Chapter 1 Study Questions
Welcome to Our World
1. What is the difference between sensation and perception?
Answer: Sensation is the ability to detect a stimulus and, perhaps, to turn that detection into a private experience. Perception is the act of giving meaning to a detected sensation.
Thresholds and the Dawn of Psychophysics
2. What is the difference between dualism and materialism?
Answer: Dualism is the idea that the mind and body are separate, that the mind has a non-material existence independent of the material world of the body. Materialism is the idea that the only thing that exists in the universe is matter, and that both the mind and body are made of matter—the mind is what the brain does.
3. What is the “just noticeable difference” (JND)?
Answer: 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.
4. What is psychophysics?
Answer: Psychophysics is the science of defining quantitative relationships between physical and psychological (subjective) events.
5. Explain Weber’s law.
Answer: Weber’s law is the principle describing the relationship between stimulus and resulting sensation that says the just noticeable difference (JND) is a constant fraction of the comparison stimulus. In other words, the JND is proportional to the stimulus magnitude.
6. Explain Fechner’s law.
Answer: 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.
7. Describe the method of constant stimuli.
Answer: 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 each presentation: “yes/no,” “same/different,” and so on.
8. What is the method of limits?
Answer: The method of limits involves presenting stimuli that vary incrementally in one dimension until the participant responds differently.
9. What is the method of adjustment?
Answer: 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.
10. What is magnitude estimation?
Answer: Magnitude estimation is a psychophysical method in which the participant assigns values according to perceived magnitudes of stimuli.
11. What is Stevens’ power law?
Answer: It is a principle describing the relationship between stimulus and resulting sensation that says the magnitude of subjective sensation is proportional to the stimulus magnitude raised to an exponent. Exponent values less than one yield curves that get flatter as stimulus values increase, whereas exponent values more than one yield curves that continuously increase as stimulus values increase. An exponent value of one yields a straight line.
12. How does cross-modality matching work?
Answer: In cross-modality matching, the observer adjusts the intensity of one kind of stimulus until it matches the perceived intensity of another kind of stimulus. For instance, adjusting the brightness of a light to match the spiciness of some food.
13. What are the signal and noise in signal detection theory?
Answer: 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 signal.
14. What is the difference between sensitivity and criterion in signal detection theory?
Answer: Sensitivity is the ease with which an observer can distinguish a signal from noise, regardless of any bias they may have in responding. The criterion represents your willingness to say “yes” or “no” to whether you perceived a potential signal and thus is a measure of your bias in responding.
15. What can be inferred by doing a Fourier analysis?
Answer: A Fourier analysis is a mathematical theorem by which any signal can be divided into a set of sine waves. Combining these sine waves will reproduce the original signal. Fourier analysis can be performed on sound waves and on images.
16. Define spatial frequency.
Answer: Spatial frequency is the number of repetitions of a sine wave per unit area. In audition, it is the number of cycles per second; in vision, it is the number of cycles per degree.
Sensory Neuroscience and the Biology of Perception
17. What is the central idea of Müller’s doctrine of specific nerve energies?
Answer: 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.
18. What are cranial nerves?
Answer: 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 systems.
19. Explain how neurons communicate with one another.
Answer: Neurons have axon terminals (presynaptic) as well as dendrites (postsynaptic). The axon terminal of the presynaptic neuron releases neurotransmitters that bind to receptors on the dendrite of the postsynaptic neuron, thus communicating from the axon of the first neuron to the dendrite of the second neuron.
20. What are neurotransmitters?
Answer: Neurotransmitters are chemical substances used in neuronal communication at synapses.
21. When is an action potential created?
Answer: 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.
22. Which forms of non-invasive brain imaging have the highest temporal resolution?
Answer: Electroencephalography (EEG) and magnetoencephalography (MEG) both have very high temporal resolution but low spatial resolution. They are the best techniques for making fine observations of an observer’s neural responses to a stimulus over time.
23. Which forms of non-invasive brain imaging have the highest spatial resolution?
Answer: Computerized tomography (CT) and magnetic resonance imaging (MRI) both have extremely high spatial resolution. They are the best options for creating non-invasive structural images of the brain.
24. Which forms of non-invasive brain imaging are good for investigating how the brain functions?
Answer: Functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) are both capable of visualizing the brain’s metabolic activity over time. fMRI tracks the flow of oxygenated blood in the brain, while PET tracks the metabolism of safe radioactive isotopes.