one task to another whilst divided attention is distributing attention so 2+ activities can be performed simultaneously.

What is selective attention and example

Involves choosing and attending to a specific stimulus while at the same time excluding other stimulus.
E.g: studying in a noisy room

What is beneficial about selective attention?

Enable you to maintain a task in the presence of distracting stimuli.

Factors affecting attention

Personal importance

Physiological state

Past experience

Motives

Novel stimulus

PPPMN

Roles of attention:

Filters distracting stimuli to maintain concentration

Supports adaptation in environment

Enables conscious awareness of stimuli

Functions as a state of readiness

Supports learning, memory and other cognitive processes

Enables us to complete tasks without distraction

Is perception an active or passive process?

Active process, resulting from brain activity that constructs personal understanding of reality from raw sensory information, allowing us to adapt to our environment.

Top-down processing:

The perceptual process starts at the top with higher level processing in the brain and then works down from the whole to the details.

Guided by: past experiences, knowledge and expectations, and context is important

Bottom-up processing AKA: data-driven processing

The perceptual process starts at the bottom with raw sensory information progressively analysed and sent up to the brain for higher level mental processing.
Relies entirely on sensory data, with initially no prior knowledge or higher level cognitive processes required.

Why is top down processing useful?

Allows perception of incomplete stimuli, by inferring missing details. 

Psychological factors of visual perception

Gestalt principles

perceptual set

context

motivation

past experiences

memory

Biological factors of visual perception

• binocular depth cues:

- convergence
- retinal disparity

• Monocular depth cues

- accommodation

- linear perspective

- interposition

- texture gradient

- Relative size

- height in the visual field. 

Social factors influencing visual perception

Culture

Depth perception

The ability to accurately estimate the distance of objects and therefore perceive the world in three dimensions.

Depth cues

The principles our brain has learned from experience with the external world, relating to the interpretation of an object’s distance in the visual field.

2 kinds of depth perception and depth cues

Binocular - requiring two eyes to operate
Monocular - requiring only one eye to operate

Binocular Depth cues

Requires the use of both eyes working together to provide information to the brain about depth and distance.

List the binocular depth cues

Retinal disparity
Convergence

Convergance

Involves the brain detecting and interpreting depth/distance from changes in the tension in the eye muscles when they turn inwards to focus on close objects.

Retinal Disparity

Refers to the very slight difference in the location of the images on the retinas, which enables us to make judgments about the depth or distance of an object. After 10 metres the difference is minimal.

Monocular depth cues

Requires only one eye, but also operate with both eyes. Most depth cues are monocular, so many daily activities can occur without difficulty if vision is lost in one eye.

Monocular cues

Accommodation
pictorial cues:
T texture gradient
H height in the visual field
R relative size
I interpostion
L linear perspective

What is accommodation?

The automatic adjustment of the shape of the lens to focus an object in response to changes in how far away the object is.

Pictorial depth cues list them:

T  Texture gradient

H  Height in the visual field

R  Relative size

I     Interposition

L  Linear perspective

Pictorial depth cues

Depth cues used by artists to create a 3D perception of something that exists on a 2D surface.

Linear perspective

Is the apparent convergance of actual/imagined parallel lines as they recede into the distance

Interposition

Occurs when one object partially blocks or covers another, and the partially blocked object is perceived as further away than the object that obscures it.

Texture gradient

Refers to the gradual reduction of the detail that occurs in an object or surface as it recedes into the distance, compared with an object or surface that is close and perceived in fine detail.

Perceived objects:
With fine detail and clear as being closer
With less detail, as being further away.

Relative size

Is the tendency to visually perceive objects that make the largest image on the retina as being closer, and the object that produces the smallest image on the retina as being further away.
The objects must be expected to be about the same size in real life.

Height in the visual field

Refers to the location of objects in our field of vision.
With objects located closer to the horizon perceived as more distant than objects further from the horizon

Gestalt principles

Refers to a way to organise the parts/features of a visual stimulus by grouping them to perceive a whole. The ‘principles’ are applied to visual information to assist meaningful perceptions. The parts individually lack much meaning.

We tend to automatically group visual stimulus and do so in the simplest way possible.

List the gestalt principles

F- figure ground

P- proximity
C- closure

 S- similarity

Figure ground

Gestalt principle
Organise visual information by dividing visual stimulus into a ‘figure’ that stands out from the ‘ground; (surroundings). The figure is the centre of our focus.
To achieve this we interpret contour, the contour belongs to the figure and defines it against the background

What is contour

A part of gestalt principle figure ground. Contour is the imaginary line that separates an object from its background. The contour belongs to the figure and defines it against the ground.

Camouflage occurs…

When the figure and ground are not easily separated but blend together. Restricting the ability to separate the figure from the background

Figure ground importance.

It allows our perception to separate the stimulus from the background

Closure

Gestalt principle
Perceptual tendency to mentality ‘close up’, fill in or ignore gaps in visual stimulus and percieve incomplete objects as a complete.

Similarity

Gestalt principle
Tendency to perceive parts of a visual stimulus that have similar feaftures (size, shape, texture, colour) as belong together in a grope or ‘whole’

Proximity

Gestalt Principle aka Nearness
Tendency to perceive parts of visual image which are positioned close together as belonging together in a group

Psychological factors influencing Visual perception

perceptual set
context

motivation
past experience
memory

Perceptual set

psychological factor
Is a temporary readiness to perceive something in line with what we expect it to be. May also predispose us to perceive certain objects or events rather than others.

Context

Psychological factor
Refers to the setting or environment in which a perception is made.
Context has focusing role that enables quick and accurate interpretation.

