Week 1 : Introduction

Question 1

Why is this psychology?

Answer 1

• the goal is to understand perceptual experience, how our brains make sense of the sensory world around us
• understanding how our minds, through our brains, interpret the world around us in an inherently psychological goal
• lastly, psychological processes (like attention, intention, emotion & biases) influence the ways in which we perceive the world

Question 2

Why study perception at all?

Answer 2

• Creating an analog perception of the world through a digital signal
• human perception greatly improves all processes in the social world

Question 3

Bottom-up & top-down flow of information

Answer 3

Perception represents a combination of bottom-up processes (shape, colour, motion) with top-down information that arises from cognitive processing of a stimuli (predictions, theory, knowledge, context)

Question 4

The senses…

Answer 4

1. vision
2. hearing
3. smell (olfaction)
4. taste (gustation)
5. light touch
6. pressure
7. cold
8. heat
9. pain
10. itch
11. vestibular
12. proprioception

Question 5

Sensation…

Answer 5

• refers to the registering of a physical stimulus on our sensory receptors
• sensation changes physical stimuli into information in our nervous system
• about stimuli

Question 6

Perception…

Answer 6

• refers to the later aspects of the perceptual process which involves turning the sensory input into meaningful conscious experience
• the translation of the neural signal into useable info
• perception occurs after cognitive processing begins, typically in the cerebral cortex
• about interpretation

Question 7

transduction & neural responses

Answer 7

• for each of our sensory systems, we have specialized neural cells called receptors that transduce (transform) a physical stimulus into an electrochemical signal… called a neural response & sent to the brain
• this is how stimuli the outside world becomes perceptual experiences
• sensation = transduction & perception = guide functional action

Question 8

Phenomenology…

Answer 8

• our subjective experience of perception
• refers to our internal experience of the world around us
• unique creation of the living brain

Question 9

history of sensation & perception

Answer 9

• Writings on disorders of sensation and perception go back all the way to the ancient Egyptian
• Aristotle theorized extensively about perception and its causes (motion aftereffect/waterfall illusion & touch between tips of fingers)
• Later in the 19th century, German physiologists began experimenting on the neural processes that underlie sensation, and others started the field of psychophysics
• Later influences in the development of sensation and perception research include gestalt psychology, Gibsonian direct perception, information processing and the computational approach.
• Neuroscience also addresses issues of sensation and perception.
• Neuroscience research includes single-cell recording, neuropsychology and neuroimaging.

Question 10

Helmholtz…

Answer 10

• the first person to determine the speed of the neural impulse (or action potential)
• developed the concept of the trichromatic theory of colour vision
• developed a general theory of how our senses work & argued that the info from the sensory signal itself is inadequate to explain perception, so the signal needs to be interpreted by active cognitive process… so we must incorporate info from existing knowledge to completely perceive the world
• called unconscious inference
• work influences information processing and computational approach

Question 11

Hering…

Answer 11

• opponent-process theory
• thought that environmental inputs and our sensory systems are sufficient for us to grasp the structure of the perceived world
• influences gestalt psychology & direct perception theory

Question 12

Weber…

Answer 12

• Weber’s law states that a just-noticeable difference (JND) between two stimuli is related to the magnitude/strength of a stimuli
• concerned w the perception of difference between 2 stimuli
• it is harder to distinguish between 2 samples when they are larger/stronger levels of stimuli

Question 13

Fechner…

Answer 13

• founder of psychophysics = the study of the relation between physical stimuli and perception
• fechner colour effect = moving black-and-white figures create an illusion of colour
• fechner’s law = states that sensation is a logarithmic function of physical intensity… our perception of the intensity of a stimulus increases at a lower rate than does the actual intensity of the stimulus

Question 14

psychophysical approach

Answer 14

• seeks to understand how the physical properties of a stimulus affect its perception
• This is often done by measuring by how much a particular stimulus property must be changed in order for that change to be noticeable (Weber)
• absolute threshold, JND

Question 15

direct perception (Gibsonian approach)

Answer 15

• the world generates so much information that the senses only need to pick it up directly
• emphasizes ecological realism in experiments

Question 16

Information-processing approach

Answer 16

• approach says perceptual & cognitive systems can be viewed as the flow of info from one process to another
• information is collected by sensory processes & then it flows to a variety of modules that decode info, interpret it & allow the organism to act on it
• each of the stages takes a finite amount of time, and therefore these processes can be observed or measured by recording reaction times

Question 17

Computational approach

Answer 17

• studies perception by trying to specify the necessary computations the brain would need to carry out to perceive the world
• heavily influenced by growth of comp sci and AI
• sought a mathematical explanation for perceptual processes (esp vision)
• often more theoretical, focusing on modelling perception

Question 18

Microelectrode

Answer 18

• one of the most important developments in neuroscience
• device so small that it can penetrate a single neuron in the mammalian central nervous system without destroying the cell & record activity
• this method allows the recording of behaviour of a single neuron & can be used to determine what stimuli it responds to
• Hubel & Wiesel

Question 19

neuropsychology…

Answer 19

the study of the relation of brain damage to changes in behaviour

Question 20

Agnosia…

Answer 20

• deficit in some aspect of perception as a result of brain damage

Question 21

cognitive penetration**

Answer 21

• the view that cognitive and emotional factors influence the phenomenology of perception
• means that nonperceptual factors affect what we see, hear, feel and taste
• cognitive impenetrability is the opposite and says perception is not affected by cognitive factors - this is the dominant view saying that perception remains the same regardless of cognitive/emotion state & what changes instead is our attention, expectation/mood state

