Unit 5: Sensation & Perception (Chapter 4)

Question 1

Colour

Answer 1

A psychological constructon of the brain. Not a property of an object.

Ex: Lemons “are” yellow.
Ex 2: Blue and black / white and gold dress.

Question 2

Colour constancy

Answer 2

The brain’s ability to recognize colour of an object as being the same even under different lighting conditions. It adjusts its perception of color to hold it constant, accounting for changes in lighting conditions & other contextual factors (e.g., shadows)

Ex: Potted plant and tiles shadow illusion.

Question 3

Sensation

Answer 3

Raw data; process by which sensory organs detect environmental stimuli & convert them (though transduction) into electrical signals for the nervous system.

Question 4

Stimulus

Answer 4

Something that elicits a reaction from our sensory systems.

Ex:
- Light (vision)
- Sound waves (hearing)
- Mechanical pressure, vibration, temperature, pain (touch)
- Chemicals in food or drink (taste)
- Airborne chemicals (smell)

Question 5

Transduction

Answer 5

Transformation of sensory stimulus energy into neural impulses. “Common language” used by all sensory systems (i.e. no category for just the eyes, or just the mouth, etc.).

Ex: Light entering your eyes is converted into neural impulses by specialized cells.

Question 6

Perception

Answer 6

Creating a coherent narrative using data; brain’s interpretation of these electrical signals to create an internal representation of the world. Relies on both raw sensory data (bottom-up processing) and prior experience, knowledge, and expectations (top-down processing).

Ex: Brain processes incoming neural signals, allowing you to recognize the expression on your friend’s face

Question 7

Psychophysics

Answer 7

Study of the relationship between the physical qualities of environmental stimuli (physics) and our mental experience of them (psyche).

Earliest of said studies tried to establish the limits of awareness.

Question 8

Absolute threshold

Answer 8

Minimum amount of stimulus that can be detected at least 50% of the time (NOT THE LOWEST). Inversly related to sensitivity (lower absolute threshold = higher sensitivity, vice-versa).

Thresholds are not static! Sensory systems respond more to changes than steady states.

Question 9

Signal detection theory

Answer 9

An approach to measuring thresholds that takes into account both the intensity of the stimulus and psychological biases for a more accurate assessment. Takes place under conditions of uncertainty.

Ex: When different radiologists check for tumours, one might detect more than the other.

Question 10

Signal detection theory terms (in relation to radiologist example)

Answer 10

Tumor present: Responds yes (Hit); got it right
Tumor present: Responds no (Miss); didn’t see it
No tumour: Responds yes (Flase Alarm); incorrect diagnosis
No tumour: Responds no (Correct Rejection); confirmed there was none

Question 11

Liberal bias

Answer 11

Low threshold for detecting signal (i.e. higher rate of hits, but also higher rate of false alarms).

Signal detection depends both on strength of signal and individual bias. To properly calculate sensitivity, one must include both signal present and absent trials, so compare hits to false alarms.

Question 12

Conservative bias

Answer 12

High threshold for detecting a signal (i.e. lower rate of false alarms, but also lower rate of hits).

Signal detection depends both on strength of signal and individual bias. To properly calculate sensitivity, one must include both signal present and absent trials, so compare hits to false alarms.

Question 13

Alive or not? study

Answer 13

A person’s answer will likely depend on how socially connected or lonely they feel. Lonelier people will require fewer human characteristics to detect an animate object due to social cravings (liberal bias). Takeaway: Unmet belongingness needs can shape social perception.

Question 14

Just-noticeable difference/difference threshold

Answer 14

Smallest difference between two stimuli that can be detected at least 50% of the time (i.e. reliably). Will depend on the size of the stimuli being compared.

Question 15

Weber’s law / Weber’s fraction

Answer 15

As stimuli get larger, differences must also become larger in order to be detectable (i.e. the likelyhood of percieving a stimulus change is proportional to the magnitude of the stimuli). Weber’s fraction = ΔI/I, where Δ = minimum change, I = magnitude of stimulus

Ex: Drinking a glass of clean water with sugar added into it vs pop with sugar added into it.

