Lecture 2 - Sensation 1 Flashcards
What is Sensation?
The detection of external stimuli and the transmission of this information to the brain
What is Perception?
The processing, organization, and interpretation of sensory signals - not necessarily conscious interpretation
What is Bottom-Up Processing?
Perception based on the physical features of the stimulus
What is Top-Down Processing?
How knowledge, expectations, or past experiences shape the interpretation of sensory information
What is the difference between Sensation vs Perception?
The sensory information provided is
relatively constant (Sensation)
BUT
What is seen/perceived is very
variable (Perception)
What is Sensory Coding?
Sensory receptors translate the physical properties of stimuli into patterns of neural impulses.
What is Transduction?
The process by which sensory stimuli are converted to signals the brain can interpret
What type of information does the brain need about a stimulus to perform transduction?
The brain needs qualitative and quantitative information about a stimulus.
> Qualitative information consists of the most basic qualities of a stimulus.
> Quantitative information consists of the degree, or magnitude.
How does the brain know what the neural activity indicates (e.g., light, pain etc)?
Anatomical Coding and Temporal Coding
What is Anatomical Coding?
The receptors (e.g., in the eye, ear etc) are connected to specific parts of the brain - when those parts of the brain are activated, the source of stimulation is clear
» sensations are coded by what is active
What is Temporal Coding?
Different stimulation gives rise to different rates of activity in the receptor - e.g., When bright vs low light
» intensity of sensation is coded by rate of activity
What is Qualitative Information in sensation?
Sensory receptors respond to qualitative differences by firing in different combinations
What is Quantitative Information in sensation?
Sensory receptors respond to quantitative differences by firing at different rates
What is the Absolute Threshold?
The minimum intensity of stimulation
that must occur before you experience a sensation.
What is the Difference Threshold?
The minimum amount of change required for a person to detect a difference between two stimuli
What is Weber’s Law?
The Just Noticeable Difference (jnd) between two stimuli is based on a proportion of the original stimulus rather than on a fixed amount of difference
E.g. if A = 100g and B = 105g, the JND = 5g
If A = 200g and B = 210g, the JND = 10g
If A = 300g and B = 325g, the JND = 25g
How to detect the Absolute Threshold?
The level of intensity at which participants correctly detect a stimulus on 50% of trials in which it is presented is the Absolute Threshold.
What is the Just Noticeable Difference?
The smallest difference between two stimuli that is observable
What is Signal Detection Theory (SDT)?
A theory of perception based on the idea that
the detection of a stimulus requires a judgment and is not an all-or nothing process
How is Signal Detection Theory researched?
Signal detection research involves a series of trials in which a stimulus is presented in only some trials. In each trial, the participant must state whether he or she sensed the stimulus.
What is Sensory Adaptation?
A decrease in sensitivity to a constant level of stimulation
If a stimulus is presented continuously, the responses of the sensory systems that detect it tend to diminish over time - when a continuous stimulus stops, the sensory systems usually respond strongly as well
How many methods for threshold measurement are there?
Fechner originated 3 methods for threshold measurement; The method of limits, the method of constant stimuli, and the method of adjustment
What does the Method of Limits record?
Difference or absolute thresholds
What does the method of constant stimuli record?
Difference and absolute thresholds
What does the method of adjustment record?
Difference thresholds
How does the method of limits work?
Stimulus intensity is increased/decreased until the subject starts/stops sensing the stimulus
How does the method of constant stimuli work?
Stimulus intensity is varied in fixed steps across a circumscribed range
How does the method of adjustment work?
Stimulus intensity is changed by the observer until they see it differ or be indistinguishable from a comparison stimulus
> Stimuli either start the same and are changed to differ, or start different and are changed to be the same
