Studies from two different laboratories tested for equivalence classes in individuals with severe mental retardation and minimal verbal repertoires. In the first study, 3 individuals learned several matching-to-sample performances: matching picture comparison stimuli to dictated-word sample stimuli (AB), matching those same pictures to printed letter samples (CB), and also matching the pictures to nonrepresentative forms (DB). On subsequent tests, all individuals immediately displayed Emergent Relations AC, AD, BC, BD, CD, and DC, together constituting a positive demonstration of equivalence (as defined by Sidman). The second study obtained a positive equivalence test outcome in 1 of 2 individuals with similarly minimal verbal repertoires. Taken together, these studies call into question previous assertions that equivalence classes are demonstrable only in individuals with well-developed language repertoires.

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In the first of two experiments, periods of noise were terminated with unavoidable shock to 36 rats. The rats' continuously reinforced responding was later completely suppressed during the noise when it was introduced without shock. The rats were then assigned to nine experimental groups. Each group was exposed to different paced variable-interval schedules of reinforcement, which independently controlled response rate and reinforcement frequency. Periods of the noise were periodically superimposed on these schedules, and loss of response suppression was studied. Differences between the groups were assessed statistically. The second experiment used a steady-state design. Six rats were exposed to paced schedules which generated two alternating response rates but gave constant reinforcement frequencies, and six rats to schedules which maintained the same response rates throughout, but in which the reinforcement frequency was alternately high and low. Response suppression was studied during a pre-shock stimulus superimposed on each rat's two behavioral baselines. Both experiments suggest that (1) conditioned suppression is affected by rate of operant responding, high rates being most suppressed, and (2) the frequency of reinforcements obtained also has an effect, most suppression occurring when frequency is low.

(1971). Prenatal Psychological Stress and Offspring Behavior in Rats and Mice. DEVELOPMENTAL PSYCHO-BIOLOGY, 4(3) 193-248. The experimental literature on the behavioral sequelae of prenatal stress in rodents is reviewed, from which few conclusions can be drawn except that some change in activity-reactivity may be induced. Were more careful consideration given t o certain methodologic dimensions, greater clarity of empirical relations could be achieved. These dimensions are: (I) the sex, species, and strain of animal observed; ( 2 ) the specification of the prenatal manipulation; and (3) the precision and completeness of the behavioral description which is the dependent variable studied. Multiple descriptions, as in a test-battery approach, appear t o be inefficient and generally unwarranted. prenatal stress stressors methodology emotionality laboratory rat laboratory mouse

Two specialist community services for people with learning disabilities and challenging behaviour were evaluated over approximately 3 years. Intervention effectiveness was assessed with respect to changes in subjects' skills, challenging behaviours, mental health and quality of life, and to changes in staff morale. Subjects assessed as having challenging behaviour but not referred for specialist input were also studied. Comparison of changes in referred and non-referred samples over time showed minor differences only, indicating little intervention effect and demonstrating stability in the comparison sample. Analysis of the two services separately yielded different results. Positive client change was evident with respect to one service, whilst little change was noted with respect to the other. There was little evidence to suggest that either service had any effect on staff morale. Differences between the two services in terms of structure, staffing characteristics and operational policies are discussed as possible factors in the differential results obtained. A major issue raised by the study concerns the quality of settings from which the subjects were referred for specialist support. This is discussed as a factor which may limit the effectiveness of specialist input.