Sensation And Perception Flashcards
In 1984, Ernst Weber published a book called ________, which was an…
De Tactu, an investigation of muscle sense
Ernst Weber’s book introduced the notion of
Just noticeable difference (JND)
In the mid 18th century, which psychophysics researcher discovered the relationship between physical stimuli and psychological responses to stimuli?
Gustav Fechner
Gustav Fechner founded ____ ____, which was the mathematical expression of….
Weber’s law, Weber’s discovery about just noticeable differences
Sir Francis Galton was one of the first researchers interested in _____ ______
Individual differences
For six years, Galton maintained an ___ ___ in which he….
Anthropometric lab, measured the sensory abilities of nearly 10,000 people.
Who founded gestalt psychology?
Max Wertheimer (1880-1943) - beginning with a visual illusion referred to as the phi phenomenon
Briefly, Max Wertheimer’s studies led him to conclude that…
The experience of this visual illusion (phi phenomenon) has a wholeness about it that is different from the sum of its parts. He, like other Gestalt psychologists, believed that an analysis of experience into parts is not a valid way of studying our conscious experience.
Psychophysics is concerned with
Measuring relationship between physical stimuli and psychological responses to the stimuli.
One of the most important concepts to understand in sensory perception is the concept of
Threshold
What are the two main types of threshold
Absolute and difference
Absolute threshold is
The minimum of stimulus energy that is needed to activate the sensory system
The amount of stimulus an individual can perceive is known as the
Absolute threshold
Another word for threshold is
Limen - for instance, SUBliminal perception refers to perception of stimuli below a threshold - in this case, below the threshold of conscious awareness
Difference threshold
How different two stimuli (in magnitude) must be before they are perceived to be different.
What is an example of finding the difference threshold, and include the equation
Compare a standard stimulus to the comparison stimulus, which is different from the value of the standard stimulus. The subject’s task is to adjust the weight of the comparison stimulus’s weight until it matches that of the standard stimulus. After repeated trials, the differences between the weight of the standard stimulus and comparison stimulus are averaged - this value is the difference threshold.
Difference thresholds and just noticeable differences measure the same thing, but in different __
Units. So, if a difference threshold is is 2kgs, this is also equal to 1 just noticeable difference. 4kgs would equal 2 just noticeable differences
Sensation is
The activation of receptors in the various sensory organs
Sensory receptors
Specialized forms of neutrons - the cells that make up the nervous system. Instead of receiving neurotransmitters from other cells, these receptor cells are stimulated by different kinds of energy - for example, the receptors in the eyes are triggered by light, whereas vibrations trigger receptors in the ears.
Weber’s law states that
The change in stimulus intensity needed to produce a just noticeable difference divided by the stimulus intensity of the standard stimulus is a constant: ?I/I=K?
?I = change in intensity - so, 11 candles - 10 candles/ 10 candles = K (the constant, which is also known as Weber’s fraction or constant)
In Weber’s law, the __K (constant), the better the ___.
Smaller, sensitivity
Does Weber’s law for all data?
No. It does not fit data at very low and high intensities.
According to Weber’s law, what’s important in producing a just noticeable difference is..:
not the absolute difference, but the ratio of them
The amount of stimulus energy that needs to be added or subtracted from a stimulus for a person to say they notice a difference
Difference threshold
Fechner’s law
Expresses the relationship between the intensity of the sensation and the intensity of the stimulus
What is the purpose of Fechner’s law?
To relate the intensity of the stimulus to the intensity of the sensation
Fechner derived his law from Weber’s law and determined that
sensation increases more slowly as intensity increases
Steven’s power law
Also relates to the intensity of the stimulus and the intensity of the sensation
What are we really measuring when we measure thresholds in experiments?
We are really measuring what the person says they perceived that they sensed rather than what they actually sensed
Signal detection theory suggests that
other, non sensory factors influence what the subject says they sense.
What are the non sensory factors that can influence signal detection?
Experiences, expectations, motives, etc. For instance, a cautious person may want to be absolutely certain they heard a tone before responding “yes, I heard a tone”. On the other hand, another person might have only an inkling that they heard a tone before responding “yes”.
Response bias
The tendency of individuals to respond in a particular way due to nonsensory factors.
Unlike the earlier psychophysics, signal detection theory gives us a way to measure
both how well the subject can sense the stimulus (sensitivity) and response bias.
In a basic signal detection experiment, there are two experimenter controlled situations possible on a particular trial: either a stimulus is presented or it is not. Why are trials in which the stimulus is NOT presented called noise trials or catch trials?
Because even if a stimulus isn’t presented, your sensory systems are still excited by background noise, such as the random firings going on in the nervous system.
In signal detection lingo, the stimulus is called
A signal
In stimulus detection theory, each trial is either called a — or a —- trial
Noise or signal
What is the participant asked to indicate on each trial in signal detection theory?
