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Perception Flashcards

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1
Q

What are the biological mechanisms that act as hard constraints on perception?

A

Place/temporal codes, tuning

These mechanisms influence how we perceive sensory information.

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2
Q

What is the general principle of perception and cognition?

A

We perceive complex and varied phenomena such as:
* vision
* hearing
* touch
* pain
* warmth
* taste
* smell

This highlights the range of sensory experiences that perception encompasses.

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3
Q

How is perception defined?

A

A constructed representation of behaviourally relevant attributes in the environment

It integrates sensory input with memory and cognition.

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4
Q

What does perception involve?

A

Representation and transformation of sensory input and integration with memory and cognition.

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5
Q

What do we sense?

A

*Light: Detected through photoreceptors sensitive to wavelength and intensity

*Chemical: Smell (airborne molecules) and taste (molecules disolved in saliva)

*Mechanical Forces: Proprioception (receptions in muscles detect limb movement) and sound (vibration in air sensed by tympanic membrane)

*Temperature: Thermoreceptors detect hot and cold

*Pain: Nociceptors detect tissue damage

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6
Q

How sensory input turning into complex representations

A

Through David Marr’s levels of analysis

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7
Q

What is the focus of the Computational Level?

A

*What problem is being solved?
E.g. How to reliably extract environmental information to guide action (such as recognising people, avoiding hazards, judging food)

Example: How to reliably extract environmental information to guide action.

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8
Q

What does the Algorithmic Level address?

A

*What representation and processes are used?
*Signals are transformed and integrated
*E.g. from eye to brain to memory

Signals are transformed and integrated from eye to brain to memory.

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9
Q

What is the Implementation Level concerned with?

A

*How is it physically implemented in the brain?
*Biological Structures- Neurons, receptors, photoreceptor types, excitation/inhibition in V1 (primary visual cortex)

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10
Q

What is psychophysics?

A

The scientific method that quantitatively relates physical stimulus properties to psychological experience.

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11
Q

Who founded psychophysics?

A

Wilhelm Wundt and Ernst Weber in 19th century Germany (University of leipzig)

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12
Q

What is the task in the light detection example?

A

*Task- Indicate whether light appears on the left or right
*Background luminance- 10 cd/m^2
*Stimulus Luminance (Ls)- Multiple levels tested

*Luminance is a measure of how much light is emitted, reflected, or transmitted from a surface in a given direction

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13
Q

What is the formula for Contrast (C)?

A

C = ΔL / Lb

E.g. Ls = 12, Lb = 10 –> C = 2/10 = 0.2
*C- Contrast
*Lb- Luminance of the background
*Ls- Luminance of the stimulus
*ΔL- Difference in luminance between Ls and Lb

Where ΔL is the difference in luminance between stimulus (Ls) and background (Lb).

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14
Q

What does Point of Subjective Equality (PSE) refer to?

A

The point where 2 stimuli appear equal to the observer observer (typically ~50% correct responses)

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15
Q

What is Just Noticeable Difference (JND)?

A

The smallest change in stimulus that can be reliably detected (~25% to 75% zone of uncertainty)

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16
Q

What does the Weber-Fechner Law state?

A

*The JND is proportional to the baseline stimulus.
*JND = k x Lb
*E.g. 100g vs 150g (50% difference) is detectable, but 1000g vs 1050g is not (5% difference)

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17
Q

What are everyday sensory thresholds for sight?

A

*Sight- See a candle from 30 miles on a clear night

*Hearing- Hear a ticking clock from 20 feet in silence

*Touch- Feel a fly’s wing drop on cheek

*Smell- Detect one from of perfume in 6 rooms

*Taste- Detect 1 teaspoon of sugar in 2 gallons of water

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18
Q

What do illusions reveal about perception?

A

They are systematic features that reveal the mechanisms at play.

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19
Q

What is the Mueller Lyer Illusion?

A

Two lines of equal length appear different due to arrowhead orientation.

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20
Q

What is Colour Constancy? What are the related constancies?

A

Objects appear the same colour despite changes in illumination.

Lightness constancy, size constancy, shape constancy

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21
Q

How is colour determined?

A

*By cone activation and contextual interpretation.

*Systems account for illumination differences to maintain object constancy

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22
Q

What must stable object representations do across viewpoints and conditions?

A

Generalise across viewpoints and conditions, so that we can separate objects from backgrounds

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23
Q

Why must vision be efficient?

A

*Due to high metabolic demands
*The brain uses ~20% of the body’s total energy
*Inefficient processing would come at high metabolic cost

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24
Q

What does visible light correspond to?

