Sensation & Perception Flashcards
Ernst Weber Published what book?
De Tactu–> investigation of muscle sense
De Tactu by Weber introduced what notion?
Just noticeable difference in sensation–> one JND needs to be added/subtracted from stimulus for person to say he notices the difference
Gustav Fechner discovered what relationship?
Relationship between physical stimuli + psych response to stimuli
Francis Galton was interested in what field of study?
Individual differences. Measuring the sensory abilities of 10,000+ people
Max Wertheimer founded what school of psychology? + believed what about studying conscious experience?
Gestalt psychology. An analysis of experience into parts is not a valid way of studying conscious experience
Psychophysics is concerned with measuring what?
The relationship between physical stimuli + psych response to stimuli
What are the two main types of thresholds in sensory perception?
Absolute threshold + difference threshold
What is absolute threshold?
Minimum amount of stimulus that person can perceive + stimulus energy needed to activate a sensory system. E.G to taste, need 1 tsp of sugar dissolved in 2 gallons of water.
Another word for threshold is what?
Limen. Hence the term sub-limen-al
What is subliminal perception?
Perception of stimulus below the threshold of conscious awareness. Has little value in selling products.
What is a difference threshold?
Refers to how different to stimuli must be in magnitude before a difference between them is perceived.
How is difference threshold examined?
By comparing a standard stimulus to a comparison stimulus that is different in value.
What is a just noticeable difference?
JND Measures the same thing as difference threshold but in diff units. It is the amount of change required to predict diff btw two stimuli.
Weber’s law formulated by Fechner claims what?
What is important in producing a JND is not the absolute diff btw two stimuli, but the ratio of them
What is Weber’s fraction?
S/S or I/I =K where K is the constant
What does Fechner’s law express?
The relationship btw intensity of sensation + intensity of stimulus.
Sensation increases more slowly as intensity increases.
Which scientist suggested that Fechner’s law might be incorrect?
S.S Stevens, who came up with Steven’s power law instead.
What is signal detection theory?
Suggests that other, non-sensory factors influence what subjects say they sense. E.G experiences, motives, expectations play a role.
Cautious person wants to make sure they actually heard a tone VS paranoid person always being sure they heard it.
Signal detection theory controls for which two factors?
1) How well the subjects can sense the stimulus
2) response bias due to non-sensory factors
What happens in basic signal detection experiments?
1) two situations: stimulus presented/not presented
2) when not presented: noise trial, where sensory system still gets excited by random firings in nervous system in absence of stimulus
3) when presented: signal trial
What are the four possible outcomes of signal detection experiments?
1) signal present- “yes it is”- Hit
2) signal present- “it’s not”- Miss
3) signal not present- “it is”- false alarm
4) signal not present- “it’s not”-correct negative
What are receiver operating curves ROCs? Who refined these curves?
Used to graphically summarize a subject’s responses in a signal detection experiment. John A Swets refined their use.
The first step in all sensory info processing is what?
Reception. Each sensory system has receptors to react to physical external energy.
The second step in all sensory info processing is what?
Transduction. The translation of physical energy into neural impulses/action potentials.
The third step in all sensory info processing is what?
Projection. Electrochemical energy is sent to projection areas in the brain along neural pathways in order to be processed by nervous system.
Name the 5 structures of the eye + their function
Cornea-> clear, dome window. Gathers + focuses incoming light
Pupil->hole in iris. Contacts/expands to let light in/keep out
Iris->coloured part. Controls size of pupil + amount of light entering eye thru involuntary muscles
Lens-> behind iris. Control light curvature + focus near/far objects on retina
Retina->back of the eye. Detects images
Duplicity theory of vision states what?
Retina contains two types of photoreceptors. Light passes through sensory neurons before stimulating the photoreceptors.
What is the blind spot?
Where the optic nerve leaves the eye, and no photoreceptors exist.
What is the function of Cones + when is it most effective?
Most effective in bright light.
used for colour vision: chromatic + achromatic colours, as well as perceiving fine detail
What is the function of rods!+ when is it most effective?
Most effective in low illumination.
Not involved in colour vision + only perceive achromatic colours. Low sensitivity to detail.
There are many more — then —in human eye, except for the fovea at the centre that contains only —. But there are more — at the periphery.
More rods, less cones, fovea contains only cones so has best visual acuity + most sensitive to daylight vision. Rods at periphery
What do rods and cones connect with in the optic nerve?
Connect with several layers of neurons such as horizontal, amarcrine, bipolar, and ganglion cells. (HABG)
Describe why cones have greater sensitivity to detail?
Rods and cones connect with bipolar neurons–> connect to ganglion cells–> group to form optic nerve–> represent combine activity of many rods and cones–> loss of detail as info from photoreceptors is combined
On average, number of cones converged onto individual ganglion cells is —than the number of rods.
Smaller. Which is why they have higher detail sensitivity
The image of stimulus on right side of visual field forms on the — half of each eye’s retina. The image on the —side of visual field forms on the right half of retina.
Left, left
In the optic chiasm, do the fibres cross paths?
Yes, near the nose, the fibres from left eye go to right side of brain, the fibres from right eye go to left side of brain.