Validity and Reliability of Certain Measures of Psychological Stress
In this study the appropriateness of a previously reported stress-sensitive measure was determined for a field situation involving a stressor with high face-validity. METHOD Subjects.-Two hundred Army recruits ( 120 Ss in the experimental group and 80 Ss in the control group) participated as Ss. Procedwe.-The suessor was a three-rope toggle bridge 200 ft. long and 50 fc. above a rocky ravine, over which Ss, wearing headsets wich earphone and microphone, were run individually. They were stopped midway for a recorded test (administered over the headsets) of immediate backward digit memory span. Another administration of an equivalent form was given either just before starting or just after crossing the bridge. Half of the experimental Ss were tested in each sequence. The control Ss were tested on, and before or after crossing a short mock bridge, approximately 1 fc. off the ground. Half of the control Ss were tested in each sequence also. Care was taken to space the rwo control testings so that the time-lapse between the first and second testing was similar to that occurring in the experimental condition. Little attempt was made to control for fatigue. Of the experimental Ss on the long, high bridge, 40 had had prior experience (earlier the same day) on a similar bridge not quite so long or high. The remaining Ss in this group were given no prior experience with bridge crossing. To facilitate the mechanical administration by tape recording, the digitspan test procedure was modified according to one described by Myers, Burday, Forbes, and Arbit ( 1958). Each adminiscration of the digit-span test consisted of two presentations each of seven different item-lengths (from 2 to 8 digits) in random order. Ss were required to recall each item bacbwurd immediately upon hearing a particular item-length. The digit-span test was chosen as a measure of the stress effect on the basis