Minds and bodies need to be ready to engage the world. We need to be ready to act by moving muscles, and ready to perceive by looking and listening. We need to focus on things that are important and ignore things that are inconsequential. Moreover, we need to do all of these things in a way that is not simply reacting to existing situations; we need to anticipate and prepare for what might yet happen.
The human experience of music engages the basic physiological and psychological systems related to "preparedness" or "readiness." In this chapter, we introduce four components of "readiness," and demonstrate how these systems influence the experience and organization of music. Arousal is the term physiologists use to characterize the body's readiness for action. Attention is the term psychologists use to characterize the mind's readiness to perceive. Habituation is the first (of many) topics that relate to our ability to ignore things that are inconsequential, and to focus on things that are important. Finally, expectation pertains to how organisms anticipate what might happen in the near future.
As we will see, music influences the listener's state of arousal; music can be used like a sedative or tranquilizer or like a stimulant or pep-pill. We will see that some sounds are more likely to grab our attention than others, and that the principles of auditory attention explain many of the organizational differences between "background music" and foreground music. We will see that habituation plays the preeminent role in what musicians have commonly called form. Finally, we will see how musicians are able to play on listener's expectations in order to achieve specific emotional effects.
Our readiness to respond to the environment is not always constant. Changes in our level of mental engagement with the world are most obvious in the contrasting states of sleep and wakefulness. An individual's general metabolic readiness to act is referred to as arousal.
Arousal levels are reflected in a number of metabolic indices. Increased arousal is associated with increased heart rate, increased body temperature, increased rate of breathing, increased oxygen consumption, increased glucose uptake, faster reaction times, and many other physiological changes.
Increased arousal is associated with the release of epinephrine and norepinephrine (also known as adrenaline and noradrenaline). During high states of arousal, norepinephrine is delivered diffusely throughout the brain -- with particularly elevated amounts being delivered to the sensory regions on the brain's surface or cerebral cortex. Epinephrine (adrenaline) is released by the adrenal glands (which are located above the kidneys). Whereas norepinephrine raises the sensitivity of the sensory system in the brain, adrenaline acts in the body to raise the heart rate and tense muscles in preparation for physical exertion.
A good question to consider is why arousal levels change. Since a dangerous situation can theoretically arise at any moment, why isn't an organism always in the highest state of arousal? Of course high arousal levels are costly -- consuming large amounts of energy. For example, if a person were in a constant state of high arousal, they would need to consume 6 to 10 times their normal caloric intake. Changing arousal levels is nature's way of trying to tailor energy expenditures to a given situation. Many animals hibernate in the winter for the very good reason that there is insufficient food available to sustain a higher level of arousal. The danger of starvation outweighs the danger of being very slow to respond.
Changes in arousal are commonly divided into two basic types: tonic arousal and phasic arousal. Tonic arousal refers to relatively slow changes of base-level arousal. For example, the daily cycle of sleep and wakefulness represent changes of tonic arousal. Stimulants (such as caffeine) or depressants (such as alcohol) also produce notable changes in tonic arousal -- changes that may last several hours. The most important factor affecting tonic arousal is the diurnal cycle of wakefulness and sleep. Interestingly, the nature of the diurnal arousal cycle is known to relate to personality. Introverts tend to reach their point of greatest arousal or energy (so-called acrophase) earlier in the day than is the case for extroverts (Thayer, 1996; p.16).
A lesser factor influencing tonic arousal is age; peak arousal levels are higher for children and gradually decline with increasing years. Older people are much less likely to go berserk on a dance floor. A common mistake is to think that older people tend to be more reserved and less disposed to make fools of themselves. However, teenagers are much more afraid of social ostracism than the elderly. Whether one boogies or not depends primarily on arousal levels.
Phasic arousal is stimulus-related and more short-lived. For example, when a door is unexpectedly slammed shut by the wind, we experience a systemic increase in arousal due to the release of epinephrine and norepinephrine. Depending on the stimulus, changes in phasic arousal may last from a dozen or so seconds up to several minutes. Virtually every type of sound is able to influence phasic arousal, including environmental sounds, human-generated sounds (such as speech), and music. In general, arousing sounds are those sounds that imply either threat or opportunity. Typically, arousing sounds display one or more of the following properties: (1) loud sounds, (2) physically close sounds, (3) approaching sounds, (4) unexpected sounds, (5) sounds that have a learned association with danger, (6) sounds that have a learned association with opportunity, (7) sounds that are intended for us or addressed to us, and (8) sounds that indicate a high level of emotionality. It is worth discussing these eight different circumstances in further detail.
