Male, medical and graduate students were subjected to a non-discriminated avoidance regimen with shock-shock and response-shock intervals of 10 sec. Using a yoked-chair procedure it was found that acquisition of the button-pressing avoidance response was influenced by the social environment in which the conditioning occurred. There was a significantly greater number of "learners" among subjects conditioned individually than among those exposed to the conditioning procedures in the presence of a second person.

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Levels of serum androgens and sex hormone binding globulin (SHBG) were measured in 20 obese Pima Indian females aged 19-44 and compared with those of normal-weight Caucasians aged 20-46. The Pima exhibited significantly decreased SHBG compared to Caucasians, but a strong effect of age on androgen levels rendered mean comparisons useless. Androstenedione (A) and dehydroepiandrosterone-sulfate (DHEA-S) decreased significantly, and testosterone (T) declined slightly with age in the Pima, whereas these androgens showed no significant decreases in Caucasians for this age range. A possible relationship of androgens to the Pima female's propensity for android obesity as well as possible effects of obesity on SHBG, and aging is discussed.

Previous research with animals has shown that an avoidance response can be established and maintained without the use of an exteroceptive warning stimulus (Sidman, 1953a(Sidman, , 1953b. The procedure involves presentation of a brief electric shock at periodic intervals, the shock-shock (S-S) interval. The animal's leverpressing response delays the onset of shock by a second interval, the response-shock (R-S) interval, which may be less than, equal to, or greater than the interval between successive shocks. Such a technique results in stable rates of response which vary with the S-S and R-S intervals. The present study was undertaken to determine the feasibility of using this technique of freeoperant avoidance conditioning with human subjects. METHODThe subjects (Ss) were 36 male medical and graduate students between the ages of 21 and 29. These were volunteers who were told only that they would be paid three dollars to serve as research subjects for a period which might range from 10 minutes to 3 hours. When Ss arrived for the experiment, they were told that they would be taken to another room, that they would be seated in a chair, and that electrodes would be attached to their legs. They were instructed not to get up from or move the chair, nor touch the electrodes. They were also asked not to smoke or vocalize, and were told that the experimenter would be in the next room. At no time were Ss told anything of the nature of the experiment.Each S was then taken to a small room and seated in front of a table. A red button on a wooden board was fastened to the edge of the table, directly in front of S. EKG-type electrodes were affixed to the calf of S's left leg. Apparatus controlling the conditioning regimen was located in an adjoining room from which observations of S's behavior could be made via a one-way glass screen.The Ss were randomly assigned to one of three groups, each of which received an electric shock for 0.5 second at S-S intervals of either 5, 10, or 20 seconds. Electric current was set at that intensity which evoked an involuntary leg flexion. The Ss' most common response was that the shock was "unpleasant," "uncomfortable," or "bothersome." Only R-S intervals equal to the S-S intervals could be programmed, so that when S pressed the button the shock was delayed 'The authors are grateful for the assistance of Carol Klingberg and to G. L. Engel, F. Reichsman, and N. I. Harway for their critical review of the manuscript. Each conditioning period lasted 90 minutes unless S had removed the electrodes earlier.The arbitrarily chosen criterion for acquisition of the avoidance response varied with the S-S and R-S intervals. For S-S = R-S = 5 seconds, the criterion was a 5-minute period during which S made a minimum of 60 responses and received no more than 10 shocks. For S-S = R-S = 10 seconds, the requirement was a minimum of 30 responses and no more than 5 shocks; and for S-S = R-S = 20 seconds, a minimum of 15 responses and no more than 3 shocks was required during a 5-minute period. The point at which...