Question 16

Weber’s Law Practice Problem:
While you are on vacation with your brother, he tells you about a psychological study he recently participated in. When he was holding a 50-gram weight, he couldn’t tell that extra weight had been added until the added weight was more than 5 grams. According to Weber’s Law, how much of your stuff can you add to his 25-kg suitcase without his noticing?

Answer 16

Weber’s fraction = ΔI/I, where Δ = minimum change, I = magnitude of stimulus.
Weber’s fraction = 5/50 = .1
25,000 g x .1 = 2,500 g = 2.5 kg

Question 17

Adaptation

Answer 17

Stop noticing a stimulus that remains constant over time. This is useful, since it allow us to focus on changes in our environment.
- Sensory adaption occurs at the level of the sensory receptors
- Perceptual adaptation occurs in the perceptual centers of the brain.

We don’t stop seeinf things due to the tiny involuntary movements our eyes constantly make (microsaccades).

Question 18

Vision

Answer 18

Processing of light reflected from objects.

Question 19

Visible light

Answer 19

Type of electromagnetic radiation emitted by sun, artificial light sources, etc. that can be detected by the eye. Made of of particles that move in waves (photons).

Question 20

Wavelength (Vision)

Answer 20

Distance betweem successive peaks. Decoded as colour. Inversly related to frequency.

Question 21

Frequency (Vision)

Answer 21

Number of cycles per second. Inversly related to wavelength.

Question 22

Amplitude (Vision)

Answer 22

Height of the wave. Decoded as brightness.

Question 23

Cornea

Answer 23

Transparent tissue covering front of eye, focuses light.

Fun fact: 50% of the cerebral cortex is devoted to vision. 11% is devoted to touch, etc.

Question 24

Iris

Answer 24

Opaque, colourful muscle encircling the pupil. Can increase or decrease size of pupil, determining how much light enters (by contracting, expanding).

Question 25

Pupil

Answer 25

Hole in the iris where light enters the eye.

Question 26

Lens

Answer 26

Membrane at front of the eye that focuses incoming light on the retina. The image on the retina is upside down, but our brains can interpret this. ## Footnote Remeber as a camera lens that focuses in on something, able to adjust brightness on iPhone.

Question 27

Accomodation

Answer 27

Adjustments of the lens’s thickness by specialized muscles in order to change the degree to which it bends light. Lens becomes elastic with age, less accommodation.

Question 28

Retina

Answer 28

Surface in the back of the eye containing receptor cells specialized for transducing light (photoreceptors).

Question 29

Rod

Answer 29

Photoreceptor cell that primarily supports nighttime vision. ## Footnote Remember as "fishing in the dark".

Question 30

Cone

Answer 30

Photoreceptor cell that is responsible for high-resolution color vision. ## Footnote Remember as COne, COlour.

Question 31

Visual transduction

Answer 31

When light reaches the photoreceptors, light- sensitive molecules (photopigments) undergo chemical reactions generate electrical signals. Said signals are transmitted along the optic nerve.

Question 32

Blind spot

Answer 32

Area in the middle of the visual field where there are no photoreceptors and no information can be received. Brain fills in blindspot.

Question 33

Differences between rods and cones

Answer 33

**1)** Rods all have the same type of photopigment, but cones contain one of three varieties of photopigments. The mulltiple photopigments of the cones allows us to see colour. **2)** Rods contain an extremely light-sensitive pigment called rhodopsin—allows us to see in the dark. **3)** Differ in their quantity and distribution across the retina: - Ratio of rods to cones is 20:1 - Cones concentrated in fovea (small pit in centre of retina). NO RODS IN FOVEA. - Most rods are in central periphery (why peripheral vision is better in dim light/darkness). **4)** Cones have more direct connections to neural cells; rods converge more. **5)** Cones receive more cortical representation (allows more detail to go to the brain). **6)** Cones have higher acuity (sharpness and specificity), whereas rods have higher sensitivity (ability to simply detect stimuli, ex: a flame, from far away!).

