Cognitive Psychology

Sensation vs Perception

Sensation: Occurs when sensory receptor cells are stimulated and send information to specialised brain regions for processing.

Perception: The process of selecting, organising, and interpreting sensory information to give it meaning.

Key idea: Sensation provides the raw information; perception gives that information meaning.

Sensation ≠ Perception

McGurk Effect: Demonstrates that what we perceive is not always the same as the sensory information received.

Failure of Sensation

Congenital cataracts

• Light cannot properly enter the eye.

• Visual input is unavailable.

• Higher-level visual processing cannot develop normally.

Failure of Perception

Prosopagnosia (Face Blindness)

• Usually caused by damage to parts of the temporal lobe.

• Vision remains intact.

• Individual can see faces but cannot recognise them.

Vision as a Sensory System

Vision uses specialised receptor cells in the eyes to convert electromagnetic energy (light) into neural signals.

Key facts:

• One of the most studied areas in cognitive psychology and neuroscience.

• Around 25% of the brain's metabolic energy is involved in visual processing.

Transduction

Transduction: The conversion of one form of energy into another.

In vision:

• Light enters the eye.

• Photoreceptors convert light energy into electrical signals.

• These signals are transmitted through the nervous system.

Parallel Processing

The brain processes visual information simultaneously rather than one step at a time.

Although neural impulses are relatively slow, the brain compensates through parallel processing.

Different aspects of a scene are analysed simultaneously:

• Colour

• Depth

• Movement

• Shape

Basic visual pathway:
Retina → LGN (Lateral Geniculate Nucleus) → V1 (Primary Visual Cortex)

Visual Pathways

Parvocellular Pathway ("P")

Processes:

• Fine detail

• Colour

• Slow movement

Magnocellular Pathway ("M")

Processes:

• Motion

• Flicker

• Broad/global features

• Little or no colour information

Feature Detection

Visual neurons respond to specific features within their receptive fields.

Receptive field: The area of the visual field to which a neuron responds.

Neurons in the visual cortex detect:

• Edges

• Lines

• Angles

• Orientation

Higher-level visual processing is built from information supplied by lower-level neurons.

Models of Visual Processing

Hierarchical Models

Information flows through a sequence of increasingly complex stages:

Primary Visual Cortex → Secondary Visual Cortex → Temporal/Parietal Regions → Frontal Regions

Non-Hierarchical Models

Visual processing is more complex than a simple chain.

Features include:

• Back-projections (higher areas influence earlier areas)

• Information can bypass some processing stages

• Visual information may reach higher-order regions directly

Two Visual Streams

Ventral Stream ("Vision for Perception")

Location: Inferotemporal cortex

Functions:

• Object recognition

• Object identification

• Conscious visual perception

Characteristics:

• Object-based processing

• Answers: "What am I looking at?"

Dorsal Stream ("Vision for Action")

Location: Posterior parietal cortex

Functions:

• Guiding movements

• Reaching

• Grasping

• Spatial awareness

Characteristics:

• Viewer-based processing

• Largely automatic

• Answers: "How do I interact with it?"

Evidence for Separate Visual Streams

Visual Form Agnosia (Ventral Stream Damage)

Symptoms:

• Cannot recognise object forms.

• Colour and texture perception remain intact.

• Difficulty identifying objects.

Preserved ability:

• Visually guided actions remain relatively normal.

Optic Ataxia (Dorsal Stream Damage)

Symptoms:

• Difficulty reaching for or grasping objects.

• Poor visually guided movements.

Preserved ability:

• Object recognition remains relatively normal.

Ambiguous Figures

Bi-stable perceptions:

• Two interpretations are possible.

• Only one interpretation can be perceived at a time.

Demonstrates that:

• Conscious perception is selective.

• Perception is actively constructed by the brain.

Perceptual Organisation

To create meaningful perceptions, the brain must organise sensory information.

Objects must be perceived as distinct from their surroundings (Gestalt).

Four Major Types of Perceptual Organisation

1. Form Perception

Based on Gestalt Principles:

Proximity: Objects close together are grouped together.

Similarity: Similar objects are grouped together.

Closure: Missing information is mentally filled in.

Figure-Ground: Objects are separated from their background.

2. Depth Perception

Allows perception of a three-dimensional world.

Uses:

• Monocular cues (one eye)

• Binocular cues (both eyes)

3. Motion Perception

Allows detection and interpretation of movement.

4. Perceptual Constancy

Objects are perceived as stable despite changing sensory input.

Examples:

• Size constancy

• Shape constancy

• Colour constancy

Bottom-Up vs Top-Down Processing

Bottom-Up Processing

Sensation → Perception

Processing begins at sensory receptors.

Sequence:

1. Detect features.

2. Analyse information.

3. Organise information.

4. Create perception.

Data-driven processing.

Top-Down Processing

Perception → Sensation

Processing begins with:

• Expectations

• Knowledge

• Experience

• Context

The brain forms hypotheses and compares incoming information against them.

Concept-driven processing.

Factors Influencing Perception

Perception is influenced by:

Attention

• What we focus on receives greater processing.

Arousal

• Alertness affects how information is perceived.

Emotions

• Emotional states can alter interpretation of sensory information.

Quick Exam Summary

Memory and Learning

Memory: A set of systems that store and retrieve information acquired through the senses.

Learning: Changes in physiology or behaviour that occur as a result of experience.

Memory involves: The ability to store, recall, and recognise information, events, and experiences.

Memory models are often described in terms of:

• Capacity (how much information can be stored)

• Duration (how long information can be stored)

Information Processing Model of Memory

Memory consists of three main processes:

Encoding → Storage → Retrieval

Encoding

The process of converting incoming information into a form that can be stored.

