Operator performance during Space Shuttle and International Space Station robotic arm training can differ dramatically among astronauts. The difficulty making appropriate camera selections and accurate use of hand controllers, two of the more important aspects for performance, may be rooted in a problem mentally relating the various reference frames used by the displays, hand controllers and robot arm. In this paper, we examine whether the origin of such individual differences can be found in certain components of spatial ability. We have developed a virtual reality simulation of the Space Station Robotic Workstation to investigate whether performance differences can be correlated with subjects' perspective-taking and mental rotation abilities. Spatial test scores were measured and correlated to their performance in a docking robotic task. The preliminary results show that both mental rotation strategies and perspective-taking strategies are used by the operator to move the robot arm around the workspace. Further studies must be performed to confirm such findings. If important correlations between performance and spatial abilities are found, astronaut training could be designed in order to fulfill each operator's needs, reducing both training time and cost.

An extension of the work initiated by Quine in reducing an arbitrary Boolean truth function to its minimal form is presented. Apart from the unique parts of the form, the entire class of nonunique forms is discussed. The portion of the truth table that is left uncovered by the unique parts of the solution is partitioned into topologically invariant components of which it is the direct sum. Each component may be covered independently of the others. The generation of the set of coverings of a component is developed around a central theorem: A union of cells, all basic to a particular vertex, contains no further cells basic to that vertex. A proof of the theorem is given. The components are components in the topological sense and are preserved under changes of representation. The discussion focuses on the general, unrefinable structure of a Boolean function, as opposed to practical means for calculating its minimal coverings.