Question 34

Rhodopsin

Answer 34

The rod photochemical that breaks down and becomes inactive when exposed to bright light (so as not to overstimulate us) and regenerates in the dark (takes about 25 mins, evolutionary perspective of sunset to darkness). ## Footnote Ex: Turning a light on and off, and your eyes get used to the darkness/the light.

Question 35

Colour vision

Answer 35

Objects differ in their capacity for absorbing or reflecting light, and thereby reflect different wavelengths to our eyes. Each cone has 1 of 3 distinct varieties of photopigment, which are sensitive to short (blue), medium (green) or long (red) wavelengths. At night, rods are most sensitive to blue-green wavelengths.

Question 36

Trichromatic theory

Answer 36

The three types of cone cells work together to produce perception of colour.

Question 37

Colour blindness

Answer 37

Some people only have two, not three, types of cone photochemicals (dichromocy) - most typically red or green. Linked to y-chromosome. If you miss 2 of the 3 types of cone photochemicals, you can't see any colour.

Question 38

Optic nerve

Answer 38

A bundle of axons that converge from the retina and transmit action potentials to the brain.

Question 39

Opponent-process theory

Answer 39

Our perceptual systems treat the visible spectrum as a circle, where the two ends meet (i.e. purple is an illusion). Plus, the informaton from the cones is seperated into 3 sets of opposing or oppenent channels in the ganglion layer. Thus, you cannot see "reddish-green" or "yellowish-blue" since they will cancel each other out. Afterimages occur when cones "tire out" (adapt) from looking at a certain colour, which decreases the cones ability to inhibit opposing colours in the ganglion cell (which is why you see the opposite colour when looking away). ## Footnote Ex: Stare at green and black Canada flag.

Question 40

Ganglion cells

Answer 40

Located in the retina. Receive input from cones (via bipolar cells). Organized in pairs that respond to opposing colours: red-green, blue-yellow, white-black. ## Footnote Ex: Some ganglion cells are excited by red, inhibited green (R+/G-), and vice versa. Thus, when seeing an apple: R+/G- cells excited, R-/G+ inhibited, which tells the brain “there’s more red here than green”

Question 41

Object identification (hierarchical due to increasing complexity)

Answer 41

**1)** Visual information travels along optic nerve to optic chiasm, where axons from each side of the retinas are diverted to corresponding side of the brain. **2)** Thalamus (relay station) passes information on to primary visual cortex. **3)** Image (from retina) reconstructed in primary visual cortex (also organized as a map) thanks to feature detectors. **4)** Visual association cortex combines incoming sensory inputs with prior knowledge & expectations. **5)** Additional processing in temporal lobe allows you to recognize specific objects, like faces.

Question 42

Feature detectors

Answer 42

Specialized neurons that respond to specific attributes of visual stimulus (ex: edges, angles, orientation).

Question 43

Prosopagnosia

Answer 43

Inability to recognise faces. Those who suffer from this may only recognize incoherent shapes. **Result of damage to the visual association cortex.** ## Footnote Ex: "The Man Who Mistook His Wife for a Hat".

Question 44

Ventral stream

Answer 44

Processes “what” information (from occipital to temporal lobe). - Responsible for recognizing objects and faces. - **Damage here leads to visual agnosias where subject is not able to recognize object.** ## Footnote Dissociable from the "where" pathway.

Question 45

Dorsal stream

Answer 45

Processes “where” information. - Responsible for determining location and the perception of movement. - **Damage here may result in seeing movement as series of statistic “snapshots”.** - Stop-motion movies use apparent motion, aka the phi phenomenon (illusion where snapshot images appear to be fluid) to create stop-motion movies. ## Footnote Dissociable from the "what" pathway.

