Search

This paper reports two experiments. In Experiment 1, the effects of chlordiazepoxide alone and in combination with a series of putative antagonists at various sites on the GABA/benzodiazepine receptor complex on conditioned suppression of operant behavior in rats were assessed. Response rates during presentation of a stimulus associated with shock (CS responding) and when only positive reinforcement is effective (pre-CS responding) were analysed. Chlordiazepoxide (10 mg/kg) significantly increased CS responding. This effect was significantly antagonised by Ro15-1788 (10 mg/kg) and by picrotoxin (1.5 mg/kg), but not by bicuculline (1.5 mg/kg) or by delta-amino-n-valeric acid (10 or 20 mg/kg). Chlordiazepoxide also significantly, albeit more slightly, increased pre-CS responding and none of the other drugs tested significantly antagonised this action, though Ro15-1788 plus chlordiazepoxide resulted in pre-CS response rates not significantly different from either chlordiazepoxide alone or control. These interactions are discussed in the context of the proposed GABA/benzodiazepine receptor complex with the conclusion that drug effects at the benzodiazepine- and picrotoxin-sensitive channel sites have an important role in mediating anxiolytic action. However, behavioral evidence of an important role for GABAa or GABAb receptors remains very limited. The second experiment studied the intrinsic actions of bicuculline, picrotoxin, and Ro15-1788 on conditioned suppression. Responding during a conditioned stimulus associated with a mild (0.125 to 0.15 mA) electric shock (CS responding) and a control rate of responding (pre-CS responding) were recorded. Bicuculline (1.5 mg/kg) and Ro15-1788 (10 mg/kg) did not significantly affect either response rate.(ABSTRACT TRUNCATED AT 250 WORDS)

The N-methyl-d-aspartate receptor agonist d-cycloserine (DCS) facilitates extinction following Pavlovian fear conditioning or conditioned place preference in rats, but its effects on extinction following operant conditioning are not previously established. We studied the effects of DCS on operant extinction with mice, previously shown to be facilitated by GABAergic potentiators including chlordiazepoxide. Following training of lever pressing by C57Bl/6 male mice on a discrete-trial fixed-ratio food reinforcement schedule with six reinforcers per session, 48-trial extinction sessions were conducted at 3- (Experiment 1) or 4-day intervals (Experiment 2). Effects of DCS (15 or 30 mg/kg, i.p.) administered immediately after 48-trial extinction sessions were compared with those of saline injections. With 3-day intervals between extinction sessions, post-session administration of DCS facilitated extinction, and this effect was stronger with 4-day intervals between extinction sessions. Facilitation of extinction by post-session drug administration persisted over a number of extinction sessions. Operant extinction in mice can be facilitated by DCS, a glutamatergic agonist, as well as by GABAergic potentiators. The relationship between glutamatergic and GABAergic processes in operant extinction is yet to be established. These findings strengthen the basis for clinical uses of DCS.

To establish a valid animal model of the effects of olfactory stimuli on anxiety, a series of experiments was conducted using rats in an open-field test. Throughout, effects of lavender oil were compared with the effects of chlordiazepoxide (CDP), as a reference anxiolytic with well-known effects on open-field behaviour. Rats were exposed to lavender oil (0.1–1.0 ml) for 30 min (Experiment 1) or 1 h (Experiment 2) prior to open-field test and in the open field or injected with CDP (10 mg/kg i.p.). CDP had predicted effects on behaviour, and the higher doses of lavender oil had some effects on behaviour similar to those of CDP. In Experiment 3, various combinations of pre-exposure times and amounts of lavender oil were used. With sufficient exposure time and quantity of lavender the same effects were obtained as in Experiment 2. Experiment 4 demonstrated that these behavioural effects of lavender could be obtained following pre-exposure, even if no oil was present in the open-field test. In Experiments 2–4, lavender oil increased immobility. Together, these experiments suggest that lavender oil does have anxiolytic effects in the open field, but that a sedative effect can also occur at the highest doses.

