Psychophysics, in its most narrow and traditional aspect, has concentrated on the psychological problem of judged magnitudes or intensities, with a major focus on the relationships between perceived magnitude and stimulus dimensions (Uttal, 1978, p. 415). Its experimental paradigm has been the psychophysical experiment in which a single stimulus dimension (S) is manipulated and a single behavioural response dimension (R) measured (Uttal, 1998, p. 199). The trouble, however, with this narrow conception is that it mistakes procedure for problems and precision for goals. Psychophysics, in this narrow sense, becomes synonymous with a few methods for the determination of thresholds (Stevens, 1951, p. 31).
In its broader aspects, psychophysics can be seen as the science of the response of organisms to stimulating configurations. As such, it sees the responses as indicators of an attribute of the individual which vary with the stimulus and which are relatively invariant from person to person. As a science it tries to contribute to the 'invariance' of the human nature in relying on seven major categories of psycho-physical problems: (i) absolute thresholds (what are the stimulus values that mark the transition between response and no response?); (ii) differential thresholds (what is the resolving power of the organism, what is the smallest detectable change in a stimulus?); (iii) equality (what values of two different stimuli produce the same response or appear equal on the scale of some attribute?); (iv) order (what different stimuli produce a set of responses or psychological impression that can be set in serial order?); (v) equality of intervals (what stimuli produce a set of responses successively equidistant on the scale of some attribute?); (vi) equality of ratios (what stimuli produce a set of responses bearing constant ratio?); and (vii) stimulus rating (with what accuracy (validity) and precision (reliability) can a person estimate the 'physical' value of a stimulus?) (Stevens, 1951, p. 33).
It is easy to translate these psychophysical claims to the realm of music and to argue for some reliable correlation between acoustic signals and their perceptual processing. This correlation, further, embraces the conversion between the acoustic level of musical stimuli and the level of meaning, as well as the lawfulness or arbitrariness of this transformation.
The use of the term 'psychophysical' with respect to music, however, should be distinguished from its use in the broader field of psychophysics. Traditionally, the term refers to the relationship between a physical variable, like 'decibels, and a perceptual variable, like 'perceived loudness' (see Boring, 1942, for a historical perspective). The relationship may be a logarithmic function as described in Fechner's Law, or an exponential relationship as described in Stevens' Power Law (Stevens, 1975). In the literature of music psychology, however, the term psycho-physical has been used to refer to physical properties of music (e.g. tempo, pitch range, melodic complexity, rhythmic complexity) that may be defined and assessed independently of the musical conventions of any particular culture. It represents those qualities, which are not restricted to a particular musical style or culture, and which do not require detailed musical knowledge in order to interpret them or respond to them at an emotional level (Balkwill, 1997, p. 3-4). They mainly correspond to those characteristics of music to which basic auditory processes naturally respond (e.g. tempo/pulse speed). Tempo is an example: it can be measured in beats per minute (bpm), which is a quantifiable measure of occurrence over time, which could apply to any type of stimulus.
As such, there have been attempts to list up psychophysical elements of music. For the assessment of emotional content of Western music, e.g., the following elements have been summed up: tempo, modality, melodic contour, harmonic complexity, melodic complexity, rhythmic complexity, articulation, dynamics, consonance/dissonance, pitch register, and timbre (Holbrook and Anand, 1990; Gabrielsson and Juslin, 1996; Gerardi and Gerken, 1995; Kratus, 1993; Nielzén and Cesarec, 1982; Scherer and Oshinsky, 1977; see Balkwill, 1997, p. 13 for an overview).
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