Includes:

Acquisition: Registration of information in temporary sensory storage.

Consolidation: Strengthening and stabilising memory traces over time.

Storage

The maintenance of information in memory over time.

Retrieval

The process of recovering stored information and bringing it into conscious awareness or using it to guide behaviour.

Standard Memory Model (Atkinson & Shiffrin, 1968)

Three memory stores:

Sensory Memory → Short-Term Memory (STM) → Long-Term Memory (LTM)

Sensory Memory

A brief sensory-based representation of incoming information.

Types:

• Iconic memory: Visual information

• Echoic memory: Auditory information

Characteristics:

• Very brief duration (milliseconds to a few seconds)

• Large capacity

• Information rapidly decays unless attended to

Short-Term Memory (STM)

Temporary storage for information currently in awareness.

Characteristics:

• Limited capacity

• Limited duration

Capacity

Miller (1956):

• Approximately 7 ± 2 items

• Typical range: 5–9 items

Duration

Without rehearsal:

• Lasts approximately 20–30 seconds

With rehearsal:

• Duration can be extended

Long-Term Memory (LTM)

Permanent memory store.

Characteristics:

• Very large (effectively unlimited) capacity

• Potentially lifelong duration

Retrieval

Information is recovered from LTM and brought into working memory/STM for conscious use.

Working Memory Model (Baddeley & Hitch)

Working memory replaced the simple concept of STM.

It consists of several interacting components:

• Central Executive

• Phonological Loop

• Visuospatial Sketchpad

• Episodic Buffer

Phonological Loop

Temporary storage and rehearsal of verbal and auditory information.

Uses sound-based coding.

Capacity: Approximately the amount of information that can be rehearsed in 1.5–2 seconds.

Evidence: Word-Length Effect

Short words are recalled more easily than long words.

Example:

• 5 monosyllabic words recalled better than 5 polysyllabic words.

Functions:

• Language learning

• Vocabulary acquisition

• Speech comprehension

People with impaired phonological working memory often struggle to learn new words.

Visuospatial Sketchpad

Temporary storage and manipulation of visual and spatial information.

Used for:

• Faces

• Objects

• Written words

• Mental imagery

Examples:

• Mental rotation tasks

• Visual mnemonics

• Mental arithmetic

Operates independently of the phonological loop.

Central Executive

The attentional control system of working memory.

Not a memory store.

Functions:

• Directs attention

• Coordinates other working memory systems

• Links working memory with long-term memory

Episodic Buffer

Acts as a temporary backup store.

Functions:

• Integrates information from different sources

• Connects working memory and long-term memory

• Creates coherent conscious experiences

Long-Term Memory Types

Two major ways of classifying LTM:

By Storage

• Declarative Memory

• Procedural Memory

By Retrieval

• Explicit Memory

• Implicit Memory

Declarative Memory (Explicit Memory)

Memory for facts and events that can be consciously recalled.

Episodic Memory

Memory for personal experiences and events.

Examples:

• Your first day at university

• A birthday party

• Childhood memories

Also called autobiographical memory.

Semantic Memory

Memory for general knowledge and facts.

Examples:

• Melbourne is the capital of Victoria.

• Water freezes at 0°C.

Does not include memory of when the information was learned.

Procedural Memory (Implicit Memory)

Memory for skills and actions.

Examples:

• Riding a bicycle

• Driving a car

• Reading

Knowledge is expressed through performance rather than conscious recall.

Other Forms of Implicit Memory

Priming

Exposure to a stimulus influences later responses to that stimulus.

Example:

• Seeing a word earlier makes it easier to recognise later.

Classical Conditioning

Learning associations between stimuli.

Example:

• A neutral stimulus becomes associated with a meaningful stimulus.

Habituation

Learning to ignore unimportant stimuli.

Example:

• Tuning out background noise.

Sensitisation

Learning to pay increased attention to potentially important or threatening stimuli.

Explicit vs Implicit Retrieval

Explicit Memory

• Conscious retrieval

• Intentional recall

Examples:

• Recalling a fact

• Remembering a past event

Implicit Memory

• Influences behaviour automatically

• Does not require conscious awareness

Examples:

• Riding a bike

• Priming effects

Declarative vs Procedural Memory

Declarative: Things you know and can explain to others.

Procedural: Things you know how to do and can demonstrate through action.

Where Are Memories Stored?

There is no single memory centre in the brain.

Memory involves multiple brain regions.

Hippocampus

Critical for:

• Forming new declarative memories

• Retrieving episodic memories

Prefrontal Cortex

Important for:

• Memory retrieval

• Organising remembered information

Left frontal cortex: More involved in semantic memory.

Right frontal cortex: More involved in episodic memory.

Amygdala

Processes emotional aspects of memory.

Emotionally significant events are often remembered more strongly.

Sensory Cortices

Visual, auditory, and other sensory areas contribute components of stored memories.

Eyewitness Testimony

Eyewitness evidence is important in the legal system but is not always reliable.

Factors affecting accuracy:

Emotional Arousal Theory

High stress and anxiety can distort memory.

Suggestibility

Leading questions can alter recollections.

Contextual Factors

Examples:

• Poor lighting

• Distance from the perpetrator

• Brief exposure time

Reconstructive Memory Theory

Memories are reconstructed each time they are recalled.

Repeated retelling can unintentionally change details of the original memory.

Amnesia

Memory impairment caused by:

• Brain injury

• Disease

• Drug abuse

• Psychological trauma

Retrograde Amnesia

Loss of memories formed before injury or illness.

Characteristics:

• Difficulty remembering past events

• Loss of previously learned information

Anterograde Amnesia

Inability to form new conscious memories after injury.

Characteristics:

• Difficulty learning new information

• Older memories often remain intact

Quick Exam Summary