Intro to psych - Week 3

Sense and perception

Synesthesia

Signals from various sensory organs are processed differently, and sometimes get crossed, creating different sensations

Which cortex controls taste?

Gustatory

Which cortex controls smell?

Olfactory

McGurk effect

Illusion which what we sees overrides what we hear. As the brain combines visual information with the auditory information, causing it actively construct something new.

Transduction

Converting outside stimuli (sound waves, visual information etc) into electrical signals that become neural activity

SENSATION VS PERCEPTION

Sensation = Process that information of the external world enters through the brain through stimulation of sense organs

Perception = What the brain interprets and makes sense of the information

HABITUATION VS SENSORY ADAPTATION

Habituation = Tendency of the brain to stop attending to constant information → e.g. filtering out information like background noise while studying

Sensory adaptation  = When receptor cells become less responsive to unchanging stimulation due to adaptation (at the level of sensation) → e.g. swimming in cold water, after a while it doesn’t feel cold anymore

Absolute threshold

the lowest level of a physical stimulus that a person can detect 50% of the time

Difference threshold/just noticeable difference

the smallest change in a physical stimulus that a person can detect 50% of the time

Weber’s Law

Size of the difference threshold is proportional to the intensity of of the stimulus

Parts of the eye and their functions

Vitreous humour = Nourishes eye, give shape

Aqueous humour = Clear liquid that nourishes eye too

Retina = Photoreceptor cells here, which gather information from light waves, converting it into nerve impulses

• Rods: Helping us see in low light levels 

  • (peripheral of retina)

• Cones = Sensory receptors, mostly located in fovea (centre of retina), which is responsible for colour and sharpness of vision (operate best in well lit conditions, helping to see colours)

• Bipolar cells: Rods and cones processed by them

• Ganglion cells: Rods and cones processed by them, which then sends electrical signals to the optic nerve

  • There is a gap between the optic nerve where if stimuli hits it, it won’t process → BLIND SPOT

  • But we have two eyes, which helps to fill in missing stimuli

Fovea = Densely packed with photoreceptors, helping to focus the information

Iris = Coloured area containing muscles that control pupils

Pupils = Opening in the centre of the iris that changes

How does the brain process visual information through the eye?

• Light enters, stimulating rods and cones stimulates bipolar cells, which stimulates the nerves to then carry on information to the brain, allowing the brain to then process into an active image

• Can see things because of LIGHT WAVES

  • Visual system sensitive to 400-700 nanometers

Light waves

Amplitude —> Brightness

Wavelength —> Colour/hue

Purity of wavelength —> Saturation

Colour perception theories

1) Trichromatic (3 colours) theory

2) Opponent processing theory

Trichromatic (3 colours) theory

• Propose that we have 3 types of cones: blue, green, red

• All colours can then be mixed using these main 3 colours, but we use signals mixing to form the different colours 

  • E.g. red and blue signals stimulate cones that causes our brain to perceive purple

Opponent processing theory

• Proposes 4 primary colours arranged in opponent pairs beyond the cones, so we can’t perceive certain colour combinations, we can only process one at a time, as processing one colour means we can’t process the other

• E.g. if we try to process blue and yellow at the same time it will only appear as gray

Different types of colour-blindness

Monochromatic vision = Condition where two or three cones don’t work properly as the result of genetic mutations

Dichromatic vision = Condition in which one cone does not work properly, with resulting colours being determined by the combination of only two cones

Soundwaves

Amplitude = Loudness

Frequency = Pitch

Complexity = Timbre (sound texture → e.g. difference between violin and trumpet)

What is the ear made up of?

Outer ear, middle ear, inner ear

Outer ear

Pina, ear canal, ear drum

Middle ear

Hammer, anvil, stirrup

Inner ear

Oval window, cochlea, auditory nerve, vestibular organ (has semicircular canal which helps with balance)

How are sound waves transmitted into the brain?