Question 46

Gestalt psychology

Answer 46

perspective that we perceive whole, organized patterns & objects through an unconcious mental process. - Gestalt = German for “organized shape” or “whole form”. - “The whole is different from the sum of its parts”. Ex: Illusiory contours (triangle image).

Question 47

Gestalt principles

Answer 47

1) Proximity: We percieve features as grouped when they are close together. 2) Similarity: We group together things that look alike. 3) Closure: We fill in gaps to create continuous edges, allowing us to percieve an object as a whole. 4) Good continuation/Continuity: We tend to look for smooth, contininuous patterns in objects. 5) Synchrony: We group itemps together that move at the same time. 6) Connectedness: We group tegether objects that are connected.

Question 48

Figure

Answer 48

Object of main focus. ## Footnote Often not arbitrary, but guided by certain principles. Ex: Reversible figures (rabbit/duck, old lady/young woman).

Question 49

Ground

Answer 49

Background. ## Footnote Often not arbitrary, but guided by certain principles. Ex: Reversible ground figures (vase/2 faces).

Question 50

Bottom-up processing

Answer 50

Raw and sensory data; body to brain.

Question 51

Top-down processing

Answer 51

Prior knowledge, experience, and expectations; brain to body. A perceptual set, related to top down processing, is a predisposition that influences what we percieve based on recent experience or context.

Question 52

Depth perception

Answer 52

Image projected on retina is 2-D. Brain uses various cues to translate this 2-D image into 3-D perception of real-world object. Uses both binocular and monocular cues.

Question 53

Binocular cues

Answer 53

Depth information gathered from the separation between an individual’s two eyes; compares both views to construct 3-D views.

Question 54

Binocular disparity

Answer 54

Cue for depth perception stemming from the slightly different (disparate) views that two eyes have of an object or scene (i.e. the magnitude of difference between the images projected on an individual's two eyes). - More disparate views for objects close by, more similar as object moves further away. - This is used by the brain to gauge depth. ## Footnote Ex: Staring at finger close to your face v.s. far away.

Question 55

Monocular cues

Answer 55

Depth information that can be gathered using just one eye.

Question 56

Motion parallax | Example of monocular cue

Answer 56

When you move your head, objects closer to you appear to move faster than objects farther away. ## Footnote Ex: Closer objects whipping by and going in opposite directions.

Question 57

Monocular cue examples (pt.2)

Answer 57

- Linear perspective: Parallel lines appear to converge in distance. - Interposition: Nearby objects occlude more distant ones. - Relative height: Objects further away appear closer to the horizon. - Relative size: Objects further away appear smaller than nearby objects.

Question 58

Size constancy

Answer 58

Objects further away project a smaller image on the retina (we can still see the object as a certain size, though). The brain accounts for variation in retinal images in terms of distance, and interprets it as a cue for depth. *Can leverage knowledge of various depth cues to create optical illusions (ex: monster chaasing the other, moon seems bigger).*

Question 59

Sound

Answer 59

Waves of vibration in the form of mini collisions between adjacent molecules in a medium like air or liquids.

Question 60

Amplitude (Sound)

Answer 60

Height of the wave, measured in decibels (dB). **Determines percieved volume of the sound. Higher amplitude = louder, low amplitude = softer.**

Question 61

Frequency (Sound)

Answer 61

Number of cycles that occur per second, measured in Hertz (Hz). Inversly related to wavelength. **Determines pitch (highness or lowness of the sound).**

Question 62

The human auditory stimulus

Answer 62

- On average, can hear range of frequencies from 20 to 20,000 Hz. - Some individual variation & changes with age. - Best attuned to frequencies corresponding to human voice. - Other animals can hear sounds at infrasonic (e.g., elephants) and ultrasonic (e.g., bats) ranges of spectrum. - Humans cannot hear infrasounds, but some evidence that infrasound increase physiological arousal (activation of the sympathetic nervous system) & symptoms like nausea and sleep disturbances.

