PSYU2247 Lecture Notes PDF

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PSYU2247 Notes W1 – Introduction & General Principles/Methods ............................................................................... W2 – Sound, Ear & Brain/ Auditory Perception ................................................................................... W3 – Auditory Percept...

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PSYU2247 Notes W1 – Introduction & General Principles/Methods...............................................................................2 W2 – Sound, Ear & Brain/ Auditory Perception...................................................................................9 W3 – Auditory Perception/ Body Senses............................................................................................21 W4 – Body/Chemical Senses..............................................................................................................41 W5 – Light, Eye & Brain.......................................................................................................................51 W6 - Spatial Vision..............................................................................................................................57 W7 – Colour Vision..............................................................................................................................69 W8 – Motion Perception.....................................................................................................................81 W9 – Depth Perception.......................................................................................................................94 W10 – Visual Development..............................................................................................................106 W11 – Face Perception & Face Memory...........................................................................................115 W12 – Object Perception + Multisensory Integration......................................................................123 W13 - Revision..................................................................................................................................148

W1 – Introduction & General Principles/Methods Introduction 

Practicals o 4 per semester  Either weeks: 3, 5, 9 & 11  OR 4, 6, 10 & 12

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Assessments o Online Quizzes (16%)  Weeks 3-12  Open 10am Tuesday - Close 9:59am The Next Tuesday o Practical Worksheets (9%)  Best 3 of 4 worksheets o One-hour Mid-semester test (25%)  Tuesday 6th April 10am  45 Minutes within a 1.15-hour window  25 Multiple Choice Questions (Open book) o 90-minute Final Exam (50%)  50 Multiple Choice Questions  2-hour window to open/ Possibly in person or online

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General Principles/Methods •

Physical stimuli are “transduced” into nerve pulses by our sense organs o We experience these as a reconstruction or representation of the world (Sounds, shapes etc

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Three observations made at the complexity of brain processes involved in perception o Large proportion of the cerebral cortex is devoted to perception o Despite the complexity of computers, there is still no device which can match the perceptual proficiency of even an infant o As a result of brain damage, some people suffer deficits in perceptual capabilities

Sensation, Perception and Sensory Modality 

Sensations are conscious experiences generated by stimulation of a sense organ such as the eye: e.g., awareness of a bright camera flash o Sensations are immediate and automatic o Simple Sensations = qualia (private, accessible to the only person who has them)

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Perceptions are complex, meaningful experiences of objects and events o Perception can take time to reach a stable state, and may require effort

Perception: Our link to reality • • • •

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Perception deals with the relationship between physical stimuli & their subjective, or psychological correlates There is no other way for information to enter the brain Perception determines what we believe is real and mediates everything we have ever learned Senses: o Sight (Visual) o Hearing (Auditory) o Smell (Olfactory) o Taste (Gustatory) o Touch (Tactile)  Balance (Equilibrioception)  Body Awareness (Proprioception)  Heat Better Classification o Vision o Audition o Chemical Senses  Gustation  Olfaction o Body Senses  Somatosensorial  Taction/Haptics  Proprioception  Equilibrioception

Which areas of Psychology are impacted by Perception? 

Neuropsychology o Apperceptive/Associative Agnosia  Inability to recognise objects  Due to a perceptual problem  See also agnosia in other senses (auditory. Tactile, etc.) o Phantom limbs/pain (Feeling in limbs that are not there anymore) o Rubber Hand illusion o Alien hand syndrome

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Clinical Psychology o Eating Disorders  Body Image distortion  A perceptual component o Inability to recognise facial emotion in…

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Psychopaths (fear, sadness) People with depression People with autism People with schizophrenia

Forensic Psychology o Eyewitness testimony  Weapons focus  Facial identification  Police identity parades  Other Race effect

Illusions of Spatial Vision     

Simultaneous brightness contrast Craik-O’Brien/Corn sweet Illusion Adelson Checkerboard Café Wall Illusion The Fraser Spiral