Whether or not a signal was present
Describe the following in terms of signal detection theory: hit, miss, false alarm, correct rejection (false negative)
You should know this
Habituation
Tendency of brain to stop attending to constant, unchanging information
Sensory adaptation
Sensory receptor cells become less responsive to an unchanging stimulus. For example, when the smell or garbage in the house is strong when you initially come into the house, but gradually becomes less noticeable.
Which of your senses does not adapt to a constant stimulus at the level of receptor cells?
Hearing
If you stare at something long enough, why doesn’t it disappear?
Even though the sensory receptors in the back of the eyes would adapt to and become less responsive to a constant visual stimulus, the eyes are never that still. There’s a constant movement of the eyes, tiny vibrations called SACCADES that people don’t notice constantly. However, the eyes do show sensory adaptation, so if the eyes didn’t move (which isn’t the case), the image would disappear.
The first step in all sensory information processing is __. Each sensory system has these to…
Receptors, react to sensory information
The second step in sensory information processing is __, which is…
Transduction, the translation of physical energy into neural impulses or action potentials
Once transduction occurs, the electrochemical energy is….
Sent to various projection areas in the brain along various neural pathways and can be processed by the nervous system
The cornea is the …., which does what?
Clear, dome-like window in the front of your eye, which gathers and focuses the incoming light
The pupil, the hole in the ___, does what?
Iris, contracts in bright light and expands in dim light to let more light in.
The iris, the ___ part of the eye, has… and does…
Coloured, involuntary muscles and autonomic nerve fibres, which control the size of the pupil and therefore, the amount of light entering the eye.
The lens, which lies right behind the ___, does what
Iris, helps control the curvature of the light coming in and can focus near or distant objects on the retina
The retina is located where in the eye?
The back
The retina is like a ___ filled with ___ ___and ___ ___.
Screen, neural elements, blood vessels
The __ is the image detecting part of the eye
Retina
The duplicity or duplicity theory of vision states that
The retina contains two types of photoreceptors. The organization of the retinal cells makes light pass through intermediate sensory neurons before reaching and stimulating the photoreceptors.
There is a __ __ where the optic nerve leaves the __ and there are no ___ here.
Blind spot, eye, photoreceptors
Cones are used for what?
Colour vision and perceiving fine detail
Cones are most effective when? And what do they allow us to see?
In bright light, they allow us to see chromatic and achromatic colours
Rods function best in ___ ___ and allow perception of…
Reduced illumination, achromatic colours only
Rods have low sensitivity to __ and are not involved in __ ___
Detail, colour vision
At the periphery of the retina, there are only __
Rods
Are there more rods or cones in the eye?
Many more rods
The middle section of the eye, the ___, contains only ___
Fovea, cones
What happens as you move further away from the fovea?
The number of rods increases while the number of cones decreases
Because the further away you move from the fovea, the fewer cones there are, this means that visual __ is best in the ___, and the fovea is most sensitive in ___ ___ vision.
Acuity, fovea, normal daylight
The connection between the receptors (rods and cones) in the optic nerve is not __, there are several layers of ___ in between, called:
Direct, neurons, (1) horizontal, (2) amacrine, (3) bipolar cells and (4) ganglion cells
Rods and cones connect with __ cells, which connect with the ___ ___.
Bipolar, ganglion cells
Ganglion cells group together to form the
Optic nerve
Because there are many, many more receptors than ganglion cells, each ganglion cell has to….. this results in…
represent the combined activity of many rods and cones. This results in a loss of detail as information from the photoreceptors is combined.
The greater number of receptors that converge through the bipolar neurons into one ganglion cell the more…
difficult it becomes to make out the fine detail
On average, the number of cones converging onto individual ganglion cells is ___ than the number of rods converging onto individual ganglion cells. Therefore, cones have a…
smaller, greater sensitivity to fine detail than the rods do.
From the optic chiasm, the information goes to which places in the brain:
- Lateral geniculate nucleus of the thalamus
- The visual cortex in the occipital lobe
- The superior colliculus
- remember the visual system is SUPERIOR, and so it is the superior colliculus that is involved, not the inferior colliculus
Hubel and Weisel’s work on the __ ___ earned them a Nobel prize in 1981
Visual cortex
Hubel and Wiesel found a ___ basis for what?
Neural, feature detection theory
Feature detection theory suggests that
Certain cells in the cortex are maximally sensitive for certain features of stimuli.
Hubel and Wiesel distinguished 3 types of cells. Name and define.
Simple - the responses of simple cells give information about the orientation and boundaries of an object
complex - give more advanced info about orientation, such as movement
hyper complex - give info about more abstract concepts, such as object shape
Hubel and weisel’s work was considered an amazing breakthrough because…
The idea that single cells could give info about such specific features was an amazing breakthrough