Question 63

Human ear

Answer 63

Divided into outer, middle and inner ear. Its components work together to amplify, colect an transducer vibrations into neural signals.

Question 64

Pinna

Answer 64

Captures & funnels soundwaves through auditory canal towards the middle ear.

Question 65

Middle ear

Answer 65

Contains the eardrum and the ossciles (the hammer, the anvil, and the stirrup).

Question 66

Ossciles

Answer 66

Tiny bones located between two membranes (tympanic membrane / eardrum & oval window). Made up of the hammer, the anvil, and the stirrup. – Amplify vibrations of incoming soundwaves. – Help protect the inner ear from very loud noises.

Question 67

Inner ear

Answer 67

Contains the vestibular system and the cochlea.

Question 68

Cochlea

Answer 68

A spiral structure in the inner ear where the basilar membrane, containing auditory sensory neurons, is located.

Question 69

Basilar membrane of the cochlea

Answer 69

Contains specialized receptor cells for transducing vibrations transmitted into the inner ear into neural signals. - Occurs when hairlike structures named auditory cilia bend in response to vibration. - Resulting signal is carried along the auditory nerve to the brain.

Question 70

Place theory

Answer 70

Theory of pitch perception proposing that different sound frequencies are processed at different parts of the basilar membrane. The further into the basilar membrane (into the “swirl”), the lower the frequency. - Accounts for selective hearing loss: cilia loss can occur at specific locations along basilar membrane. - Best explains perception of higher pitched sounds, but doesn't explain perception of lower pitch sounds (which have longer wavelengths, and thus lower frequencies).

Question 71

Frequency theory

Answer 71

Theory of pitch perception proposing that frequency of auditory neuron firing matches frequency of sound wave. - For higher frequencies, groups of neurons alternate firing to match the frequency. - Best explains perception of low-pitched sounds (celia can fire up to 1000 per second, but we can perceive up to 6000 Hz), does not account for difference in pitch and loudness perception.

Question 72

Pitch perception

Answer 72

Combination of frequency of neural firing (frequency theory) and location of stimulation on basilar membrane (place theory).

Question 73

Primary auditory cortex

Answer 73

Located in temporal lobe. Contains place-frequency maps. Frequencies represented tonotopically (similar frequencies represented next to each other). Plasticity may occur if an organism is trained to percieve a particular frequency as a cue, thus increasing the cortical neurons that respond to said frequency.

Question 74

Sound localization

Answer 74

Brain compares information coming from each ear, along with visual cues, to determine relative timing & intensity. Makes it difficult to locate sound if it's coming from above (like at the movies). E.g., if sound is coming from left side: - Relative timing: sound will enter left ear slightly before right ear. - Intensity: Head creates “sound shadow”, reducing intensity of sound in right ear.

Question 75

Tactile sense

Answer 75

Perception of touch.

Question 76

Mechanoreceptors

Answer 76

Sensory receptors that respond to mechanical stimulation (pressure, touch, vibration, stretch). Different types that respond to different types of stimulation. - Myelinated receptors that allow fine-grained discrimination (movement, texture, localization). - Unmyelinated receptors that respond to low-pressure, low velocity tacticle stimulation. Such stimulation found in intimate, affiliative interactions.

Question 77

Receptors in the skin

Answer 77

Allow us to detect temperature and different types of noxious stimulation that causes pain. Skin sensations are often result of activation of multiple receptor types. Ex: Cold + pressure = wetness. As with other senses, respond most strongly to changes in stimulation. Ex: Running cold hands under lukewarm water will produce sensation of heat

Question 78

Somatosensory homunculus

Answer 78

Visual representation of how areas of the body are represented based on their sensitivity rather their size. Most "important" areas of the body get the most real estate.

Question 79

Primary somatosensory cortex

Answer 79

The region of the brain where the processing of touch sensations occurs.