Herbert Spencer's Principles of Psychology (1855, first edition) was regarded by his contemporaries, including William James and John Dewey, as a major contribution to what was then a very new discipline. In this book he first expounded his ideas about both evolution of species and how behavior of the individual organism adapts through interaction with the environment. His formulation of the principle that behavior changes in adaptation to the environment is closely related to the version of the law of effect propounded some years later by Thorndike. He can thus be seen as the first proponent of selectionism, a key tenet of behavior analysis. He also explicitly attacked the then prevailing view of free will as being incompatible with the biologically grounded view of psychological processes that he was advocating, and thus put forward ideas that were precursors of B. F. Skinner's in this important area of debate.

This paper provides analytical chemical information on a range of psycho-active drugs. This analytical chemical information on liquid chromatography-electrospray ionisation-mass spectrometry (HPLC-ESI-MS), ion trap mass spectrometry (ESI-MS `'), gas chromatography-flame ionisation detection (GLC-FID) and polarographic behaviour is then incorporated into a database which is of use in drug characterisation. Application is found in the determination of selected drug compounds in hair samples. (c) 2006 Elsevier B.V. All rights reserved.

Several recent studies have shown that reducing gamma-aminobutyric acid (GABA)-mediated neurotransmission retards extinction of aversive conditioning. However, relatively little is known about the effect of GABA on extinction of appetitively motivated tasks. We examined the effect of chlordiazepoxide (CDP), a classical benzodiazepine (BZ) and two novel subtype-selective BZs when administered to male C57Bl/6 mice during extinction following training on a discrete-trial fixed-ratio 5 (FR5) food reinforced lever-press procedure. Initially CDP had no effect, but after several extinction sessions CDP significantly facilitated extinction, i.e. slowed responding, compared with vehicle-treated mice. This effect was not due to drug accumulation because mice switched from vehicle treatment to CDP late in extinction showed facilitation immediately. Likewise, this effect could not be attributed to sedation because the dose of CDP used (15 mg/kg i.p.) did not suppress locomotor activity. The two novel subtype-selective BZ partial agonists, L-838417 and TP13, selectively facilitated extinction in similar fashion to CDP. The non-GABAergic anxiolytic buspirone was also tested and found to have similar effects when administered at a non-sedating dose. These studies demonstrate that GABA-mediated processes are important during extinction of an appetitively motivated task, but only after the animals have experienced several extinction sessions.

In Experiments 1 and 2, lever pressing by rats was reinforced on a cyclic ratio schedule of food reinforcement, comprising a repeated sequence of fixed-ratio component schedules. Reinforcement magnitude was varied, on occasional sessions in Experiment 1 and across blocks of sessions in Experiment 2, from one to two or three 45-mg food pellets. In the one-pellet condition, post-reinforcement pauses increased with component schedule value. At higher magnitudes, post-reinforcement pauses increased, and overall response rates declined. Response rate on component schedules was a decreasing linear function of the obtained rate of reinforcement in all conditions. Plotted against component schedule value, response rate increased exponentially to an asymptote that decreased when reinforcement magnitude increased. These findings are consistent with regulatory accounts of food reinforced behaviour. In Experiment 3, rats were trained under a cyclic ratio schedule comprising fixed-ratio components including higher values, and some inverted U-shaped response functions were obtained. Those rats that did not showthis relationship were trained on cyclic ratios with even higher values, and all showed inverted U-shaped response functions. This suggests that behaviour on cyclic ratio schedules can reflect activating of reinforcement as well as the satiating effects seen in Experiments 1 and 2.

The study examined the possibility that propranolol, buspirone, pCPA, and reserpine have antianxiety effects by comparing their effects with those of chlordiazepoxide on an open-field test of emotionality in rats. The effects of intraperitoneal injections of d,l, propranolol (5, 10, 20 mg/kg), buspirone (1.25, 2.5, 5 mg/kg), reserpine (0.5 mg/kg), parachlorophenylalanine (pCPA) (100 mg/kg), and chlordiazepoxide (CDP) (2.5, 5, 10 mg/kg) were compared with performance of rats under saline or water using an open-field test on 5 successive days. Significant effects were found on peripheral movements, rearing, grooming, immobility, and defecation. The patterns of effects of high doses of propranolol and buspirone resembled those of CDP, while pCPA had some of the effects of CDP, and reserpine produced few effects. With propranolol, buspirone, and CDP, there was evidence of dose sensitivity. The effects of repeated testing across 5 days were different from these of CDP or other drugs. The results are consistent with the hypothesis that the effects of propranolol and buspirone on open-field behavior are anxiolytic, and may be mediated by action on the same brain systems.

