This is an excerpt from Vision and Goal-Directed Movement by Digby Elliott & Michael Khan.
Almost 10 years before Paul Fitts published his landmark work formalizing the speed-accuracy trade-off for aiming movements, he was developing the genesis of this model with work targeted at the commendable goal of stopping airplanes from falling from the sky (Fitts & Jones, 1947; Fitts, Jones, & Milton, 1950). These studies into pilot error were some of the first to develop and apply theoretical models of motor control to the maximization of performance and the reduction of error in applied human-environment interactions. In this chapter, we explore how work spaces, as well as objects and displays within work spaces, can influence motor performance. We begin with an overview of applied motor behavior research, with an emphasis on human performance psychology, and examine how that research gave rise to the modern discipline of human factors. From there, we review topics pertaining to performance vis-à-vis human-environment interactions. Subtopics in this section include the role and function of the human sensory systems and the processes of perception and cognition. At the end of each section, we discuss how our understanding of these issues can either help or hinder our daily interactions with a working environment.
A Little History
Throughout history, humans have sought ways to make work easier, more cost and resource efficient, and safer. The term ergonomics (derived from the Greek “science of work”) has been used since the early 1940s to describe an eclectic body of research aimed at achieving these goals by exploring the psychology, physiology, anthropometry, and biomechanics of human interactions with work environments. At its most basic level, this research seeks to optimize the functioning of people with respect to their activities. Because the term ergonomics is necessarily broad, practical distinctions are now drawn between the physiological, anthropometric, and biomechanical contributions to this relationship (functional ergonomics) and those engendered by the sensory, perceptual, and cognitive limitations of the human performer or operator (cognitive ergonomics, or human factors). This chapter focuses on human factors and the perceptual-motor aspects of human-environment interactions.1
The scientific discipline of human factors is a neophyte compared with well-established research areas that are supported by several hundred years of published literature. Nevertheless, it has a long and distinguished academic lineage. Given the integrative nature of the field, it is impossible to determine precisely when human factors research began; however, a good starting point is Ernst Weber's and Gustav Fechner's pioneering work exploring human perceptual sensitivity (e.g., Fechner, 1860/1966; Weber, 1846/1978). This work provided clear evidence of human sensory and perceptual limitations and led to the development of the field of psycho-physics (the relationship between physical events and psychological events). Following were many landmark investigations that blazed a trail directly toward the point where human factors research stands today. A small sampling of these includes Donders' (1868/1969) application of chronometric subtractive logic procedures to mental processes (forming the central core of the information processing approach to human performance), Bryan and Harter's (1899) work with the learning of Morse code telegraphy (a seminal study for those interested in the broader field of motor skill acquisition), and Elton Mayo's (1933) 8 y series of studies on worker productivity at Western Electric's Hawthorne Illinois plant.2
Although the genesis of human factors research lies in studies conducted many years before the discipline started, the 20 or so years following the advent of World War II represented a true watershed for the discipline. This era brought together some of the most influential minds in human performance psychology (e.g., Frederic Bartlett, Margaret Vince, W.E. Hick, A.T. Welford, Donald Broadbent) in an attempt to answer specific questions arising from a general problem: how to better understand human operator capabilities and limitations in the face of the unprecedented technological improvements to machinery and work environments brought about by the war effort.
Studies from this time drew heavily on research dealing with issues such as depth perception, light and dark adaptation, gun sighting, target tracking, and the effects of fatigue on task performance. In England, much of this work was conducted at the Applied Psychology Research Unit at Cambridge University under the direction of Kenneth Craik (upon Craik's death in 1945, the directorship of the unit passed to Sir Fredrik Bartlett). In the United States, the driving force was provided by Alphonse Chapanis during his time (as the only psychologist) at the Aero Medical Laboratory (AML) at the Wright-Patterson Air Force Base in Ohio. In 1945, Paul Fitts joined Chapanis at AML, was appointed director of the laboratory's first psychology branch, and immediately set into motion a comprehensive, well-defined research program aimed at increasing aviation safety.
Fitts' work at AML was astonishing in terms of both volume and theoretical import (e.g., Fitts, 1947; Fitts & Crannell, 1950; Fitts & Jones, 1947; Fitts, Jones, & Milton, 1950). One excellent example of this research illustrated the new drive to feature the end user as a critical variable in the design of equipment (Fitts & Jones, 1947). Given numerous reports from pilots of problems experienced during instrument-only landings, Fitts and colleagues developed a link analysis procedure in which they recorded and analyzed the visual scan patterns of pilots across the cockpit instrument panel during runway approaches. Their idea was to identify which display instruments (e.g., air-speed indicator, directional gyroscope, altimeter) were viewed most frequently and in which order and then to compare this information to the spatial location of the instruments on the display panel.
The results showed that the greatest proportion of total gaze shifts occurred between two specific displays: the cross-pointer and the directional gyroscope. The problem was that a third instrument, the air-speed indicator, was situated directly between these two displays. Fitts and colleagues argued that this arrangement could be the reason for the reported pilot confusion (i.e., from what would now be referred to as a visual distractor) and that a simple repositioning of the display elements would solve the problem. This link analysis protocol, in which link values are established among elements within an environment and then used to best position those elements (i.e., such that the highest calculated link values are closest together), is still used today in the design of work environments ranging from data-entry systems to restaurants and bars.
As evidenced from these studies on scan patterns, Fitts was initially interested in how processing limitations in the human visual system had the capacity to constrain performance. In a series of studies run concomitantly with the link analysis work, Fitts investigated the accuracy of no-vision reaching movements to targets that were situated in various three-
dimensional locations in space. These were some of the first attempts by Fitts to explore goal-directed aiming movements and served as the forerunners for the seminal information transfer work that was to follow (and subsequently give rise to Fitts' law).