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Five pigeons were trained on a variety of concurrent interval schedules that arranged reinforcements at either fixed or variable times after the last reinforcement. Two measures were obtained: the number of responses on each schedule, and the time spent responding on each schedule. Ratios of response rates on the two schedules did not equal ratios of reinforcement rates when both schedules were variable nor when one was variable and the other fixed. Ratios of times spent responding approximately equalled ratios of reinforcement rates when both schedules were variable, but did not do so when one was fixed.

Newly hatched Khaki Campbell ducklings (Anas platyrhynchos domesticus) were exposed to a moving object that immediately suppressed distress vocalizations occurring in a novel environment. The static visual and auditory features of this object acquired the ability to suppress distress vocalizations after eight 20‐min sessions of exposure to the object in motion. The acquired suppressive properties of these features were found to persist throughout thirty 20‐min sessions given over 10 days. During these sessions, the ducklings were continually exposed to the static features in the absence of visual movement. In a second experiment, the ability of these features to serve as reinforcement for a pecking response was shown to persist for up to 56 hr. In one duckling, presentations of the static visual features did not maintain pecking behavior. However, it was shown that pecking responses could be re‐instated in this duckling by introducing novel stimuli to the environment.

Three groups of rats received either 8, 23, or 53 sessions of multiple variable‐interval variable‐interval baseline training before being shifted to a multiple extinction variable‐interval schedule. The rate of responding during the unaltered component was higher for the groups shifted to multiple extinction variable‐interval than for control groups remaining on multiple variable‐interval variable‐interval (positive contrast). Furthermore, when the multiple variable‐interval variable‐interval schedule was re‐instated, stable negative contrast was found in the groups that had received 23 or 53 baseline sessions, but not for the group that had received only eight sessions. Positive and negative contrast were also demonstrated in the eight and 23‐session groups when the multiple extinction variable‐interval and multiple variable‐interval variable‐interval schedules were re‐administered in further phases of the experiment. These results suggest that both positive and negative behavioral contrast can be obtained reliably in a species other than the pigeon.

Four Asian quail (Coturnix coturnix japonica) were exposed to concurrent‐chain schedules, the terminal links of which were either variable‐interval 30 sec and variable‐time 30 sec, or fixed‐interval 30 sec and fixed‐time 30 sec. Except for one bird that exhibited a preference for the variable‐interval schedule over the variable‐time schedule, no consistent preferences were demonstrated for response‐dependent or response‐independent schedules. However, response rates were three times greater on response‐dependent than on response‐independent schedules. The discrimination between terminal‐link schedules was rapidly recovered after the schedule positions were reversed. Casual observations revealed that the birds engaged in stereotypic circling and pecking while the response‐independent schedules were operative.

The use of primes, contingent attention, and training sessions to assess a child's engagement and skill in six large motor activities was examined using a combination reversal and multiple‐baseline design. Assessment was based on four levels: proximity to equipment, touching equipment, unskilled participation, and skilled participation. Before training, priming (suggestion to the child) was more effective than contingent attention for increasing the subject's engagement (but not skill) in five activities and for increasing skilled participation in one activity. Training of four activities in the natural environment effectively increased the subject's skill level in five activities. Thus, training appeared to generalize to one of these five activities in this setting and also to skillfully executed stair climbing in an adjoining setting. After training, primes and contingent attention were sufficient to maintain both the subject's skill level and engagement in all activities. Postchecks in the same setting the following semester with different teachers revealed only slight increases in participation, as compared to previous baselines, but all participation was at the skilled level. Social interaction, which was not experimentally manipulated, did not systematically vary in relation to changes in experimental conditions.

Brown's book is selectively reviewed with the aim of noting points of similarity between Brown's psycholinguistic analysis of language acquisition and a functional analysis of verbal behavior. Brown divides early language acquisition into five stages, based on mean length of utterance in samples of child speech. His book concentrates on Stage I, when mean length of utterance first rises above 1.0, indicating that children are beginning to speak in multi‐morphemic utterances, and Stage II, when mean length of utterance in morphemes is about 2.25. Multi‐morphemic utterances in Stage I consist mainly of ordered sequences of uninflected nouns and verbs, the order being that of the simple declarative sentence (agent‐action‐indirect object‐direct object‐locative). The review attempts a theoretical analysis of the functional stimulus control of Stage I syntactic order, concluding that the control must originate partly in relations among events in the environment and partly in covert autoclitic verbal behavior. Increases in mean length of utterance in Stage II are mainly due to the appearance of several “grammatical morphemes” such as the progressive ‐ing inflection on verbs and the plural ‐s inflection on nouns. The review attempts a behavioral paraphrase, again in terms of tacts and autoclitics, of Brown's psycholinguistic analysis of grammatical morphemes, concluding that Stage II displays the further development, building on Stage I, of the combined control of verbal behavior by relations in the environment and covert self‐generated verbal stimuli. Similarities between Brown's psycholinguistic analysis and a functional analysis of language acquisition suggest that the two viewpoints are converging on a common concern with the stimulus control of verbal behavior.

Punishment with aromatic ammonia was used to eliminate self‐injurious behavior of an autistic woman during experimental sessions. The effects were reversible but were limited to experimental sessions until staff used the ammonia on the ward at all times.

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Acquisition of discrete‐trial lever‐press avoidance learning was studied in three experiments. Experiment I compared a new training procedure, which produces rates of lever‐press avoidance learning comparable to those obtained in shuttle boxes, with a “conventional”, less efficient training procedure. A factorial design was used to compare continuous versus intermittent shock and a long‐variable versus a short‐fixed signal‐shock interval. Learning was best in the groups trained with the long and variable interval and poorest in those trained with the short and fixed interval. Type of shock had no effect. Experiment II separated the effects of duration from those of variability of the signal‐shock interval. Fixed and variable intervals of 10 and 60 sec were tested and duration was the only significant factor. Experiment III addressed the effect of the differential opportunity to avoid provided by long signal‐shock intervals by varying this interval from 10 to 60 sec in 10‐sec steps. Only the 10‐sec group showed slow acquisition relative to the others. Analysis of avoidance response latencies showed that the distributions for all groups were positively skewed and that skewness increased with increasing duration of the signal‐shock interval. At intervals longer than 20 sec, the animals made progressively less use of their increased opportunity to respond. The data do not support the opportunity‐to‐respond interpretation of the effects of duration of signal‐shock interval and suggest that some type of inhibitory process may block lever‐press avoidance learning at intervals as short as 10 sec. The significance of these findings for species‐specific defense reaction and preparedness theories was emphasized.