Recent studies have demonstrated that visual and verbal suppression tasks interfere with olfactory memory in a manner which is partially consistent with a dual coding interpretation. However, it has been suggested that total task complexity rather than modality specificity of the suppression tasks might account for the observed pattern of results. This study addressed the issue of whether or not the level of difficulty and complexity of suppression tasks could explain the apparent modality effects noted in earlier experiments. A total of 608 participants were each allocated to one of 19 experimental conditions involving interference tasks which varied suppression type (visual or verbal), nature of complexity (single, double or mixed) and level of difficulty (easy, optimal or difficult) and presented with 13 target odours. Either recognition of the odours or free recall of the odour names was tested on one occasion, either within 15 minutes of presentation or one week later. Both recognition and recall performance showed an overall effect for suppression nature, suppression level and time of testing with no effect for suppression type. The results lend only limited support to Paivio's (1986) dual coding theory, but have a number of characteristics which suggest that an adequate account of olfactory memory may be broadly similar to current theories of face and object recognition. All of these phenomena might be dealt with by an appropriately modified version of dual coding theory.

It has been claimed that olfactory memory is distinct from memory in other modalities. This study investigated the effectiveness of visual and verbal tasks in interfering with olfactory memory and included methodological changes from other recent studies. Subjects were allocated to one of four experimental conditions involving interference tasks [no interference task; visual task; verbal task; visual-plus-verbal task] and presented 15 target odours. Either recognition of the odours or free recall of the odour names was tested on one occasion, either within 15 minutes of presentation or one week later. Recognition and recall performance both showed effects of interference of visual and verbal tasks but there was no effect for time of testing. While the results may be accommodated within a dual coding framework, further work is indicated to resolve theoretical issues relating to task complexity.

The generic account of selection proposed by Hull et al. readily fits operant learning where, by comparison with natural selection, the process is well understood but little is known about the mechanism. Objections within psychology, that operant learning ignores internal processes, fail to recognise the general significance of behaviour-environment interactions. Variation within operant response classes requires further investigation.

Different sciences approach the brain-behaviour system at various levels, but often apparently share terminology. “Function” is used both ontogenetically and phylogenetically. Within the ontogeny it has various meanings; the one adopted by Arbib et al. is that of mainstream cognitive psychology. This usage is relatively imprecise, and the psychologists who are sceptical about the ability of cognitive psychology to predict behavioural outcomes may have the same reservations about Arbib et al.'s cognitive neuroscience.

Although conditioned suppression has face validity as a technique for assessing resistance to change of operant behaviour, it is not discussed by Nevin & Grace. However, application of their approach to the results of a conditioned suppression study that varied food deprivation and reinforcement magnitude (Leslie 1977) produces paradoxical results.

Certain drugs generally regarded as GABA agonists, such as valproate and combinations of muscimol and baclofen, have been reported to produce apparent anxiolytic effects in various animal behavioral tests. The present paper reports two experiments on the effects of these agents on conditioned suppression in rats. In the first study, muscimol (0, 1.25 micrograms/kg or 1 mg/kg), baclofen (0, 1 mg/kg) and combinations of these treatments failed to alleviate conditioned suppression. Experiment Two showed that valproate (200 mg/kg) did attenuate conditioned suppression, and that its effects were antagonised by picrotoxin (1.5 mg/kg), but not by bicuculline (1.5 mg/kg), Ro 15-1788 (10 mg/kg) or by delta-amino-n-valeric acid (10 mg/kg). The findings are discussed in the context of the proposed GABA/benzodiazepine receptor complex, with the conclusion that there is little evidence for a mediating role of GABAa or GABAb receptors in such drug actions, and that the site of valproate action is probably the chloride ion channel associated with the receptor complex.

Rose provides a coherent account of how a number of simplifying assumptions apparently come together to support neurogenetic determinism, or “ultra-Darwinism.” This view, he demonstrates, is deeply flawed. He proposes instead that we must take account of the interaction of processes that determine our developmental trajectory at every stage. Unfortunately, he associates this defensible position with the claim that this gives freedom of action to humans. The implications of this for the interpretation of his general thesis are discussed.