A

*A narrow band of electromagnetic radiation
*The sun emits the most photons in this band

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25
What are the evolutionary constraints?
*UV- Damaging to cells (e.g. retina, no pain receptors –> hidden damage) *Infrared- Low resolution, confused with heat, some animals like snakes use it but not humans
26
How does colour arise in materials?
From how materials reflect/absorb wavelengths (e.g. blue square reflects blue wavelengths, absorbs others)
27
Where does light hit in the eye?
The retina at the back of the eye
28
What is are Rods?
*A type of photoreceptor *They are monochromatic (light of a single wavelength or frequency) *They are sensitive to low light *Black and white vision, used at night
29
What is are Cones?
*A type of photoreceptor *There are 3 types of cone receptors (S, M, L) *S- Short wavelength (blue) *M- Mid wavelength (green) *L- Long wavelength (red)
30
What does colour vision arise from?
Comparing activation across cone types
31
What happens to images due to lens refraction?
*Images are inverted and mirrored on the retina *Left visual field = right side of the retina = right hemisphere *Top = projected to lower retina (vice versa) *Input from both eyes is combined at the cortical level
32
What are the retinal layers?
*Photoreceptors, rods and cones, at the back (deepest layer) *Transparent interneurons, bipolar and retinal ganglion cells, in front *Signals Pass- Photoreceptors –> ganglion cell –> Optic nerve –> brain
33
What is the fovea? What are it's features?
*A small central pit in the retina with dense cone concentration *It has high acuity vision (fine detail) *Light hits photoreceptors directly *Neuronal fibres avoid the fovea to reduce light scattering
34
What are the features of the peripheral retina?
*Has more rods *Larger receptive fields *Less acuity *Higher sensitivity
35
What is the blind spot?
The area where axons leave the retina with no receptors for light detection, so the brain fills in missing info
36
What does retinal convergence allow?
Detection of weak signals in the periphery
37
What do visual afterimages demonstrate?
Neurons signal relative (context dependent), not absolute, value (E.g. string as colour, afterimage is complementary colour)
38
What is monocular adaptation?
Afterimage only visible in the adapted eye
39
What are orientation aftereffects?
Staring at tilted line- Straight lines appear tilted in the opposite direction
40
Animal visions
*Humans have trichromatic vision (SML cones) *Most mammals have dichromatic vision (e.g. blue-yellow) *Some animals (e.g. shrimp) have many photoreceptor types *This highlights variety in evolutionary solutions to visual problems
41
What are receptive fields?
*Regions of the retina that influence the response of a neuron *It's small in fovea and larger in periphery (more convergence)
42
What is the centre-surround organization of retinal ganglion cells?
Excitatory centre increases firing; inhibitory surround decreases firing
43
What function do receptive fields perform?
*Contrast enhancement- Enhances edges and boarders through boundary detection *Reduce redundant signals, which saves brain resources
44
What is simultaneous brightness contrast?
*Identical grey patches appear different depending on surrounding luminance *Due to receptive fields responding differently depending on excitation/inhibition balance
45
What is primary visual cortex?
*V1 exhibits centre surround receptive fields *It processes spatial frequencies and orientations *V1 neurons act as filters for visual features *They respond to specific orientations and spatial frequencies *It processes visual features including location, shape/orientation, colour, size and distance (depth)
46
What is spatial frequency tuning?
*Spatial frequency is the number of light dark cycles per degree of visual angle *Low Frequency- Coarse detail (e.g. general shape) *High Frequency- Fine detail (e.g. texture, edges) *V1 has neurons tuned to different spatial frequencies *Human vision is most sensitive to mid-range frequencies (3-5 cycles per degree)
47
What is orientation tuning?
*V1 neurons integrate ganglion input along specific lines, sensitive to edges and orientation *Orientation specific neurons enable line and shape detection
48
What are the functions of the extrastriate cortex?
*t’s an area of the visual cortex beyond the primary visual cortex (V1) *Visual processing continues in areas V2, V3, V4, V5 (MT) *V3- Form *V4- Colour *V5- motion
49
What are the 3 stages of visual processing?
1. Low Level (basic attributes): Brightness, colour, orientation, motion 2. Mid-Level (grouping and segmentation): Grouping elements into figures vs background 3. High Level (semantic recognition): Objects and faces, an integration with memory and concepts
50
What are the functions of hearing?
Alarm/Orienting System- Detects threats or relevant stimuli without requiring sight Object Classification/Identification- Learning characteristic sounds of objects and animals Communication through Self Generated Sound- Humans, whales and others produce complex communicative signals (even dialects in whale pods) ## Footnote This function allows individuals to respond to their environment effectively.
