Unit 3 Topic 2 Psychology

What is perception?

An active process where the brain creates meaning from sensory information

What are the three stages of perception?

• Selection

• Organisation

• Interpretation

What is selection in perception?

Filtering out unimportant information to focus on relevant stimuli

What role does the thalamus play in selection (perception)?

Acts as a relay station (expect smell), filtering irrelevant stimuli and directing sensory information to primary sensory cortices

What is organisaiton in perception?

Grouping sensory information into a coherent pattern

What is interpretation in perception?

Assigning meaning to sensory input based on prior knowledge, expectations, motives, and emotions

What is sensation?

Detecting physical stimuli (energy) from the environment

What are the three stages of sensation?

• Reception

• Transduction

• Transmission

What is reception in sensation?

Sensory organs detect external stimuli using specilaised receptors

What is absolute threshold?

The minimum stimulus energy needed to perceive a stimulus 50% of the time under ideal conditions

What is transduction in sensation?

Receptors convert stimulus energy into an electrochemical signal (nerve impulse)

What is transmission in sensation? 

Nerve impulses are sent to the central nervous system for processing

What type of energy does our eyes detect?

Light - electromagnetic radiation that travels in waves

What does amplitude determine in light?

Brightness; higher amplitude = brighter appearance

What does wavelength determine in light?

• Colour;

• short wavelengths = blue/violate

• long wavelengths = red

What photoreceptors are found in the retina?

Rods and cones

What do rods detect?

Black, white, grey; work in low light; low detail

What do cones detect?

Colour vision, fine detail (high visual acuity), best in bright light

What is transduction in vision?

Conversion of light energy into electrochemical signals

How do photoreceptors send signals?

Photoreceptors → bipolar cells → ganglion cells

What is a ganglion cell’s receptive field?

The area of visual space the cell responds to

What forms the optic nerve?

Axons of ganglion cells

How does visual information leave the eye?

Via the optic nerves from each retina

What happens at the optic chiasm?

• half of the fibres cross:

  • left visual field → right hemisphere

  • right visual field → left hemisphere

Where does visual information go after the optic chiasm?

Thalamus → occipital lobes (primary visual cortex)

What role does the thalamus play in visual selection?

Filters irrelevant visual stimuli before sending information to the cortex

What happens in the primary visual cortex?

Image is broken up by feature detectors

Where are feature detectors found?

In the optic nerve and primary visual cortex

What is organisation in visual perception?

The brain arranges and assembles visual information into meaningful patterns using perception principles

What is interpretation in visual perception?

Assigning meaning to the visual stimulus

Which brain region identifies visual stimuli?

The temporal lobes compare incoming information with stored memories

What is sound?

A form of physical energy created by vibrating objects and transmitted as a wave through a medium

What are the key characteristics of sound waves?

• Amplitude

• Wavelength

• Frequency

What is amplitude in sound?

Maximum displacement of particles from their resting position

What causes amplitude to increase?

Greater applied force → larger amplitude

What is wavelength in sound?

Distance between two consecutive peaks or troughs

How is wavelength related to frequency?

Inversely related; high frequency = shorter wavelength

What is frequency measured in?

Hertz (Hz) - cycles per second

What does frequency represent?

Number of wave cycles per second

What is the role of the ear in reception?

Transforms vibrations into signals the brain can interpret

What does the outer ear do?

Collects and magnifies sound

What does the middle ear do?

Converts air vibrations into movement of tiny bones

What does the inner ear do?

Site of transduction

How do sound waves reach the eardrum?

Collected by the pinna → travel through auditory canal → vibrate the eardrum

Where does transduction occur in hearing?

In the cochlea

How is sound converted into electrical signals?

Fluid movement bends hair cells on the basilar membrane → bending generates electrical signals

Which nerve carries auditory signals to the brain?

The auditory nerve

How is auditory information transmitted to the brain?

From cochlea → auditory nerve → brainstem → thalamus

What responds to specific sound features?

Specalised neurons similar to visual feature detectors

How does the brain determine the source of a sound?

By using auditory cues (timing, intensity differenes)

What is the Mondegreen effect?