The effects of presenting a brief visual stimulus followed by response-independent delivery of food to rats were studied in four experiments. Both sign tracking, operation of a response key (Experiment 1) or a lever (Experiments 2, 3, and 4), and goal tracking, operation of a food tray flap, were obtained. Lower rates of both types of response occurred when the visual stimulus was unrelated to food delivery. Possible influences of similarity between the visual stimulus and events accompanying food delivery were investigated by varying the visual stimulus and tray light conditions. Such an influence was detected only in a control condition when the stimulus was uncorrelated with food delivery. Various omission contingencies produced marked reductions in the target behavior.

Three experiments describe the effects of manipulating the frequency of response-reinforcer contiguity in a recycling conjunctive schedule. The schedule arranged that a reinforcer was delivered after 30 s provided at least one response had occurred; otherwise the next cycle started immediately. In Experiment 1, this schedule produced the typical pause-respond-pause pattern, with most responses at mid-interval; and, when a limited number of contiguities between responses and food delivery were added, the pattern became more like the monotonic scallop seen on fixed-interval schedules. In Experiment 2, the schedule was initially presented with an additional contingency that allowed contiguity on every trial. Fixed-interval-like behavior occurred and tended to persist as contiguities were gradually eliminated. In Experiment 3, the recycling conjunctive schedule alternated with a condition in which a large number of contiguities occurred. The pause-respond-pause pattern and fixed-interval-like performance occurred with few or many contiguities, respectively. The results of all three experiments illustrate how contiguity interacts with a small number of other variables to determine performance on interval schedules and illuminate previous findings with fixed-interval and fixed-time schedules.

Rats were trained to make a two-response chain under stimulus control for continuous reinforcement with sucrose. When the second response was punished with increasing intensities of footshock, responses/opportunity declined for both responses, and their latencies increased. After punishment was discontinued, responding was re-established on continuous reinforcement and the probability of reinforcement was then systematically reduced. As probability of reinforcement reduced, the probability of the response that initiated the chain declined but the response that completed the chain was relatively unaffected. While punishment, but not reductions in the probability of reinforcement, disrupted the response chain, the results are not easily interpreted in terms of a two-process theory of punishment.

Rats trained to lever press for sucrose were exposed to variable-interval schedules in which (i) the probability of reinforcement in each unit of time was a constant, (ii) the probability was high in the first ten seconds after reinforcement and low thereafter, (iii) the probability was low for ten seconds and high thereafter, (iv) the probability increased with time since reinforcement, or (v) the probability was initially zero and then increased with time since reinforcement. All schedules generated similar overall reinforcement rates. A peak in local response rate occurred several seconds after reinforcement under those schedules where reinforcement rate at this time was moderate or high ([i], [ii], and [iv]). Later in the inter-reinforcement interval, local response rate was roughly constant under those schedules with a constant local reinforcement rate ([i], [ii], and [iii]), but increased steadily when local reinforcement rate increased with time since reinforcement ([iv] and [v]). Postreinforcement pauses occurred on all schedules, but were much longer when local reinforcement rate was very low in the ten seconds after reinforcement ([iii]). The interresponse time distribution was highly correlated with the distribution of reinforced interresponse times, and the distribution of postreinforcement pauses was highly correlated with the distribution of reinforced postreinforcement pauses on some schedules. However, there was no direct evidence that these correlations resulted from selective reinforcement of classes of interresponse times and pauses.

Rats were trained to run up and down an alleyway for sucrose reinforcement on a variable interval schedule. Differential aversive classical conditioning with auditory CSs was then conducted in a separate apparatus ("off the baseline") prior to those CSS being presented while the subjects were responding for sucrose in the alleyway. Once the effects of the CSs had extinguished, shock was reintroduced following one CS but not the other ("on the baseline" differential aversive classical conditioning). Both "off the baseline" and "on the baseline" conditioning resulted in conditioned suppression to the CS followed by shock, but little effect of the CS followed by no shock was found. In the "on the baseline" phase, total suppression of baseline responding occurred at moderate US intensities, and this appeared to result from the subject avoiding the location at which he was last shocked. At lower values, both baseline response rate and relative suppression ratio were functions of US intensity. The results are discussed in relation to the effects found in similar experiments using avoidance baselines. Estes and Skinner (1941) found that food reinforced 1everpressing was suppressed by a conditioned stimulus (CS) that was followed by an unconditioned stimulus (US) of an electric shock. Such conditioned suppression of operant behavior by a preaversive CS has also been found using avoidance baselines (Bryant, 1972). However, Rescorla and Solomon (1967) were able to find support for their motivational account of operant classical interactions from a number of studies carried out in the Pennsylvanian laboratories (e.g., Rescorla & Lolordo, 1965; Rescorla, 1967). In general, these in­ volved training dogs to jump over a hurdle on a Sidman