Principles & Methods 

Physiological Principles o Transduction  First stage of any sensory process  Receptors turn energy into neural signals  Impulses travel along axons, to terminals which release neurotransmitters across synapses to be received by another cell

o

Hierarchical Processing  Neural impulses travel “up” the system to the cortex  “Relay station” in the thalamus (except for olfaction)  Higher cortical areas also involve lateral & feedback connections  Bottom-Up vs. Top-Down o Bottom-Up  Flow of information from sensory receptors towards “higher” cortical areas with increasing levels of complexity o Top-Down  Prior knowledge influences what is perceived  Bottom-up AND Top-down o It is not a dichotomy o Both exist

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o

Selectivity  Within each sense, stimuli can vary along various dimensions (e.g., lines vary in location, length, orientation, etc.)  Cells are selective for stimuli with certain characteristics  Response will be smaller the more the stimulus differs from the preferred stimulus  Tuning – cell is tuned to 0 degrees (vertical)

o

Organisation  Within sensory brain regions there is often an orderly progression of stimulus preferences  Most “important” range of stimulus values is processed by a larger amount of cortex – “cortical magnification”

o

Specific Nerve Energies  Each sense projects to a different cortical area  The nature of a sensation depends on which neurons are stimulated, not on how neurons are stimulated

o

Plasticity  Neural mechanisms are modifiable  Development  Recovery from brain injury

o

Noise   

Neural firing is stochastic Precise firing rate determined mostly by stimulus but also by other random factors Spontaneous Activity – cells fire a little even with no stimulus

Perceptual Principles 

There must be bottom-up, otherwise how would information get in Patients in a coma, or anaesthetised animals show substantial activation through the visual pathway Top-down influences are clear in the dolphin example and many others

Detectability o Measuring Detection

o o

o

More intense the stimulus, the more likely you are to be able to detect it Detection threshold  The intensity required for detecting a stimulus  E.g., How light does a circle have to be to detect against a black background  Lower threshold is better Sensitivity  The opposite of threshold  Higher sensitivity is better

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Sensory Magnitude o Measuring perceived intensity o More intense stimulus  higher magnitude of sensation o Measure with Magnitude Estimation technique  Present a “modulus” stimulus & call it “10”  Participants rate various stimuli differing in intensity o Compressive non-linear functions (except for electric shock)  If you double the intensity of electricity, sensation would more than double

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Discrimination o Telling things apart o Discrimination threshold  The difference between two stimuli required for successful discrimination  Sometimes called the “just noticeable difference”  E.g., how different in brightness do 2 circles have to be before we can tell them apart  Lower is better

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Adaptation o Consequences for detection o Consequences for perceived intensity & discrimination o Prolonged stimulation results in a decrease in the rate of firing (physiology) o Various perceptual consequences  Increased detection thresholds for same/similar stimuli  Reduction of perceived intensity for similar suprathreshold stimuli  Perceived properties of others similar stimuli can appear biased  E.g., the motion aftereffect that we saw

Anatomical Methods (Dead Brains)  

Visible Differences o White/Grey Matter Staining o Reveals axons/connections o Reveals cell body density & size o Reveals activity (Cytochrome oxidase)

Recording Techniques (Live Brains) 

Invasive (mostly Animals) o Single cell recording  Anaesthetised or awake  Microstimulation (awake)  High Spatial & temporal resolution  Difficult to get the big picture o Optical Imaging  Blood Flow dependent changes  Small area of cortical surface  Slow response o Non-invasive (mostly humans)  Visually Evoked Potential (VEP) & Magnetoencephalography (MEG)  Measures electrical currents or magnetic fields from cortex with sensors on the scalp o But which cells are responsible o Fast Responses

Lesions   

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Animal Studies o Neurotoxins or surgery Human Neuropsychology o Usually diffuse damage, and often varying patterns of deficit Problems o Damage to fibres passing through can affect areas far from lesion o Brain recovers from damage (Plasticity) o Need to know the right test Transcranial Magnetic Stimulation (TMS) o Temporary o Magnetic field “knocks out” cells over a broad area o Temporally precise, spatially imprecise

-------------------------------------------------------------------------------------------------------------------------------------Readings – Chapter 0 & 12 What is vision? 

