Violations of equifinality have been reported in a number of studies and are sometimes cited as evidence that refutes the equilibrium point hypothesis. Probably the most famous experiment was that of James Lackner and Paul DiZio. This involved performing movements performed by subjects seated in a rotary centrifuge (described in Section 4.5). The subject`s body was aligned with the axis of rotation and he or she performed gripping movements to illuminate targets in otherwise complete darkness. When the centrifuge was stationary, the trajectories were almost straight and quite precise. Then the centrifuge was accelerated very slowly, so that the subject did not notice the rotation. When the subject performed rotating experiments, the orbit moved away from the straight line under the action of the Coriolis force (Figure 11.25). It then showed a return to the initial trajectory, but the return was incomplete, and there was a residual error: a violation of equifinality. A system characterized by equifinality may be based on several development mechanisms, each activated by different conditions, but constrained in some way to achieve the same final product. The analogy here refers to several different machines, each of which only works when activated by a certain type of input (for example, a chicken, pig, cow or turkey). Despite the different processes that characterize the dismemberment operations of each machine, the machines produce the same sausage product. At first glance, it may seem unlikely that a multitude of development mechanisms would be forced to achieve exactly the same result.
However, it is relatively easy to imagine that the function performed by the mechanisms – a function that would be shared by all evolutionary trajectories – could have been sufficient to compel each of the mechanisms over time to produce the same product. Communication with other people via symbols could be a limiting function enough to lead to multiple mechanisms, each of which creates a language-like structure. In business, equivalence means that companies can gain similar competitive advantages based on substantially different skills. Part of what makes psychology methods useful in design is that the goals of a psychologist and a human-centered designer overlap a lot. A common overarching goal is that both aim to model and predict human behavior. Open systems theory would call this relationship equifinal. The words equifinality, multipurpose, unifinality and counter-finality are used to explain the relationships or connections between things. They are used in a variety of different studies, including psychology, economics, archaeology, and geomorphology, but are not explicitly used in the field of design. This article aims to provide an overview of these words, as well as examples of how they can expand designers` vocabulary and be identified and used in existing systems, from mid-end chains to conceptual models. The term equifinality refers to a particular characteristic of random movements, namely their ability to accurately reach targets under conditions where an unexpected transient external disturbance causes the moving system to deviate from its trajectory. A number of recent studies have reported violations of equifinality under conditions where subjects moved in a destabilizing force field. In a number of studies (Lackner and DiZio, 1994), subjects sat in the middle of a large centrifuge that accelerated very slowly, so subjects were not aware of rotation.
The gripping movements of the arms were performed without turning the centrifuge and then performed in total darkness towards an easy target. Without rotation, the trajectories were almost straight. During rotation, the Coriolis force acted on the hand during its movement. If the hand moves in a plane orthogonally to the axis of rotation of space, Coriolis force, FCOR = 2mωV, where ω is the angular velocity of the rotation of space, V is the speed of the hand and m is the mass. As a result, the trajectories were curved, strongly deviated from the straight, and then compensated for lateral deviation during the second half of the trajectory, but this compensation was only partial and the hand landed from the target (Figure 12.15). Since the Coriolis force acts only during motion, but not in the last steady state, residual errors in the final position were called equifinality violations.