51
How is sound defined in auditory perception?
Sound is the spherical pressure waves that travel in all directions from a source ## Footnote This definition emphasizes the nature of sound propagation.
52
what are the features of frequency?
*Number of cycles per second *1 Hz = 1 cycle per second *Frequency determines pitch ## Footnote Higher frequencies correspond to higher pitches.
53
What are the features of amplitude?
*Magnitude of the wave *Determines loudness ## Footnote The greater the amplitude, the louder the sound perceived.
54
What are simple sounds
Pure tones that consists of a single frequency ## Footnote Rare in nature, but can be synthesized.
55
What are complex sounds?
*They consist of multiple frequencies *Fundamental Frequency (F0)- Determines pitch *Harmonics- Determines timbre (texture of the sound) *Timbre allows us to distinguish between instruments ## Footnote These sounds include a fundamental frequency and harmonics.
56
Explain the Matching experiment
*Masking- When a sound (mask) makes another sound (target) harder to hear Findings: *Tones close in frequency mask more effectively *Lower frequencies are better at masking Tuning Curves: *Show bandwidth of neural channels *Can be measured through behaviour or neural recording (similar results in both) ## Footnote This is supported by findings from masking experiments.
57
What is Sound Pressure Level (SPL) measured in?
Decibels (dB) ## Footnote SPL quantifies the intensity of sound.
58
What do Equal Loudness Contours represent?
*Subjective loudness mapped across frequencies and intensities *Humans are most sensitive around 1000-6000 Hz *Loudness units- Phons (10 Phon = 1 kHz at 10dB) ## Footnote Humans are most sensitive around 1000-6000 Hz.
59
What is the Fourier Transform?
A mathematical technique that decomposes complex waveforms into simple sine waves ## Footnote It has applications in sound synthesis, recognition, and image processing.
60
What does the Primary vs secondary Auditory Cortex respond to?
Primary responds to both pure and complex tones Secondary responds to complex tones only ## Footnote This area is essential for processing auditory information.
61
What is the auditory pathway structure?
Cochlear Nerve –> Brainstem –> Inferior Colliculus –> Medial Geniculate Nucleus –> Auditory Cortex ## Footnote This structure is crucial for sound transduction.
62
What is the structure of the ear?
*Pinna/Ear Lobe: Funnels sound into the auditory canal and helps localize sound elevation *Eardrum (Tympanic Membrane): Vibrates in response to sound waves *Ossicles : Tiny Bones (Malleus, Incus, Stapes) that amplify vibration and transmit them to the oval window of the cochlea *Cochlea: Spira, fluid filled structure that contains the basilar membrane and organ of Corti *Semicircular Canals: Involved in balance
63
Transduction process in the cochlea
1) Sound vibrations cause the basilar membrane to oscillate 2)Membrane is narrow and stiff at the base (high frequencies) and wide and floppy at the apex (low frequencies) 3)Movement stimulates hair cells, bending of hair cells triggers neural firing 4)Place Code- Location of maximum membrane displacement determines pitch 5)Temporal Code- Neurons fire in sync with the sound wave’s phase (for frequencies < 1000Hz) 6) Lateral Inhibition- It sharpens pitch discrimination, inhibitory signals at the membrane edges narrow the tuning bandwidth ## Footnote It relates to how different frequencies are processed along the cochlea.
64
What is the Speech Range for optimized communication?
Approximately 300-3400 Hz ## Footnote This range is crucial for effective verbal communication.
65
What is Tinnitus? How is it treated?
*Constant ringing due to damaged/disinhibited hair cells *Treated by masking with lower frequency boosts ## Footnote Treatment often involves masking with lower frequency boosts.
66
What is the Cocktail Party Effect (study?
1) Study conducted by Cherry (1953) 2)Easier to follow 1 of 2 messages if they are sent to separate ears 3)Selective Attention: Can be directed to one ear and can shift in response to meaningful stimuli (e.g. hearing your name) *Top-Down Effects- Language, familiarity and visual cues help with auditory separation ## Footnote This phenomenon illustrates selective attention in auditory processing.
67
What is the function of auditory scene analysis?
*Track moving sources (e.g. helicopters) *Separate multiple overlapping sounds (like tapping and birds)
68
What is sound localisation?
Sound localisation is processed early in the brainstem to determine source location
69
What aids in sound localization in the elevation dimension?
Pinnae and spectral filtering ## Footnote These features enhance the ability to determine sound source height.
70
Features of Azimuth (Horizontal)?
*Interaural Time Difference (ITD)- Time lag between ears *Interaural Level Difference (ILD)- Sound is quieter in the far ear due to the acoustic shadow of the head

Cognitive Psychology (3 decks)

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