Vision is for humans to make sense of what is out there and to interact with it, and to actively seek information about the world

Illusions 

Adaptation: Temporarily alter our visual systems o E.g., Getting off freeway and now 50km/h feels slow

Different Senses Physical Messenger – what carries the information? Distance Spatial Detail – How well can we resolve fine detail in the scene? Time Detail – How well can we resolve whether things are changing fast in scene? Does the sense start and stop rapidly?

Vision Light

Hearing Sound

Touch Surface Shape

Smell Chemicals

Taste Chemicals

Close + Far High Detail

Close + Far

Close

Close + Far

Close

Poor Detail

High Detail

Poor Detail

Poor Detail

High Detail

High Detail

Medium Detail

Poor Detail

Poor Detail

Yes

Yes

Yes

No – smell lingers

No – have aftertaste

W2 – Sound, Ear & Brain/ Auditory Perception What is sound? 

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Sound consists of pressure waves carried by vibrating air molecules o E.g., Tuning fork:  Making a fork vibrate, gives off a ‘pure tone’ Sound Waves o A graph of pressure changes over time is a ‘waveform’ o Number of cycles of compression and refraction is known as frequency  Higher the frequency of a soundwave, the higher the pitch we hear  Lower the frequency, the lower the pitch

Properties of Waves  

The waveform for a pure tone can be described as a “sine wave” Critical features (or “parameters”) of a sine wave

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1. Frequency a. How many full waves in a second? Measured in Hertz (Hz) and corresponds to the pitch of the sound 1 full cycle per second is 1Hz

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The waveform for a pure tone can be described as a “sine wave” Critical features (or “parameters”) of a sine wave 2. Amplitude a. How high is the wave? Measured in decibels (dB) and corresponds to loudness of the sound

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The waveform for a pure tone can be described as a “sine wave” Critical features (or “parameters”) of a sine wave 3. Phase a. Defines a particular point on a waveform. Measured in degrees and corresponds to changes to the perceived quality of the sound

Complex Sounds: Adding Waves Together 

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Sound waves are “Linear”, i.e.. they add together logically (sum

the values at each point in time). Natural sounds are a collection of simple sine waves added together. The waveform of any sound can be expressed as a sum of sine waves with different freqs., amps., and phases. Just as you can add sine waves to make more complex waveforms, you can do the opposite too. Decomposing a complex sound into its component frequencies is called “Fourier analysis”.

Plotting Complex Sounds  

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We can re-plot the sound as amplitude vs. frequency called a spectrum. The component with the lowest frequency is called the fundamental frequency, which gives the sound its characteristic pitch. o Determines the pitch of the complex sound Harmonic frequencies are components of sound that have a frequency that is an integer multiple of the fundamental frequency o Operate to demonstrate the differences in the timbre or quality of the sound

Spectrum of Musical Instruments

Fourier Analysis  

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Definition: to decompose a complex sound into its frequency (sinewave) components This ‘decomposition’ is usually displayed visually in a spectrogram – a graphical representation of changes in the frequency content of a signal over time Time is plotted horizontally, frequency is plotted vertically, and amplitude is represented by the darkness of the plot Time is plotted horizontally, frequency is plotted vertically, and amplitude is represented by the darkness of the plot

Spectrogram of Speech  

Time is plotted horizontally, frequency is plotted vertically, and amplitude is represented by the darkness of the plot Far more complex than simple sine waves!