Motivation

Psychological factor
refers to processes which activate and sustain purposeful, or goal directed behaviour.

Motives influenced by:
psychological factors (interests and desires esc)

Biological factors (such as bodily processes esc)
Social factors (influence of who we are with, money, our cultural background).

Past experience

Psychological factor:
refers to our personal experiences throughout our lives. This includes everything we have learned both intentionally and unintentionally.
Our visual perception relies heavily on past experience. 

Memory

Psychological Factor:

Memory is the process of storing and retrieving this perceived information for use when needed.

Visual perception and memory are closely interrelated, perceiving incoming visual information would be meaningless without the ability of recall and link to corresponding memories.

Top down processing would not be possible
bottom-up processing would provide inadequate information to visually perceive the world as we do. 

Culture

Social factor

Experience with or in a particular culture can influence the way we process and interpret visual information.

Social factors

Social factors involve influences from the external social environment in which we interact with others.

Distortion of perception

ch 9

A perceptual distortion

involves an inconsistency, or ‘mismatch’, between a perceptual experience and physical reality.

What do visual illusion demonstrate?

Visual illusions demonstrate cases in which reality is misperceived for no immediately apparent reason.

What is a visual illusion

A misperception of external visual stimuli because of a distortion or mistake when interpreting the stimuli. There is a mismatch between our perception and what we understand as physical reality.

Are Visual illusion effects avoidable?

Generally, the illusory effects are unavoidable. Even when we know that we are looking at an illusion and have an understanding of why the illusion occurs

what is the muller-lyer illusiom

Müller-Lyer illusion is a visual illusion in which one of two lines of equal length, each of which has opposite shaped ends, is incorrectly perceived as being longer than the other

Theories for how the muller-lyer illusion works

• using the wrong mental strategies when interpreting incoming visual stimuli.. Particularly, using depth and distance cues when judging 2D objects.

• Pas experience: contradicts what we know about physical reality

• Past experience: carpentered world hypothesis

Size constancy

Refers to the fact that we maintain a constant perception of an object’s size, even though the size of the image on the retina alters as the object moves nearer to or further from us.

Shape constancy

Refers to the fact that an object is perceived to maintain its known shape despite the changing perspective from which it is observed.

How does shape constancy relate to the Ames rooms.

In the Ames Room, shape constancy plays a key role in maintaining the illusion:

The brain assumes the room is a regular rectangular shape, because that's what it expects based on experience.

which leads us to interpret the distorted room as normal.

How does size constancy relate to the Ames rooms.

The two people cast very different-sized images on the retina. One person appears giant and the other looks tiny, despite being similar in size, because the brain incorrectly believes both people are equally distant, it doesn’t apply size constancy.

The Ames Room Illusion shows that we maintain

shape constancy (of a room) at the expense of size constancy

The spinner dancer illusion

is a visual illusion in which the silhouette of a female dancer can be interpreted as spinning clockwise or anti-clockwise.

Spinner dancer illusion, how it works

Because the lack of depth cues to distinguish between the front and back of the silhouette.

Agnosia

Is characterised by loss or impairment of the ability to recognise and identify objects, persons, sounds or other sensory stimuli using one or more of the senses despite otherwise normally functioning senses

Visual agnosia

 is the loss or impairment of the ability to recognise visual stimuli. This results in difficulty recognising familiar objects and possibly faces.
Not related to sight, loss of memory or language.

Apperceptive visual agnosia

An inability to accurately perceive visually presented stimuli. What is seen cannot be recognised.

Associative visual agnosia

An inability to relate visual stimulus with memory about objects stored in information despite otherwise normal perceptual abilities.

Prosopagnosia

An inability to recognise a familiar face, including their own when seen in a mirror or photograph.

Simultanagnosia

An inability to recognise more than one object at a time in a scene that contains more than object.

Topographical agnosia

An inability to find one’s way around familiar environments.

.Colour agnosia

An inability to identify and distinguish between different colours, despite normal basic colour vision and colour discrimination mechanisms.

Agnosic alexia

An inability to recognise or comprehend written or printed words

Causes of agnosia

Caused by drain damage affecting neural pathways. Less than 1% of people diagnosed with brain damage have agnosia.
suddenly:
Stroke
Traumatic brain injury
Gradually:
Tumour
overexposure to environmental toxin

Treatment of agnosia

No direct cure. Treatment of underlying issues is done when possible & rehabilitation is tailored to specific problems

Synaesthesia 

is a perceptual experience in which stimulation of one sense produces additional sensations in another

grapheme-colour synaesthesia

 in which a person sees colours when viewing letters, numbers or words.

Other types of synaesthesia include:

mirror–touch synaesthesia — a person watching another individual being touched feels a tactile sensation on their own body

auditory–tactile synaesthesia — certain sounds trigger sensations in parts of the body

word–gustatory synaesthesia — experiencing tastes when hearing certain words

pain synaesthesia — experiencing pain when observing or imagining another person in pain

chromesthesia — perception of nonvisual stimuli (e.g. sounds, tastes, odours) is accompanied by colour sensations

chromatic audition — colour sensations are experienced when sounds are heard

Time–space synaesthesia — individuals experience months, days, hours, and other units of time as occupying specific spatial locations around them (e.g. January is 30° to the left of my body).

•

What causes synaesthisia.

UNSURE Thought to be genetic or Neurological condition
Hyperexcitable sensory processing or lack of pruning in brain areas

Spatial neglect

neurological disorder, unable to notice anything on one side even though there may be no sensory loss. Tend to behave as if the side affected does not exist.