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Different groups of ducklings reared under sodium monochromatic light (589 nanometers) and under white light were trained to discriminate between the stimulus correlated with reinforcement (589 nanometers), and the stimulus correlated with extinction, whose value was either 570 or 610 nanometers. The peaks of subsequently obtained gradients of wavelength generalization of both groups were displaced away from the stimulus correlated with extinction. The peaks of the groups trained not to respond to 570 nanometers were located at 600 nanometers. The peaks of the groups trained not to respond to 610 nanometers were located at 580 nanometers. These results (in agreement with earlier data of Rudolph and Honig, 1972) suggest that ducklings have an innate basis for ordering stimuli of different wavelengths along the hue dimension.

Following a study of socially withdrawn children, it was noted that checks of experimenter calculations indicated discrepancies. The present study investigated the magnitude and direction of experimenter errors in data computations. Two full‐time research assistants, who served as experimenters, processed the behavioral observation data. These experimenters were referred to as the subjects in this study. Standard data values, against which the subjects' computations were compared, were established by two other research assistants and a computer staff. The results indicated that experimenters' original data values disagreed with the standard data values. The daily errors showed considerable variability for both experimenters. The specific factors accounting for this variability could not be identified, although frequency of experimenter responses required to obtain rate and duration data, time spent calculating, and complexity of task were suggested as possible contributing variables. While disagreements occurred across all experimental days, the magnitude of differences was generally small. An examination of direction of differences in both experimenters' data showed no systematic trends in favor of the experimental hypothesis. Rather, there appeared to be a trend in the other direction. This study suggests that the same research decisions would have been made during the original investigation using either set of data.

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Lever pressing by rhesus monkeys was maintained by morphine injections during four equally spaced sessions each day. During other periods, lever pressing was maintained by timeout from a continuous naloxone infusion (escape), or by timeout from a stimulus that preceded naloxone injections, or termination of the injections (avoidance‐escape). As naloxone dose increased in the escape procedure, response rate increased to a maximum and then decreased. In the avoidance‐escape procedure, response rate generally increased as naloxone dose increased, but the changes in rate were small compared to the escape procedure. Substitution of saline for naloxone in the escape procedure led to very low response rates within three sessions. In the avoidance‐escape procedure, rate decrements produced by saline substitution appeared to be related to the behavioral history of the monkey. Previous escape experience led to more rapid decreases in responding when saline was introduced, whereas responding was maintained for 15 sessions in a monkey without prior escape conditioning. Morphine pretreatment produced comparable, dose‐dependent decreases in response rates in both procedures. The rate‐decreasing effects of morphine were exacerbated when no naloxone was delivered in the escape procedure.