Can man function effectively, let alone survive, in the exotic environments to which the astronaut will be exposed? The answers promise to be of scientific interest as well as practical consequence. Optimistic forecasts have been made of man's ability to perform efficiently in outer space for indefinitely long periods. These predictions have generally been based upon observations of human adaptability to the many and diverse circumstances found above, below, and on the surface of the earth. Some of the conditions to be encountered in space have been simulated by existing equipment on earth, and their consequences for human performance have been tested. Other conditions cannot be so directly tested, and informed speculation becomes necessary. For example, the effects of gravity have been reduced to zero for periods of less than 1 minute in aircraft flying Keplerian trajectories; subgravity states of longer duration have been achieved only in space vehicles. But even in the space flights of long duration astronauts have not yet experienced prolonged periods of free movement at zero gravity. For this condition, we make a less optimistic forecast, based upon recent analyses of sensorimotor function.Dr. Held is professor of experimental psychology in the psychology section of the Massachusetts Institute of Technology,

This study is concerned with relationships between descriptions of visual imagery produced by rhythmic photic stimulation and a number of personality tests. Individuals who manifested the ability to suspend their generalized reality‐orientation described more imagery; imagination and suggestibility also seemed to be important. Subjects' expectations about what they would see influenced their reports, although comprehension of the experimental design, fatigue and motivation were not relevant. The correlated personality variables indicate a close relationship with other types of visual imagery; the phenomenology fits a synthesized description of sensory deprivation, mescaline, and hypnagogic imagery.

Comparisons were made between the compensations produced by sagittal and by transverse arm motions under equivalent conditions of exposure and test. Effects of exposure with sagittal motion generalize more to transverse than vice versa. The differences may be related to the greater precision of body midline judgments with saggital motion.

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