Sound waves enter the ear through the ear canal → Ear drums vibrate → Causes hammer, anvil, and stirrup to also vibrate which amplifies sound → Vibration transmitted into oval window (in the inner ear ) to the cochlea, which is filled with fluid that also vibrates → Hair cells that make up the corti resting on the basilar membrane are bent by waves in the fluid → Sends the vibrations to the auditory nerves

Hearing theories

Place theory, frequency theory

Place theory

there are different pitches which are experienced by stimulation of hair cells in different locations on organ of corti

Frequency theory

Pitch is related to the speed of vibrations in the basilar membrane

Transduction process in nose?

Olfaction

Olfaction

Physical process of detection of odour molecules leading to the psychological phenomenon of smell

Label the parts of the olfactory bulb

Olfactory bulb = Just below frontal lobe, which receives information from the olfactory receptor cells

Where do the signals from the olfactory bulb go?

Olfactory bulb → Primary olfactory cortex  and amygdala (Emotional processing of smells)

Transduction of taste

Gustation = Chemically based physical process that leads to the sensation of taste

What is the neural pathway of taste?

Taste bud —> Thalamus —> Primary gutsory cortex —> Amygdala

5 primary tastes?

Sweet, salty, sour, bitter, umami + oleogustus (Fatty)

Perception of taste?

Combo of flavours, smells, and a little bit of texture

Transduction in the body senses

Somasthetic senses (split into 3 different more senses)

3 different types of somasthetic senses

1) Skin senses

2) Kinaesthetic senses

3) Vestibular senses

Skin senses

Have neural pathways that send signals about: touch, pressure, pain, temperature

Neural pathway for skin senses

Skin —> Spinal cord —> Primary somatosensory cortex —> Limbic system (emotional processing)

Define kinaesthesia

Awareness of body movement

Propiroception

Awareness of where the body and body parts are located in relation to each other in space and in the ground

Proccessed by?

Special receptors in skin, joints, muscles, and tendons

Vestibular senses

Awareness of the balance, position, and movement of head and body through space in relation of gravity

Neural pathways?

• Semicircular canals → Vestibular nerve → Parietal cortex

Gestalt theory

Proposes the brain forms a perpetual whole that is more than the sum of its parts

• Thought to be due to innate factors

  • Brain is naturally designed to organise information into meaningful perceptions

Gestalt principles of perceptual grouping

• Figure ground relationship = To perceive objects or figures as existing background

• Reversible figure = Images in which the figure and ground can be reversed

• Ambiguous figure = Image that allows for more than one interpretation

• Similarity: Tendency to perceive things that look similar to each other as being part of the same group

• Proximity = Tendency to perceive objects that are close to each other as part of the same grouping

• Closure = Tendency to complete figures that are incomplete

• Continuity = Tendency to perceive things as simply as possible with a continuous pattern rather than with a complex broken up pattern

• Common region = Tendency is to perceive objects that are in a common area or region as being in a group

• Elemental connectedness = Tendency to perceive objects that are connected overrides both elements of similarity and proximity

• Common fate = Tendency group similar objects when they share a common motion, destination, or orientation

Law of Praganaz/Principle of simplicity

Tendency for us to perceive the simplest pattern, requiring the least cognitive effort

Bottom-up processing

Information from the external world is analyzed starting from the most basic features to construct a whole (driven by stimuli)

E.g. Gestalt principles of organization

Top down processing

 Use of pre-existing knowledge (e.g., memories, expectations, motivations) to organise individual features into a unified whole (i.e., conceptually-driven)

Examples of top down processing

• Perceptual constancy: Ability to recognise the same object despite differences in angle, position, distance, lighting etc

• Shape constancy = Tendency to interpret the shape of an object as being constant, even when its shape changes on the retina

• Size constancy = Tendency to interpret an object as always being the same actual size regardless of its distance

• Perceptual constancy = Tendency to perceive the apparently brightness of an object as the same even when the light conditions change

• Perceptual constancy = Tendency to perceive an object as the same colour even under different colours of light

Perceptual illusions

Illusions that do not match up with reality