Chapter 8 - Perception

Perception

The process of selecting, organising and interpreting information to make sense of the world.

Attention

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

Sustained Attention

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

Divided Attention

The ability to distribute our attention so that two or more activities may be performed simultaneously (multitasking). The more complex the task = more difficult to split attention. E.g Eating dinner while watching tv.

Selective Attention

Involves choosing and attending to a specific stimulus whilst at the same time excluding other stimuli. Distractions can be internal or external. E.g Studying in a noisy room and filtering out distracting sounds.

Influences on our attention

If a stimulus is of personal importance, we are more likely to notice and attend to it.

Cocktail Party Phenomenon

When your attention becomes selective when hearing your name in another conversation.

Physiological State

If hungry/thirsty are more likely to pay attention to things or places where food/water is available.

Motives

Motivated people are more likely to pay attention.

Past Experiences

More likely to notice things connecting to you.

Changes in stimuli that can attract our attention

Movement, contrast, intensity, size, and duration/repetition - too much repetition = ‘used to it’ (habituation).

Stages in Perception

S-O-I - Selection, Organisation, Interpretation

Selection

Filtering information

Multiple psychological processes selecting features of stimuli and organising them into a meaningful pattern. Cannot process all information received, leading to paying attention to the most important information.

Organisation

Creating a whole

The grouping of elements or features of a stimuli to form a whole to be given meaning. Occipital lobe puts the information that has been broken down, back together.

Interpretation

Understanding Stimuli

The process in which incoming sensory information is given meaning so it can be understood. It allows us to understand what we a sensing. Usually happens when stimuli is vague, confusing or ambiguous that we become aware of the process.

Top-Down Processing

Type of processing used when stimuli is relatively familiar and less complex. Goes from broad information to specific. Driven by prior knowledge and expectations (schemas).

Bottom-Up Processing

Type of processing used when information is unfamiliar or highly complex. Goes from specific to broad information. Is entirely based on the way information is stored in the individual brain.

Cornea

A transparent, curved layer that protects the eye and focuses light.

Pupil

A black circle in the middle of the eye controlling the amount of light entering.

Iris

The coloured part of the eye where muscles expand and contract t allow more or less light into the eye.

Lens

A transparent flexible layer that mainly focuses light.

Retina

Receives and absorbs the light entering the eyeball and processes images.

Optic Nerve

Takes all the information from the retina to the primary visual cortex.

Blind Spot

No photo receptors on small part of the retina.

Photo Receptors

Light sensitive visual receptors.

Cones

Shows colour, responds to high levels of light.

Rods

Shows black, white, and shades of grey. Responds to low levels of light.

Vision Process

Stimulus energy enters the eye (light electromagnetic energy).

Reception

Receptors in the eye detect and respond to light.

Transduction

Light is converted from electromagnetic energy to energy in the form of action potentials (neural impulses).

Transmission

Sent to the brain via the optic nerve.

Interpretation

Interprets the information sent to the primary visual cortex.

Biological Factors of Perception

Binocular, monocular, individual physiological make-up, ageing, genetics, depth cues.

Social Factors of Perception

Culture.

Psychological Factors of Perception

Gestalt principles, perceptual set, context, motivation, past experiences/memory.

Individual Physiological Make-Up

If malformation of our visual system occurs during development, we will experience visual impairment.

Ageing

As we get older our eyes change.

Around the middle age stages, our lenses become less elastic, meaning we struggle to focus on objects at close range.

Cells may clump, causing specks or tiny spots to drift across the field of vision.

Genetics

Eye diseases, such as congenital cataracts, retinal degeneration, and eye malformations, have been shown to have genetic links.

Depth Cues

Depth perception and Depth cues

Depth Perception

The ability to see a 3D space an accurately estimate the distance of objects

Depth Cues

Sources of information from the environment (external) or from within the body (internal) that assist perception of how far away objects are.

Binocular Cues

Requires both eyes to work together to provide the brain with information about depth and distance.

Retinal disparity and Convergence

Retinal Disparity

Refers to discrepancies between an image that reaches the left and right eye. More difference between the images, the closer the object is.

Convergence

Eyes simultaneously turning inwards as an object moves closer. When these muscles relax/tense, they feed information the eye position to the brain to judge distance.

Monocular Cues

Contain information from one eye only. Consists of accommodation and pictorial cues.

Accommodation

Involves the automatic focusing of the lens in the eye to adjust shape in response to changes in the distance of view from an object.

Pictorial Cues

Create an impression of depth on a flat 2D surface where depth does not exist. They include linear perspective and relative size.

Linear Perspective

The apparent convergence of parallel lines creates the illusion of increasing distance.

Relative Size

The perception that the object that produces the largest image on the retina as being closer and the object that produces the smallest image as being further away, when objects are expected to be the same size.

Interposition (overlap)

When one object partially covers another object and is perceived as being in front of, and therefore closer than, the object it covers.

Texture Gradient

Refers to the surface features of an object being seen as smaller and less detailed the more distant the object becomes.

Height in Visual Field

Objects closer to the horizon are seen as being further away from us.

Psychological Factors

Perceptual set, past experiences, context, motivation, emotional state, and memory.

Perceptual Set (expectancy)

A readiness or predisposition to perceive stimuli in a particular way according to our expectations.

It affects which elements of stimuli we attend to + the way we organise it. Can sometimes lead to perceptual distortions/mistakes. Only notice the information consistent with our expectations. Factors affecting it may include personal characteristics, past experiences, motivation, emotional state, beliefs, and cultural backgrounds.

Past Experiences

Our prior exposure to stimuli and previous life experiences. It creates a tendency to interpret new stimuli in the same way as past stimuli.

Context

The information that surrounds a stimulus and contributes to perceptual set.

Motivation

Processes within us which activate behaviour that we direct towards achieving a particular goal. Can influence visual perception and can be influenced by psychological, biological, and social factors.

Emotional State

How an individual is feeling as a point in time. Can cause us to perceive information in a certain way that is consistent with the feeling experienced.

Memory

What is stored in long-term memory is used to identify, interpret, and understand the meaning of new information. It also influences all other psychological factors that affect visual perception.