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Lecture 4

PSYC 1001 Lecture Notes - Lecture 4: Sound, Retina, Central Nervous System

Course Code
PSYC 1001
Ayca Guler- Edwards

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Introduction to the Study of Psychology PSYC1001 – Section B
February 15, 27 & March 1, 2018
Goals for today’s class… How we start impulse, the way that happened, shapes the way we think about
Chapter 4
How do we detect and process information from our environment?
How are environmental stimuli received and turned into neural patterns?
Sensation & Perception
In order to survive, organisms need to “know” the world around them.
The primary function of our sense organs is to provide information that can guide behaviour.
The way this information is transmitted and processed, influences the way we perceive,
interpret, and think about, the world around us.
Sensation & Perception
Sensation – the detection of simple properties of stimuli (without making “sense” of them – i.e.
no perception or interpretation) Transfer environment to our neuron impulse.
Distal Stimulus – the stimulus in the environment (I am a distal stimulus to you). The
thing in the environment.
If you reading the screen, the screen is distal stimulus.
Proximal Stimulus – the stimulus as it is stimulating our sense receptors (the “image” of
me that is being projected onto the back of your retina, and the sound waves that are
vibrating your auditory hair cells are the proximal stimuli).
Stimulus activating your sense of cells. Actual stimulus in your sensory cell, like
your skin, you got pressure, temperature, the sensory cell display in your skin.
Sensation & Perception
Perception – the detection of more complex properties of stimuli (i.e. it’s meaning) – this
involves learning. Wrap it, automatically serious of impulse.
Perception is a rapid, automatic, unconscious process where we recognize what is represented
by the information provided by our sense organs.
Perception Involves Processing: We are imposing meaning, there are two kinds of processing.
Bottom-up Processing – examining each of the components of the environmental stimulus first,
and then synthesizing the whole. When you looking at the visual fell, each one organize the
information, a lot of visual stimulate, like I am staring at the classroom. DO the things first, and
then organize the information.
Top-down Processing – using our existing cognitive structures (memories, thoughts) to
influence our processing of the environmental stimulus. (We use our memories and to think
about what’s going on) You organize the meaning before you stimulus.
The memories & thoughts help to influence the processing of the stimuli - helping to fill
in the blank information, or helping to quickly organize the existing stimuli

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Transduction – the conversion of one form of energy into another form of energy.
In the nervous system, transduction occurs when environmental energy is transformed into
electrical energy.
Sense organs convert energy from environmental events into neural activity.
Receptor Cells – specialized neurons that receive the incoming environmental stimulus and turn
this into an action potential (which is then carried toward the Central Nervous System).
Anatomical Coding – different types of environmental energy are coded by different neurons.
The brain interprets the location and type of sensory stimulus according to which incoming
nerve fibers are active.
Temporal Coding – another way that the nervous system represents information. Some features
are coded by the pattern of neural activity. The patterns of nervous activity, The time, we can
get extra.
Psychophysics – “the physics of the mind” studying the property of the environment and the
property of the nervous information.
Studying the relation between the physical characteristics of the environmental stimuli
(the distal stimulus) and the sensations they produce (the proximal stimulus).
Signal Detection Theory
The goal of psychophysics is to chart the relationships between a person’s responses and
various characteristics of the physical stimulus (the distal stimulus).
But these relationships are not always consistent, they can vary based on the situation and/or the
characteristics of the person.
(The relationship between environment and how encoded to nervous impusle) The nature of the
situation to the relation of stimulus.
Signal Detection Theory: the role: be able to distribute the signal and the noise.
Every stimulus event requires discrimination between the signal(stimulys that we try to detect)
and the noise
Signal – the stimulus (which may or may not be detected) It may not detected.
Noise – the background stimuli AND any random activity in our nervous system. The
background that we are trying to ignore.

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Signal Detection Theory
Threshold – the line between not perceiving and perceiving. Also talking about the change. The
previous and the occur.
This can refer to perceiving/not perceiving the change in the stimulus – the minimum
detectable difference between two stimuli – hence, the JND is also called the difference
Can also refer to the minimum value of a stimulus that can be detected (the absolute
threshold, the very first JND).
The J.N.D. (Absolute threshold)
The Just-Noticeable-Difference (JND) – the smallest change in the magnitude of a stimulus that
a person can detect (also called the “difference threshold”)
The JND is directly related to the magnitude of the stimulus.
Low magnitude – the size of the JND is small(Single salty, the size of the JND, it is
easier to detect)
High magnitude – the size of the JND is large(/JND, it is hard to high, like the volume
already high, if you want to tell the difference, you have to turn it really high)
Smaller change that we made, the detectible change that you can detect.
The JND & stimulus magnitudejust noticeable difference) environment stimulus, what ever the
stimulus change, can we notice the change in the environment. (different threshold) If you can detect
the difference, it is JND.
Example: A candle adds light to our environment.
A candle in a dark room adds a noticeable amount of light. Further, the difference
between one and two candles would be noticeably different.
A candle outside in the full light of the sun would not add a noticeable amount of light.
Further, we would not be able to notice the difference between one vs. two candles.
Orange juice example…
The JND & stimulus magnitude
The X-axis – measures of physical intensity (objective)
The Y-axis – the extent that the subjective perception is increasing (JND)
each one of the point is a JND, to be able detect one JND difference.
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