Mach’s Early Career

After completing his doctorate on electrical discharge and induction in Vienna in 1860, Mach began his career with lectures on physics for medical students. His research traced physical phenomena between motion and the senses, and the mind and the senses, absorbing but also critiquing what Gustav Fechner called psychophysics (Blackmore 1972). Like Hermann von Helmholtz, Mach was one of many who moved between physiology, physics and psychology. Examining at the same time physical phenomena, the senses that perceived them, and aesthetics, they were

Mach’s illustration of the technique used to elicit the phenomena now known as Mach bands

Fig. 6.1 Mach’s illustration of the technique used to elicit the phenomena now known as Mach bands. When this strip is pasted on a cylinder and spun, bright and dark bands appear at a and p respectively (Mach 1886/1897, Fig. 27)

knitting together the subject matter of three laboratory sciences that were beginning to burgeon institutionally.

Several elements of Mach’s research in this period informed both his rather complex philosophical stance towards sensations as the basis of knowledge, and his later critiques of Newton. Firstly, Mach was intimately concerned with how the relative motion of a source and the observer affected perception of sound or light (Mach 1860, 1873a). It is notable that in these cases observed differences in perception could be resolved by a better understanding of the physical phenomena, as long as one recognised the critical role of relative motion. You do not need to know much about the ear or eye to understand the shift in tone or wavelength that results from the Doppler effect, for example. At this time Mach also pursued a psycho-physical parallelism and so expected to find that some effects that seemed largely psychological would actually be found to have a physical correlate. One is the very different perception we have of a chord change if we concentrate on the high or low note when the first chord is sounded, a phenomena called accommodation. As Alex Hui has shown, Mach thought that shifting attention in this way would lead to changes in the ear, making the physiology of the ear critical to understanding what we hear in the different instances. Yet nearly a decade’s research failed to disclose such a physiological basis. Hui argues that this led Mach to focus on the importance of distinctively historical explanations, coming to believe that significant features of our hearing had to be learned; they depended upon cultural development (Hui 2013, 89-121).

Other phenomena taught something very different. In 1865 Mach discovered what we now know as Mach bands. The set up is illustrated in Fig. 6.1. If the strip of paper illustrated is pasted on a cylinder and spun rapidly, the physical phenomena might lead you to expect that we would see a varying field of black and greys with two sharp changes. In addition, however, we see two bands, a bright line at a and a dark one at p (Mach 1886/1897, Fig. 27; Ratliff 1965). In this case Mach had disclosed an effect that was physiological rather than being either simply physical or dependent on psychological attention or cultural learning, and his explanation was both relational and evolutionary.

As Paul Pojman has shown, Mach thought perception resulted from the comparison of stimuli. Those near the mean of the surroundings become effaced, while those above or below are disproportionately brought into prominence as a result of the evolutionary significance of the ability to detect variation and change. If we did not perceive relations but differences in illumination, one and the same object perceived in the same surroundings under diverse light intensities would become unrecognizable. Thus, Pojman summarises, Mach argues we do not perceive the world directly, for that would amount to chaos: “Sensations by themselves can have no organic meaning, instead we have evolved senses that perceive contrasts of perception, relations of perception” (Pojman 2011b, 124).

There are two important orientations to recognize in this early work on motion and sensation, and the mind and the senses. Firstly, Mach encounters such diverse relationships between physiological, psychological and physical phenomena that he hesitates to explain one in terms of the other. Secondly, he regards relational perspectives as critical and often explores them through studies of motion. A further significant point emerges from a paper that Mach published on the development of conceptions of space in 1866. Here, building on Hering’s discussion of visual space, Mach distinguishes between physiological spaces determined by sensory perception, and geometrical spaces, which are metrical, depending on measure. And he identified a third form of space, physical, which depended on the forces of matter (Mach 1866). This kind of distinction between interrelated perspectives on phenomena was to be characteristic of Mach’s approach. Thus Mach’s later focus on sensation, relative motion and space has highly concrete but also complex and subtle grounds in his early studies of sense perception.

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