Short Answer questions and answer for Textbook chapters 1,2,3,4,5,(7)
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Early Philosophy of Perception
Describe the idea of "The Allegory of the Cave" in Plato's Republic.
"The Allegory of The Cave" in Plato's Republic depicts our ordinary sense of reality as beings
like prisoners in a cave. The prisoners are tethered together since childhood, bound to face only
the wall in front of them, and all they are able to see are the shadows on the wall in front of
them. This is their reality, and this depiction is meant to show how much of our conception of
reality depends on what we can learn about the world through our senses.
Explain the mechanism of adaptation and provide an example.
Adaptation is a reduction in response caused by prior or continuing stimulation. For instance,
upon arrival at a loud stadium, one might notice the increase in noise level, but soon after, the
observer adapts to it, not noticing it anymore.
What are sensory transducers and how are they related to perception?
Sensory transducers are receptors that convert physical energy from the environment into
neural activity. According to Democritus, our perception is based on information passed through
these receptors from the outside world
Nativism and Empiricism
What is nativism?
Nativism is the idea that the mind produces ideas that are not derived from external sources.
Rather, all our abilities are innate and not learned through experience
Explain how Descartes is known as a dualist.
Descartes is known as a dualist because he believed in the idea that both mind and body exist.
In fact, he considered the mind to be quite separate from the body. For instance, the mind is
unextended (takes up no space), and has no substance. It is distinct from the body and survives
the death of the body, like a soul.
Describe empiricism and provide an example of one empiricist.
Empiricism is the idea that experience from the senses is the only source of knowledge. Hobbes
was an empiricist who believed that everything that could ever be known or even imagined had
to be learned through the senses.
Explain the notion of "tabula rasa."
"Tabula rasa," or "blank slate" is the famous concept formulated by John Locke, who proposed
that the newborn's mind is blank, waiting to be filled with information. This is done through
experience, which is the essence of empiricism.
The Dawn of Psychophysics
What is psychophysics?
Psychophysics is the science of defining quantitative relationships between physical and
psychological (subjective) events.
What is the "just noticeable difference" (JND) and why is it important in psychophysics?
The JND is the smallest detectable difference between two stimuli, or the minimum change in a
stimulus that can be correctly judged as different from a reference stimulus. It is also known as
the "difference threshold." It is a key tool for investigating psychophysiological phenomena.
Describe two psychophysical methods used to measure people's sensations.
1) The method of constant stimuli involves the presentation of many stimuli, ranging from rarely
to almost always perceivable. They are presented one at a time and participants respond to
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each presentation: "yes/no," "same/different," and so on. 2) The method of limits involves
presenting stimuli that vary incrementally in one dimension until the participant responds
What is the method of adjustment?
The method of adjustment is a psychophysical method, which uses the method of limits idea,
but in which the participant controls the change in the stimulus.
Explain Fechner's law.
Fechner's law is a principle describing the relationship between stimulus magnitude and
resulting sensation magnitude such that the magnitude of subjective sensation increases
proportionally to the logarithm of the stimulus intensity. As the stimulus grows larger, larger
changes are required for the changes to be detected by a perceiver.
Why is the JND important in psychophysics?
The JND, or "just noticeable difference" is the smallest detectable difference between two
stimuli, or the minimum change in a stimulus that can be correctly judged as different from a
reference stimulus. It is important in psychophysics because psychophysics involves measuring
people's perception, and the JND is an important landmark in understanding their perception.
Using this landmark experimenters are able to make conclusions about the way in which we
perceive stimuli. In fact, the JND is a constant fraction of the comparison stimulus (Weber's Law
What are the signal and noise in the signal detection theory?
The signal detection theory is a psychophysical theory that quantifies the response of an
observer to the presentation of a signal in the presence of noise. The signal is the target
stimulus and the noise is the interference that occurs, and is sometimes confused with the
What is magnitude estimation?
Magnitude estimation is a psychophysical method in which the participant assigns values
according to perceived magnitudes of stimuli
Biology of Perception
What is the central idea of Müller's doctrine of specific nerve energies?
The central idea of Müller's doctrine of specific nerve energies is that we are aware only of the
activity in our nerves, and we cannot be aware of the world itself. In addition, what is most
important is which nerves are stimulated, and not how they are stimulated.
What are cranial nerves?
Cranial nerves are twelve pairs of nerves that originate in the brain stem and reach the
periphery through openings in the skull. They are dedicated mainly to sensory and motor
What is Helmholtz's ophthalmoscope used for?
Helmholtz's ophthalmoscope is a device used to look directly at the retina, the sheet of blood
vessels, receptors, and neurons across the back of one's eye. It assists with the diagnosis of
eye problems, and allows the observer to see the only part of the central nervous system that is
visible from outside the skull.
Explain how neurons communicate with one another.
Neurons have axon terminals (presynaptic) as well as dendrites (postsynaptic). The axon
terminal of the presynaptic neuron binds to the dendrite of the postsynaptic neuron.
Neurotransmitters are now released by synaptic vesicles in the axon and fit into receptors on the
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dendrite on the other side of the synapse, thus communicating from the axon of the first neuron
to the dendrite of the second neuron.
What are neurotransmitters?
Neurotransmitters are chemical substances used in neuronal communication at synapses
When is an action potential created?
An action potential, or firing of a neuron is created when the membrane of the neuron permits
sodium ions to rush into the cell, thus increasing the voltage. Very quickly afterward, potassium
flows out of the cell, bringing the voltage back to resting voltage.
A Little Light Physics
Describe the two ways used to conceptualize light.
One way to conceptualize light is to think of it as a wave. Another way is to think of it as a
stream of photons, tiny particles, each consisting of one quantum of energy.
Describe the difference between light that is reflected and light that is transmitted.
Reflected light occurs when a ray of light strikes a light-colored surface and then bounces back
to its point of origin. Transmitted light occurs when light is neither reflected nor absorbed by a
surface. It occurs when the surface is transparent, such as in the case of a window. In this case,
light is passed through the surface.
Eyes That See Light
What is the purpose of the cornea?
The cornea is a transparent surface on the exterior of the eye. It protects the eye from the
outside world. Being transparent, it allows the light to be transmitted through it and into the eye.
What is the purpose of the retina?
The retina is a light-sensitive membrane in the back of the eye that contains rods and cones,
which receive an image from the lens and send it to the brain through the optic nerve.
How does the process of accommodation take place in the eye?
Accommodation takes place in the lens of the eye. The lens changes its refractive power by
changing its shape. This causes the eye to be able to focus on a given object
What is astigmatism and how can it be fixed?
Astigmatism is a visual defect caused by the unequal curving of one or more of the refractive
surfaces of the eye, usually the cornea. It can be fixed by wearing lens that have two focal
points (that provide different amounts of focusing power in the horizontal and vertical planes).
Why are photoreceptors important in the process of seeing?
Photoreceptors are the cells that make up the backmost layer of the retina. They are sensitive to
light, and as soon as they sense it, they can cause neurons in the intermediate layers to fire
action potentials. Photoreceptors are important in the process of seeing because by causing
neurons to react to light they help continue the process of seeing.
Retinal Information Processing
What are rods and cones?
Rods and cones are photoreceptors present in the retina. Rods are specialized for night vision,
while cones are specialized for daylight vision, fine visual acuity and color
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