(1) Arousal levels generally increase in proportion to the loudness of the stimulus. There are two reasons why arousal and loudness are linked. In the first instance, louder sounds typically result from events involving larger energy expenditures or larger physical forces. Consequently loud sounds are more likely to accompany circumstances that pose a potential threat or danger. In the second instance, loud sounds cause masking -- where one sound can partially or completely obscure the presence of another sound. This means that loud sounds reduce our capacity to detect other sounds in the environment -- a potentially threatening situation. (2) Increased physical proximity to a sound source increases its importance to us. For example, the presence of a bee meandering through a flower bed may be of little concern, unless the bee happens to come very close to us. (3) Although human sound localization skills are somewhat crude compared with other mammals, we retain considerable sensitivity to sounds that are approaching us in space. Especially when the speed of approach is rapid, increases of phasic arousal are more marked. As we will see, musical crescendos are especially arousing -- principally because crescendos activate mechanisms for detecting approach. (4) Few sound stimuli have as marked an effect on arousal as `sonic surprises.' Children all over the world continue to delight in sneaking up behind their peers and scaring them with an unexpected "boo." (5) It is possible that some dangerous sounds -- perhaps the bark of a dog -- may be innate to humans, but most dangerous sounds are simply learned through experience (or training). To a security guard, the quiet sound of a pistol being cocked is a hair-raising sign of danger. (6) Conversely, some sounds are learned to be associated with an opportunity. A pet can be aroused from a light sleep merely by the sound of a refrigerator door being opened. (7) Some sounds are messages that are intended for us personally. The sound of one's name is certain to raise phasic arousal levels. Knowledgeable sales staff at car dealerships know that calling the customer by name will indirectly generate excitement. (8) Some sounds are indicative of a high degree emotionality. Most emotion-laden sounds are human vocalizations -- such as weeping, moaning, shouting, trembling voice, etc. However, emotional content may be evident in non-vocal sounds as well -- such as slamming doors, fast footsteps, tearing of paper, squealing tires, finger tapping, etc.
Although not as numerous, some sounds will tend to reduce arousal levels. In general, arousal is reduced when the sound indicates security or boredom. Of course silence is one of the best sounds for reducing arousal. Repeated low-level sounds (such as the slow ticking of a grandfather clock) will also tend to induce a low level of arousal. In both cases, low levels of stimulation mean that there is little in the environment that demands our attention. (Sleep is often not far away in such circumstances.) Sounds associated with security -- such as cooing sounds, relaxed whispers, calming or reassuring vocalizations, or the sound of someone yawning -- are also apt to reduce arousal levels.
In general, those sounds that most influence phasic arousal are human-generated sounds -- especially vocal sounds. An extreme example is evident in the case of a human scream -- which naturally will raise arousal levels in nearby listeners! Speech sounds that manifest high levels of emotionality such as joy, elation, anger, nervousness, grief, fear, or panic, are also apt to evoke increased arousal in a person who listens to these sounds.
An important fact about human-generated sounds is that they tend to evoke arousal levels in listeners that mimic the arousal level of the person producing the sound. An aroused speaking voice will evoke an aroused audience; a sleepy-sounding voice will put an audience to sleep. In effect, the sounds we make tend to influence other people in ways that make our arousal levels similar.
In the case of music, both tonic and phasic effects can be observed. Playing several pieces of stimulative music can raise arousal levels for an hour or more following the musical exposure; in addition, playing several sedate pieces can lower arousal levels. Audiences applaud less loudly after hearing sedate music than stimulative music. Similarly, listeners tend to sit with a more erect posture when listening to stimulative music (Gaston, 1968).
Arousal is increased via loud, energetic sounds. Sounds that are quiet and expected have a tendency to decrease phasic arousal. The degree of beat-accenting and the overall tempo also affect arousal. Long periods of arousal will lead to fatigue, and over arousal contributes to stress.
While music has the capacity to change arousal levels, our experience of music is also influenced by our pre-existing tonic arousal level. That is, our listening experience is affected by our initial arousal state. An extreme example is evident when we are asleep. Most people have little tolerance for music while sleeping, especially when the music has a high level of stimulation. Conversely, when in a highly aroused state, most listeners find sedate music to be uninteresting or inappropriate. When engaged in aerobic exercise, for example, listeners show a strong aversion against sedate music -- even if the tempo of the music matches the pace of the workout. With increasing age, people often show an increasing preference for sedate music. In general, listeners show a preference for music that matches their current arousal state. We can refer to this phenomenon as arousal compatibility preference.
In summary, one of the most basic metabolic effects linked to music is the level of evoked arousal. These changes may be short-lived (phasic arousal) or somewhat longer (tonic arousal). Arousal is influenced by overall loudness, by tempo, and by the degree of beat-accenting. Arousal is also influenced by the presence of emotion-laden lyrics and by tone-colors suggestive of high emotionality (e.g. anger). Our pre-existing arousal levels also influence how receptive we are to particular pieces of music. We tend to prefer music that matches our existing arousal level (arousal compatibility preference).
As a postscript, we might note that music is occasionally reported to occur while dreaming. These occurrences are of interest for at least four reasons: (1) It shows that musical experience requires neither sound stimuli nor conscious awareness/imagination. (2) It shows that music can be experienced even at very low levels of human arousal. (Only comas exhibit lower arousal levels.) (3) The music experienced while dreaming can exhibit a high stimulative level, yet the dreamer's body remains in a low state of arousal.
(4) Dreams often involve vivid emotional states. However, the emotions evoked while dreaming are known to be very restricted. So-called primary emotions (such as fear and anxiety) are common in dreams, but secondary emotions (such as shame or guilt) are rare.
Arousal is an important part of musical experience. Arousal interacts with a number of other phenomena, including attention and emotion. However, before we continue our discussion, we need to take a brief detour to learn about some pertinent physiological aspects of hearing. A particularly useful part of the puzzle is the so-called auditory evoked potential.
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