Lectures Perception and cognition
Week 1
Lecture 1
Sensory information is reaching your brain and that leads to a subjective experience.
We rely on our sensory input for all information about our external environment. Our brain
builds our perception of the world with only our senses. There is no way to check if our
perception is real.
The input for perception is the sensory information. The output is our percept. In
experiments we manipulate the input and measure the output. The brains is the black box.
We are trying to understand the process in the brain.
Stages of perceptual processing;
1. Environmental stimuli (light)
2. Sensory receptors ( eg. Rodds in the eyes)/ transduction
3. Neural coding (neural impulses)
4. Perceptisl experience
,Transduction; conversion of a physical energy or chemical signals into neural signals.
Neural coding; passing signals between brain regions.
Signal detection theory; you are in the shower. You hear something. You can hear the shower
noise alone OR the ringrone of your phone and the shower noise.
Criterion; the point were you decide the phone is ringing so you step out of the
shower.
Correct rejection; you don’t hear the phone when the phone isn’t ther
Hit; you hear the phone and go out of the shower
False alarm; you thought you heard your phone but it wasn’t.
Miss; you didn’t hear the phone while it was tinging.
Using hits and false alarms allow us to dissociate sensitivity and criterion
No sensitivity; you can’t discriminate between the sound of the shower and the
phone.
You can use the signal detection theory for e.g. sound localization/ facial identification
,A. You expect an important phonecall so you are willing to tolerate a larger number of
false alarms in order to make sure that you absolutely minimise the numer of misses.
C. you ar really enjoying the shower. And you want to avoid the possibility that you stop
your shower early to answer it. So you ONLY decide to answer the phone if you have
compelling evidence that the phone is ringing
Sensitivity; measure of how distinct these two distributions are. Sensitivity is usually
conceptualised as the speration between the noise and signal plus noise curves; greater
the seperation, greater the sensitivity.
Onderste A. you have an equal chance of hearing the shower nois along or the ringtone
plus noise
Onderste C. you can place your criterion that you have very few alarms and few misses.
, The relationship between light
wavelength/intensity (input) and the likelihood of a cone absorbing a photon (output) is well-
characterized. If the m- cone is responding more than the l- cone the light will be greenish.
- If L-cone responds more, light is more likely to be reddish.
- If M-cone responds more, light more likely to be greenish.
- If response is similar/same light likely to be yellowish or bluish
Main characteristics of perception;
1. Cognitive impenetrability; routinely, explicit knowledge of image’s structure does not
influence it’s perceived properties; eg. Sheppards table illusion
Week 1
Lecture 1
Sensory information is reaching your brain and that leads to a subjective experience.
We rely on our sensory input for all information about our external environment. Our brain
builds our perception of the world with only our senses. There is no way to check if our
perception is real.
The input for perception is the sensory information. The output is our percept. In
experiments we manipulate the input and measure the output. The brains is the black box.
We are trying to understand the process in the brain.
Stages of perceptual processing;
1. Environmental stimuli (light)
2. Sensory receptors ( eg. Rodds in the eyes)/ transduction
3. Neural coding (neural impulses)
4. Perceptisl experience
,Transduction; conversion of a physical energy or chemical signals into neural signals.
Neural coding; passing signals between brain regions.
Signal detection theory; you are in the shower. You hear something. You can hear the shower
noise alone OR the ringrone of your phone and the shower noise.
Criterion; the point were you decide the phone is ringing so you step out of the
shower.
Correct rejection; you don’t hear the phone when the phone isn’t ther
Hit; you hear the phone and go out of the shower
False alarm; you thought you heard your phone but it wasn’t.
Miss; you didn’t hear the phone while it was tinging.
Using hits and false alarms allow us to dissociate sensitivity and criterion
No sensitivity; you can’t discriminate between the sound of the shower and the
phone.
You can use the signal detection theory for e.g. sound localization/ facial identification
,A. You expect an important phonecall so you are willing to tolerate a larger number of
false alarms in order to make sure that you absolutely minimise the numer of misses.
C. you ar really enjoying the shower. And you want to avoid the possibility that you stop
your shower early to answer it. So you ONLY decide to answer the phone if you have
compelling evidence that the phone is ringing
Sensitivity; measure of how distinct these two distributions are. Sensitivity is usually
conceptualised as the speration between the noise and signal plus noise curves; greater
the seperation, greater the sensitivity.
Onderste A. you have an equal chance of hearing the shower nois along or the ringtone
plus noise
Onderste C. you can place your criterion that you have very few alarms and few misses.
, The relationship between light
wavelength/intensity (input) and the likelihood of a cone absorbing a photon (output) is well-
characterized. If the m- cone is responding more than the l- cone the light will be greenish.
- If L-cone responds more, light is more likely to be reddish.
- If M-cone responds more, light more likely to be greenish.
- If response is similar/same light likely to be yellowish or bluish
Main characteristics of perception;
1. Cognitive impenetrability; routinely, explicit knowledge of image’s structure does not
influence it’s perceived properties; eg. Sheppards table illusion
