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Sixteen pigeons were trained to peck a key using a response‐independent (auto‐shaping) procedure of food presentation. The 4‐sec grain presentations were independent of responding but a keylight stimulus preceded each, with a 4‐min interval between the grain presentation and the next stimulus. Subjects were divided into four groups, with two durations of the keylight (30 or 120 sec) and either one or four successive colors on the response key preceding food delivery. In Phase 2, the birds were continued with the same keylight duration but were presented the alternative number of key colors. All pigeons pecked the key during the stimulus. Birds in the two groups with the 30‐sec stimulus duration began to respond significantly sooner than birds with the 120‐sec duration. There were no significant differences in rate of pecking between groups by the last five days of Phase 1. In Phase 1, the pigeons exposed to the four stimulus components showed an increase in rate of pecking over the four components as grain presentation approached. The pigeons with one stimulus component did not exhibit this regularity. Analogous conditions in Phase 2 had similar results except for one group. The implications of the occurrence of key pecking due to response‐independent food delivery for multiple and chained schedules were pointed out.

Rats detected the luminance difference of standard and comparison stimuli in a go/no‐go procedure. A key press was reinforced by brain stimulation only when the key's luminance was 10.53 ft‐L (36.01 cd/m2), and key presses to dimmer comparison values produced a 5‐sec timeout. These asymmetrical reinforcement contingencies maximized the bias toward hits and false alarms (“yes” reports), and thus the number of latencies available for analysis. False alarm latencies exceeded hit latencies, with the magnitude of differentiation proportional to luminance difference, demonstrating stimulus control on the very occasions that errors (key presses to comparison luminances) were emitted. Overall latencies decreased when the standard‐comparison luminance difference was made smaller, suggesting a reduction in observing time when the stimuli became indiscriminable.

In Experiment I, a 3‐min tone that preceded a free pellet of food suppressed variable‐interval performances maintained by the same type of pellets, but failed to elicit conditioned changes in the heart rates and blood pressures of two rhesus monkeys. Initially severe, the prereward suppression became temporally discriminated to progressively later portions of the tone, and was maintained at an attenuated level for over four months. The suppression was apparently not caused by interfering autonomic respondents, nor was it superstitiously conditioned, since 21 of the initial 25 tone‐food pairings took place outside of baseline sessions. In Experiment II, a 1‐min light, paired with four free pellets of food, suppressed the variable‐interval responding of a second pair of similarly trained monkeys. An interresponse‐time analysis showed that in one subject, mild prereward suppression of responding developed through two stages. On early trials, response rate slowed by 10% throughout the prefood interval. On later trials, the animal suppressed by pausing for a like portion of the interval, most often near the end, but otherwise responded normally during the prefood signal.

Resistance to extinction and generalization gradients were studied following training with a long‐adjusting‐interval schedule. One large reinforcer occurred at the end of each daily training session. Sessions varied in length from 20 sec to 42.66 min, but were usually the latter. Repeated generalization tests were subsequently conducted for these subjects and subjects trained with a more conventional short‐random‐interval schedule. The long‐adjusting‐interval schedule produced generalization gradients that were not qualitatively different from those produced by the conventional procedure. However, the advantages of the long‐adjusting‐interval schedule are: (1) greater resistance to extinction both within and across generalization tests and (2) more stable gradient slopes within and across tests.

Three pigeons were exposed to a series of procedures in which periods of response‐independent food presentation, on a variable‐time schedule, alternated with periods in which food was never presented. The stimuli that signalled periods of food availability or nonavailability varied from one procedure to the next, and were sometimes key colors, sometimes tones, and sometimes compounds of both. Key pecking was initiated and maintained when key color was a signal for food; key pecking was not initiated when a tone was the signal for food. However, control of key pecking that was already established could be transferred from key color to tone, and subsequently, initiated by the tone. It is suggested that for pigeons, pre‐experimental relationships exist among food, visual stimuli, and pecking, and that a similar relationship, which includes auditory stimuli, must be induced in the laboratory.

Reliability of observational data was measured simultaneously by two assessors under two experimental conditions. During overt assessment, observers were told that reliability would be measured by one of the two assessors, thus permitting computation of reliability with an identified and an unidentified assessor. During covert assessment, observers were not informed of the reliability measured. Throughout the study, each of the assessors employed a unique version of a standard observational code. In the overt assessment condition, reliability of observers with the identified assessor was consistently higher than reliability with the unidentified assessor, indicating that observers modified their observational criteria to approximate those of the identified assessor. In the covert assessment condition, reliability with the two assessors was substantially lower than during overt assessment. Further, observers consistently recorded lower frequencies of disruptive behavior than the two assessors during covert assessment.

The large number of nonexperimental manuscripts submitted to JABA and the lack of well‐defined criteria for evaluating them, has necessitated formulation of a separate editorial policy (see policy statement on page 404 of this issue). The manuscript by Alan E. Kazdin was submitted before the policy concerning nonexperimental manuscripts went into effect and was reviewed by three established researchers who have made substantial methodological contributions to the field (Montrose M. Wolf, Murray Sidman, and L. Keith Miller were Reviewers A, B, and C, respectively). On the basis of the reviewers' comments, it was decided to publish the manuscript with only minor changes. However, because of the fundamental importance of many of the issues discussed in Kazdin's paper and because of the lack of clear agreement on some of these issues, as exemplified in the reviewers' comments, these comments are presented below.