Question 22

psychophysical scale

Answer 22

• a psychophysical scale is one in which ppl rate their psychological experiences as a function of the level of a physical stimuli
• involve presenting a controlled stimulus to participant & asking them questions that allows the answer to be quantified
• focus on the relation between physical properties & perception
• detection test, comparison test, a magnitude test or a preference scale

Question 23

Method of limits

Answer 23

• stimuli are presented on a graduated scale & participants must judge the stimuli along a certain property that goes up/down
• researcher hopes to pick an extreme value that’s readily detected & a level that is never detected & then several levels between them
• used to determine both absolute & different thresholds

Question 24

Absolute threshold

Answer 24

• the smallest amount of a stimulus necessary to allow an observer to detect its presence
• To determine an absolute threshold with the method of limits, researcher use an ascending series and a descending series
• ascending series = stimulus gets increasingly larger
• descending series = stimulus gets increasingly smaller

Question 25

Difference threshold (JND)

Answer 25

• the smallest difference between 2 stimuli that can be detected
• the smallest difference in weight that can be detected is the difference threshold, equal to 1 JN

Question 26

Crossover point

Answer 26

• the point at which ppl change from detecting to not detecting or vice versa
• the threshold will be different when measured by ascending vs descending methods
• researchers typically average these to get their best estimate of the absolute threshold

Question 27

method of constant stimuli

Answer 27

• in the method of constant stimuli, the threshold is determined by presenting the observer with a set of stimuli, some of which are above the threshold and others below it
• the stimuli are presented in a random order
• all stimuli presented & all are selected beforehand
• prevents observer from being able to predict/anticipate what the next will be
• time consuming & requires many trials
• stimulus detected 50% of time and not detected 50% of time is considered the threshold
• used by audiologists

Question 28

Method of adjustment

Answer 28

• the observer controls the level of the stimulus and ‘adjusts’ it to be at the perceptual threshold
• participants increase or decrease the level of the stimulus until if feels as if it is at just the detectable level
• very quick, but leads to greater variance from participant to next
• useful for matching one stimulus to another to determine the point of subjective equality (PSE)… which designates the setting of 2 stimuli at which the observer experiences them as identical

Question 29

Magnitude estimation

Answer 29

• a psychophysical method in which participants judge & assign numerical estimates to the perceived strength of a stimulus
• in all sensory systems there is response compression… as the strength of a stimulus increases, so does the perceptual response, but the perceptual response does not increase by as much as the strength of the stimuli increases
• (e.g. doubling sugar in something doesn’t mean we think its 2x as sweet)
• exception to this is in pain perception & it has response expansion instead

Question 30

Steven’s power law

Answer 30

• encapsulates response expansion & compression
• P = cI^b
• p = perceived magnitude of stimulus
• I = intensity of the actual stimulus
• c = represents a constant which allows you to scale your measure appropriately
• b = the power to which the intensity is raised… it is this exponent that allows response compression & response expansion
• response compression occurs when b<1 and response expansion occurs when b>1

Question 31

catch trials

Answer 31

• participants may willingly/unwillingly misinform experimenter about perceptual experience, so we have catch trials
• they are trials in which the stimulus is not presented at all which checks on the participants accuracy & honesty
• another thing is the forced-choice method when the subject is asked to report either when the stimulus occurred or where it occured

Question 32

Signal detection theory…

Answer 32

• the theory that in every sensory detection or discrimination, there is both sensory sensitivity to the stimulus and a criterion used to make a cognitive decision
• Mistake = false alarm/miss
• right = correct rejection/hit
• the differing judgment of the basis of situation is called the criterion… which is an internal cut-off determined by the observer, above which the observer makes one response and below which the observer makes another response
• criterion is a bias that can affect the rate of hits and false alarms & based on situation & only observer knows
• Sensitivity in signal detection theory is the ease or difficulty with which the observer can distinguish the signal from noise
  It measures how easy it is to
• In psychophysics, if you know the relation of hits to false alarms, you can determine d^I (d prime)… a mathematical measure of sensitivity
• The summary of all of this on a graph is called the receiver-operating characteristic (ROC) curve
• The ROC curve is a graphical plot of how often false alarms occur versus how often hits occur for any level of sensitivity
• Sensitivity or (d^I) is captured by the ‘bow’ of the curve (the more the curve bends up to the right, the better the sensitivity)
• Moving along the bow captures the criterion

Question 33

2 goals of neuroimaging

Answer 33

1. reveal where perception happens in the brain
2. how perception unfolds thru the brain over time

Question 34

electroencephalography (EEG)

Answer 34

• Up to 128 electrodes positioned on scalp
• electrodes detect electrical signals created by the brain
• It picks up a continuous electric signal, which allows for measurements to be made every millisecond
• It allows for determining the time course of perceptual processes in the brain

Question 35

Magnetoencephalography (MEG)

Answer 35

• Magnetic sensors detect small magnetic fields produced by the electrical activity in the brain
• Detects rapid changes in the brain (less precise time scale than EEG)
• Produces better spatial maps of the brain than EEG but not as good as MRI
• less portable & way more expensive

Question 36

Magnetic resonance imaging (MRI) and functional magnetic resonance imaging (fMRI)

Answer 36

• Large magnetic fields align the oxygen molecules within the brain
• Takes pictures approx. every 30 milliseconds
• Allows scientists to pinpoint both where and over what time course perceptual processes are happening in the brain
• Very detailed images of the brain structures involved in perceptual processes

Question 37

transmagnetic stimulation (TMS)

Answer 37

• Stimulate the brain via electric current
• Researchers place a magnetic field generator (or coil) on the head of participants
• The coil induces an electric current in the particular brain region beneath the coil which induces changes in hoe this region functions