Lecture 1 - Perception

Question 1

what is sensation?

Answer 1

is directly linked to our senses. It’s the process of taking information through receptors, which then translates it into signals that the brain interprets as images, sounds, smells, and other sensory experiences

Question 2

What is perception?

Answer 2

involves an extra step. Involves the interpretation and understanding of sensations

Question 3

How does variability in perception cause disagreements?

Answer 3

• Disagreements highlight the variability in perceptual outcomes and are not simply due to differences in skill or attention
• Under ‘easy’ conditions, perception is reliable but when conditions are ‘not ideal’, responses become probabilistic
• Perceptual judgments are not always perfect

Question 4

Key facts about perception

Answer 4

• Perception (e.g. vision) is not simply a passive registering of info about the world (like a camera). It’s an active process of interpretating sensory info to guide our interactions with the environment
• Because perception appears ‘easy’, it’s also easy to fall into the trap of believing that there is nothing to explain
• Perception feels ‘easy’ because we have so much specialised ‘neural circuitry’ devoted to processing sensory info (30 areas)

Question 5

Why understand perception? 6 reasons

Answer 5

• Understand the brain and cognition and how sensory inputs are processed and transformed into a conscious experience
• Improve Human-Technology Interaction (HCI) to inform the design of user-friendly technologies
• Enhance medical diagnosis and treatment
• Advance Artificial Intelligence (AI)
• Improve education and learning
• Understand and improve everyday experiences to optimize usability, safety and aesthetics

Question 6

Approaches to studying perception: Psychophysics

Answer 6

• The study of the quantitative relationship between sensory experience (‘psycho’) and environmental stimulation (‘physics’)
• Oldest branch of experimental psychology based on the ideas of Weber (1834) and techniques developed by Fechner (1860)
• Subjects report when he/she detects the presence of a sensory stimulus. Measures the perceptual performance of the entire organism
• The central concept is the measurement of thresholds (limits of perception)
• Detection threshold: the weakest stimulus that reliably evokes a sensation in the observer
• Discrimination threshold: the smallest difference between 2 stimuli along a particular dimension that can be detected
• Infer properties of perceptual mechanisms from changes in thresholds
• Limits: change stimulus strength until the subject says just detectable
• Constant stimuli: present the subject with a fixed set of stimulus strength in random order and ask them each time whether they detect it

Question 7

what is Signal Detection Theory?

Answer 7

for the SAME stimulus, the subjects sometimes response correctly and sometimes incorrectly. Sensory systems are imperfect and inherently ‘noisy’. This internal noise interferes with our perceptual decisions about the world when the stimulus is weak. Bias also plays a role. 75% correct

Question 8

Approaches of studying perception: Electrophysiology

Answer 8

• Recording the electrical activity of cells in sensory pathways (single cell recording)
• Extracellular recording from single cells in sensory areas of brain are commonly used to study perceptual apparatus
• Technique used to determine a cell’s preferred stimulus by recording action potentials elicited by a range of visual stimuli
• Very fine-tipped wire is surgically placed into the area of the visual system under stuff
• The microelectrode tip is slowly positioned next to the axon of a cell so that it picks up action potentials ideally from only that cell
• The weak electrical signals are then amplified and then recorded
• Enables the experimenter to map the cell’s preferences
• Peri- stimulus-time-histogram (PSTH): is a plot showing how the firing rate of a cell changes during the time a stimulus is presented within its receptive field
• Limitations: tells us little about perceptual processes which rely on the combined activity of many neurones

Question 9

Approaches of studying perception: Neuroimaging

Answer 9

• EEG or electroencephalography: electrical activity generated by neurons is picked up the electrodes positioned on the scalp
• The electrical activity is very small and needs to be amplified then recorded
• EEG will record the activity of a large group of neurons, so it’s less precise to single unit
• We can present stimuli and evaluate how the brain processes them

Question 10

Approaches of studying perception: Neuropsychology

Answer 10

• Functional magnetic resonance imaging (fMRI): takes a picture of which areas are more active
• Tales some time (2-3 seconds) so we know where things are happening