Fourier Filters 

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Filters separate things on the basis of a given property o E.g., A coffee filter separates things on the basis of particle size o Let us the liquid through (small particles), but “filters out” the granules (large particles) o “Low-pass filter” (Only let’s in particles in less than the cut-off) Fourier filters allow certain frequency components of a sound to pass while blocking others

o o o

E.g., Sound travelling pass the head Head obstructs high frequencies, thus acts as a low-pass filter E.g., Bass/treble settings, graphic equalizers

Linear/Non-Linear Filters 

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In order to apply Fourier theory, we assume the filter is linear (i.e. it follows 3 rules) 1. Output of a filter must not contain any frequency which was not present in input 2. If amplitude of the input is changed by some factor, the output must also change by the same factor 3. Total output of multiple signals (A, B, C) must be equal to the output of A + B + C Filters that violate these assumptions are called nonlinear filters. They often add distortions to a signal such as additional frequency components.

Is the Ear a Fourier Analyser ? 

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Maybe… o Auditory filters separate frequencies into different ‘channels’ o Responds to amplitude within each channel o Can encode phase information But not quite… o Due to non-linearities between the input and the output o 2 tones should result in two peaks, but often 3 peaks merge o Outer hair cells amplify small intensities

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The Ear 

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3 parts o Outer Ear o Pinna, Meatus Middle Ear o Ossicles o Tympanic Membrane (ear drum) Inner Ear o Cochlea

Physiology: The Ear  

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The Outer & Middle Ear Outer Ear o Pinna: the flexible flap on the outside of the ear. o Focuses sound waves into the ear canal (meatus). o Shape & size of outer ear have the effect of amplifying medium sound frequencies (1500-7000 Hz). Middle Ear

o

The small bones (ossicles) in the middle ear transmit sound energy from the eardrum (tympanic membrane) to the oval window in the inner ear.

The Inner Ear     

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The inner ear contains a small, coiled tube (cochlea), filled with fluid. Cochlea, basilar membrane, Cano receptors The oval window is situated at one end of the cochlea. The cochlea is divided in two along its length by the basilar membrane. Sound waves impinging on the oval window displace fluid along the cochlea & cause a travelling wave along the basilar membrane. Movement is at the same frequency as the sound wave

Transduction: Inner Hair Cells (Organ of Corti)    

3500 inner hair cells protrude from the basilar membrane. Fluid displacement causes vibration in basilar membrane This deflects the stereocilia of inner hair cells, generating impulses The base of each inner hair cell makes contact with afferent fibres of the auditory nerve (50,000 nerve fibres).

Frequency-to-Place Conversion in the Cochlear 

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The fluid displacement in the cochlear takes the form of a wave travelling along the basilar membrane. The wave peaks at a particular location, due to the width & stiffness gradient along the basilar membrane. High frequencies show largest vibration near the stapes, at the base of the cochlea Low frequencies show the largest vibration near the apex of the cochlea This is known as ‘frequency-to-place conversion

Inner Hair Cells: Place and Frequency Codes 

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Place code o Hair cells have a "characteristic frequency" to which they respond best, determined by the part of basilar membrane to which they are connected. o Sound frequency can be encoded by the region of basilar membrane to which the most active cell is attached. Frequency (rate) code o Inner hair cell impulses are timed to coincide with a certain phase of the wave (“phase locking”), at least for low frequencies o So, the response rate of a particular nerve fibre should reflect the frequency of the signal.

Inner Hair Cells: Coding Intensity    

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The range of sound levels over which human hearing can operate (its dynamic range) is >100 dB. Individual auditory nerve fibres have a dynamic range of only 20-60 dB. Dynamic range = difference between minimum intensity (sound pressure level) to which a fibre response, and the intensity at the fibre’s maximum firing rate In order to cover the full dynamic range of human hearing, two groups of auditory fibres have different roles: High spontaneous rate fibres respond to lower sound intensities. Low spontaneous rate fibres respond to higher intensities.

Auditory Nerve and Characteristic Frequencies     

Nerve cells send signals along the auditory nerve toward the brain Auditory nerve fibres respond best to particular “Characteristic frequencies” These correspond to their hair cell’s position ...