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Chapter 1

Chapter 1 Book notes


Department
Psychology
Course Code
PSYB51H3
Professor
Matthias Niemeier
Chapter
1

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PSYB51: Chapter 1: Introduciton
Introduction:
Plato:
Compares our ordinary sense of reality to that of prisoners in a cave.
Plato paints this imaginary picture to emphasize how critically our conception of reality depends
on what we can learn about the world through our senses.
Everything you think is true about the world around you depends on what you can learn through
your eyes ears nose tongue and skin.
Platos picture basically stated that your understanding of reality and even your sense of
imagination is restricted to those things that you can perceive through your senses
Heraclitus:
you can never step into the same river twice”-> basically saying everything is constantly
changing
This is also true for our perceptual experiences
This is true because
Every experience changes the following experience.
Perception quickly comes to ignore anything that stays the same for a very long time.
Adaptation:
A reduction in response caused by prior or continuing stimulation
All of our sense adapt to constant stimulation.
Democritus:
Had complete trust in sense:
The world is made up of atoms that collide with one another
Psychophysical methods:
Method of constant stimuli:
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PSYB51: Chapter 1: Introduciton
Method requires creating many stimuli with different intensities in order to find the
tiniest intensity that can be detected.
Example:
o A hearing test, theres a certain threshold hold level when you can hear and you
can hear tones. The absolute threshold level is when you can hear the sound 50%
of the time.
Method of limits:
This is a more efficient approach rather than the method of constant stimuli.
In this method the researcher starts off with the same set of stimuli but instead of the random
presentation the tones are representing in order of increase or decreasing intensity.
The data that is collected from is skewed, because it was found that when sounds are increasing in
intensity it will take a higher intensity to report the hearing of the tone
So what researchers do is that they take the point at which the person reports as not being able to
hear the sound while decreasing and the point at which the person reports that they hear the sound
while it is increasing. And take that average and the is reported as the threshold.
Method of adjustment:
This is like the method of limit except the subject is the one who steadily increase or decrease the
intensity of the stimulus.
This is the easiest method to understand, it is like turning the volume down on a radio or
decreasing the light luminances on a blub.
However, its the least used in measuring thresholds.
Signal detection theory:
Thresholds tend to change from trial to trial maybe that subjects change from trial to trial .
Our auditory and visual systems actually create energy or noise.
oExample when you plug your ears you still hear some noise in the background.
When you close your eyes in dark room you still tend to see grey and a
flashes,
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PSYB51: Chapter 1: Introduciton
When your are trying to detect a faint sound or flash of light, you must detect it above and beyond
any activity going on in your head in the first place.
The main factor is that : your perceptual task is to detect the signal in the presences of the noise.
oSo theres a noise alone distribution
oTheres a noise and sound distribution
Both of these are to be processed by the brain so that they can tell the difference.
So say a phone rings there are technically 4 possible out comes:
1. You might say no when there is no ring that is a CORRECT REJECTION
2.You might sat yes when there is a ring that is a HIT
Then there are errors:
1. If you jump out of the shower when there is no ring then that is a FALSE ALARM
2.IF YOU MISS THE CALL THEN THATS A MISS.
By knowing the relationship of hits and false alarm you can calculate the sensitivity measure known as
d’( D PRIME)
For a fixed value of d’ , changing the criterion changes the hits and false alarms in predictable
ways.
If you plot hits against false alarms for different criterion values you get a curve called the
RECIEVER OPERATING CHARACTIERISC CURVE( ROC)
oReceiver operating characteristics ( roc)
In studies of signal detection the graphical plot of the hit create as a function of
the false alarm rate. If these are the same ,points fall on the diagonal , indicating
that the observer cannot tell the difference between the presence and absence of
the signal. As the observers sensitivity increases, the serve bows upward towards
the upper left corner. The point represents a perfect ability to distinguish signal
from noise
oSignal detection theory:
The body of research that studies the detection of signal in noise in this manner
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