A hearing illusion where words or phrases are misheard or misinterpreted

What is bottom-up processing?

Building perceptions from raw sensory data by combining individual parts into a whole

What drives bottom-up processing?

Sensory information from the environment; stimulus-driven

Where does bottom-up processing begin in the brain?

In the primary sensory cortex, then moves to the association cortex

What is top-down processing?

Perception influenced by prior knowledge, expectations, and context

How does top-down processing assign meaning?

Integrates information from memory to interpret stimuli

What is a perceptual set?

A mental framework that shapes how we interpret sensory information

How can perceptual set affect perception?

Helps focus on relevant information but can create bias

How do past experiences influence perception?

Prior knowledge shapes how we interpret new stimuli

What is context in perception?

The environment in which a stimulus is observed; affects expectations

Which study demonstrates context effects in perception?

Bruner & Minturn (1955) - ambiguous figure interpreted differently depending on surrounding context

How does motivation influence perception?

Drives attention toward stimuli that help satisfy needs or desires

How does emotion bias affect perception?

Heightens sensitivity to stimuli that match our emotional state or expectations

What is the core idea of Gestalt psychology?

“The whole is greater than the sum of its parts”

When are Gestalt principles applied?

During the organisation stage of perception to convert sensory information into meaningful patterns

What is figure-ground organisation?

Distinguishing a central object (figure) from its background (ground)

How does camouflage use figure-ground?

By blending contours or reducing contrast to make the figure harder to separate from the background

What is closure?

The brain’s tendency to fill in gaps in incomplete images

What is continuity?

The tendency to perceive elements that follow a straight or curved path as continuous

What is similarity?

Grouping elements that look alike as belonging together

What is proximity?

Grouping elements that are close together

What is symmetry in perception?

Perceiving balanced arrangements around a central axis as unified

What are perceptual constancies?

Mechanisms that allow stable perception despite changes in the retinal image

What is size constancy?

Perceiving an object’s size as constant even when distance changes

What is shape constancy?

Perceiving an object’s shape as unchanged despite changes in viewing angle

What is colour constancy?

Perceiving an object’s colour as stable under different lighting conditions

What is depth perception?

Judging three-dimensional space and distance using environmental cues

What are the two types of depth cues?

Binocular and monocular cues

What is retinal disparity?

Each eye receives a slightly different image due to being 6-7 cm apart; the brain compares differences to perceive depth

What does larger disparity indicate?

The object is closer

What is convergence?

Eyes rotate inward to maintain focus as on object moves closer

What are monocular cues?

Depth cues requiring only one eye

What are the two types of monocular cues?

Accommodation and pictorial cues

What is accommodation in depth perception?

Lens changes shape (bulges/flattens) to focus light on the retina; controlled by ciliary muscles

What is linear perspective?

Parallel lines appear to converge with distance; used by artists to create depth

What is interposition?

When one object blocks another, the blocked object is perceived as further away

What is texture gradient?

Textures appear finer and less detailed as they recede into the distance

What is relative size?

Larger retinal image = nearer object; smaller = further away

What is height in the visual field?

Objects positioned closer to the horizon are perceived as more distant

What factors influence how we organise auditory information?

Amplitude, frequency, and the brain’s interpretation of sound

What is loudness?

Perception of a sound’s volume or intensity, directly related to amplitude

How is sound intensity measured?

In decibels (dB)

What is pitch?

Perceived highness or lowness of a sound, determined by frequency

How does frequency affect pitch?

Higher frequency → higher pitch; lower frequency → lower pitch

What is place theory?

Specific places on the basilar membrane vibrate for specific frequencies

How does the brain interpret pitch according to place theory?

By identifying which hair cells were activated

What is frequency theory?

Pitch is determined by the rate at which the entire basilar membrane vibrates

Who proposed frequency theory?

William Rutherford (1886)

What is the limitation of frequency theory?

Neurons cannot fire fast enough to match frequencies above ~1,000 Hz due to the refractory period.

What is timbre?

The unique quality of character of a sound that allows us to distinguish between sources with the same pitch and loudness