Question 80

Association areas (secondary somatosensory cortex)

Answer 80

Enable recognition of objects & more complex sensations (e.g., sensation of motion on the skin). **Damage to these areas can result in tactile agnosia = inability to recognize object by touch.**

Question 81

Interoception

Answer 81

Ability to perceive signals originating within the body (Ex: breathing, hunger, thirst). Crucial for being able to maintain steady internal state.

Question 82

Insula

Answer 82

Plays key role in processing these signals, imbues them with emotional & motivational significance. - Ex: May interpret signals of sympathetic nervous system activation as anxiety (misreading = generalized anxiety). - The ”social touch” receptors project directly here; may explain why social touch is experienced as soothing. Ex: Baboons grooming one another, "everything is ok" touch. - Also thought to play a role in the experience of the “self” (distinguish yourself from others).

Question 83

Proprioception

Answer 83

Sensory experience of the body’s position in space. Relies on specialized receptors (proprioceptors) in muscles, tendons, & joints, which detect changes in muscle length, tension, & joint position through mechanical deformation.

Question 84

Vestibular system

Answer 84

System in the inner ear that helps maintain balance by detecting head movements and motion. - Detects position of head relative to ground, linear acceleration, rotational movements of the head - Movement of fluid in semicircular canals of the inner ear triggers cilia cells. Information travels along auditory nerve to medulla & cerebellum, and, eventually, (via the thalamus) to somatosensory cortex and primary motor cortex.

Question 85

Vestibular working with the visual system

Answer 85

Work together to maintain balance. Harder to maintain balance withour input from visual system (ex: spotting while turning).

Question 86

Kinesthesis

Answer 86

The senses responsible for monitoring the position and the movement of the body, including proprioception and the vestibular system.

Question 87

Vestibular-ocular reflex

Answer 87

Reflex that helps stabilize your gaze during head movements. Wihtout it, you would have "blurry" vision all the time. - Signal travels from semicircular canals to the brainstem, which then coordinates eye muscles to move eyes in opposite direction of head movement. - **Mismatch between senses can lead to motion sickness. Theory = brain detects this as poison + triggers response.** ## Footnote Ex: Have your friend spin with their eyes closed, and open their eyes. See if they move in the direction opposite the way they were spinning.

Question 88

Olfaction

Answer 88

Sense of smell. Important functions: - Detection of hazards (e.g., smoke, spoiled food). - Enhances taste. - Important for emotional & social experiences. - Loss of smell and depression correlated (although causality not clear).

Question 89

Epithelium

Answer 89

Mucous membrane in the nasal cavity that contains olfactory receptor neurons with their own cilia (olfactory cilia). - Chemical odor molecules bind to cilia like in a lock-and-key system, which triggers action potentials through the bundle of receptor neuron axons which comprise the olfactory nerve.

Question 90

Olfactory bulb

Answer 90

Structure just above the nasal cavity that receives input from olfactory sensory neurons. Involved in basic processing: i.e. can distinguish good and bad smells.

Question 91

Glomeruli

Answer 91

Sperical clusters of neurons located in the olfactory bulb. Different parrerns of activation across glomeruli encode different odors.

Question 92

Higher level olfactory processing (transduction pt.2)

Answer 92

- Information from olfactory bulb is sent directly to parts of the limbic system (amygdala and hippocampus), which accounts for strong odour-memory connections and the emotional motivational force of odours. - Additional links to primary olfactory cortex in the temporal lobe and olfaction association cortex located in underside of frontal lobes. Allows us to identify and discriminate odours, integrate contextual information.

Question 93

Smell as a component of flavour

Answer 93

An opening (nasal pharynx) connects back of mouth cavity with nasal cavity. Allows us to smell substances that have entered the mouth. Thus, food flavour consists of both the stimulation of the taste receptors in the mouth and smell receptors in the nose. Both inputs converge in orbitofrontal cortex (part of the olfaction association cortex).

