Unit 5: Sensation & Perception (Chapter 4) Flashcards
Colour
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.
Colour constancy
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.
Sensation
Raw data; process by which sensory organs detect environmental stimuli & convert them (though transduction) into electrical signals for the nervous system.
Stimulus
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)
Transduction
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.
Perception
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
Psychophysics
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.
Absolute threshold
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.
Signal detection theory
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.
Signal detection theory terms (in relation to radiologist example)
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
Liberal bias
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.
Conservative bias
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.
Alive or not? study
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.
Just-noticeable difference/difference threshold
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.
Weber’s law / Weber’s fraction
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.
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?
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
Adaptation
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).
Vision
Processing of light reflected from objects.
Visible light
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).
Wavelength (Vision)
Distance betweem successive peaks. Decoded as colour. Inversly related to frequency.
Frequency (Vision)
Number of cycles per second. Inversly related to wavelength.
Amplitude (Vision)
Height of the wave. Decoded as brightness.
Cornea
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.
Iris
Opaque, colourful muscle encircling the pupil. Can increase or decrease size of pupil, determining how much light enters (by contracting, expanding).