Question 94

Olfactory sensitivity differences

Answer 94

- Individual differences: genetic component, but also influenced by experience. - Deterioration of smell sensitivity with age; may contribute to decrease in ability to taste food, as well as depressive symptoms. - Women generally more sensitive to odours (evident during reproductive years, more pronounced during pregnancy). Important for mate selection, avoiding to poison the fetus.

Question 95

Genetic component to interpersonal "chemistry"

Answer 95

Major Histocompatibility Complex (MHC) genes play significant role in immune system; help recognize and respond to pathogens. Selection of MHC-dissimilar mates may confer benefits for offspring (genetic variation). ## Footnote Ex: Study asked women to rate odours of t-shirts previously worn by group of men. Odours of men with dissimilar MHC antigens more attractive. Replications not consistent though.

Question 96

Gustation

Answer 96

Sense of taste. Chemical molecules in food stimulate taste receptors contained inside taste buds on the tongue - Receptors correspond to 1 of 5 taste molecules (sweet, salty, sour, bitter, savoury/umami). - NOT organized into different regions on the tongue.

Question 97

Primary gustatory cortex

Answer 97

Located in the insula. Sends connections to various cortical areas, including orbitofrontal cortex, where neural signals for taste and smell are combined (transduction). - **Damage in this area results in loss of conscious experience of taste.** - Artificial stimulation produces experiences of taste.

Question 98

Importance of taste

Answer 98

Thought to have evolutionary functions: - Promote increased nutrition. - Prevent intake of poison or disease-causing substances. However, human may learn to enjoy bitter foods that are safe for consumption. ## Footnote Ex: Women have more sensitivity to bitter tastes, heightened sensitivity during pregnancy (avoid poisonning fetus). Ex. 2: Heightened bitterness sensitivity in children (learn what to eat and not to eat).

Question 99

Sensory interactions / integration

Answer 99

Various sensory systems are integrated to create a unified perceptual experience. ## Footnote Ex: - Visual signals and vestibular signals are integrated to inform balance. - Olfactory signals interact with gustatory signals to perceive flavor. - Visual signals inform auditory signals and affect what we perceive as speech sounds.

Question 100

Visual dominance

Answer 100

When sight and sound are in conflict, sight usually wins. - Ventroliquist effect = Sound localization is driven by visual stimulus. - McGurk effect = Visual stimulus changes perception of sound (Ex: ba vs fa). ## Footnote Ex: Rubber hand illusion = stroking fake hand while stroking real hand, brain "adopts" fake hand.

Question 101

Additional examples of top-down processing:

Answer 101

- Hedonic quality of touch is moderated by contextual variables: Touch is more pleasant when paired with smiling (vs. frowning) face. - Pleasantness of touch decreased when paired with disgusting odour. - Taste is influenced by contextual variables: The kinds of foods we grow up eating can shape likes and dislikes. Wine tastes better if we think it’s more expensive. Something palatable might taste aversive if we were expecting a different flavour.

Question 102

Takeaway of perception

Answer 102

**Our perceptions are not a direct read out of objective properties of objects out there in the world, but are brain’s construction of “what makes sense”.** - Not aware that this is happening—our perceptions feel ”real”. - Highly adaptive, but can sometimes lead to illusions or misperceptions.

Question 103

Visual association cortex

Answer 103

Combines incoming sensory inputs with prior knowledge & expectations. **Damage = Inability to recognise faces. Those who suffer from this may only recognize incoherent shapes.**

Question 104

Reversible figures

Answer 104

Demonstrate how our overall perception of an object may differ from the elements from which its perception is derived.

Question 105

Illusory contours

Answer 105

One example of how the whole can affect perception of parts. Visual stimuli with illusory contours activate edge-detector neurons in the primary visual cortex. Due to the fact that higher areas that receive input from primary visual area also feed back into these primary areas & affect neural activation there.