Rats' lever pressing produced sucrose reinforcers on a variable-interval schedule where, in different conditions, the duration of a stimulus presented immediately after reinforcement was either correlated or uncorrelated with the duration of the current interreinforcement interval. Under the baseline schedule, in which no stimulus was presented, the minimum interreinforcement interval was 8 s and the mean postreinforcement pause of each subject approximated this value. Response rates increased slowly over the first 10 to 15 s and then remained roughly constant throughout the remainder of the interval. In both the correlated and uncorrelated conditions, the added stimulus resulted in the postreinforcement pauses lengthening to values in excess of the duration of the preceding stimulus. This resulted in a poststimulus pause which was, in most cases, roughly constant irrespective of the duration of the preceding stimulus, or of the reinforcement contingencies prevailing immediately after stimulus offset. Local response-rate patterns in the uncorrelated conditions were similar to those obtained under the baseline schedule in which no stimulus was presented. However, in the correlated condition local response rates increased across the remainder of the interreinforcer interval. Further, the rate of acceleration was inversely related to the duration of the preceding stimulus. These results show that a correlation between stimulus duration and the ensuing time to reinforcement can control behavior—a type of temporal control not previously reported.

In Experiment I, the responding of rats lever pressing on a variable-interval schedule for sucrose solution was partially suppressed by a variable duration conditioned stimulus followed by shock. When food deprivation was increased, response rates during and before the conditioned stimulus increased monotonically. Varying the concentration of sucrose across blocks of sessions or from session to session in a semi-random sequence had little effect on response rates either before or during the conditioned stimulus. With a fixed sequence of increasing concentrations across a five-session block, increased concentration produced much more rapid increases in response rates before than during the conditioned stimulus. In Experiment II, rats were presented with the same sequence of increasing concentrations across a five-session block. When tested at 80% body weight, response rates increased rapidly as concentration increased, but at 100%, body-weight rates increased only slightly. The effect of a change in body weight in Experiment II thus mimicked the effect of the conditioned stimulus in the latter part of Experiment I. These findings support the view that the effect of a pre-aversive conditioned stimulus is similar to that of a change in food deprivation, but unlike that of a change in reinforcement magnitude.

This paper examines the changes in the clarity of images over time under conditions varying in resource demands. In the experiments, subjects listened to descriptions of arrays of objects and moved a lever according to their assessment of the clarity of their visual images of the whole array. The position of the lever was sampled every half second by computer. The rated clarity of visual image (Y) increased over time (X) and fitted well to the power function Y = aXb for arrays of one to five objects. The increases in set size produced increasing demands on the resources of the limited capacity visual imagery system leading to an exponential-like decline in the final rating values across set size. In the first two experiments, increasing presentation rate produced a differentiation in the slopes (a) of the power functions fitted to each set size, because visualization is more difficult at the faster rate. As it is relatively more difficult to visualize larger arrays at the faster rate, a relativity hypothesis suggests that visualizing smaller arrays is relatively easier in the fast condition, producing the differentiation in slopes. The last two experiments further confirmed the relativity hypothesis and correspondingly falsified an alternative hypothesis predicting that images decaying over time produced these findings; for instance, in the last experiment, the slope (a) and exponent (b) of the power function were higher under the slow presentation rate indicating that this condition was easier. This was further confirmed by verbal reports and by the final rating values. The image decay hypothesis predicted the contrary result as the possibility of image decay was reduced in the fast condition. These results also elucidate previous experiments that demonstrated an increase in visualization latencies as a function of set size. In such experiments latencies increase as a function of set size because the clarity of the image is slower to reach criterion as the number of objects to be visualized increases.

State notation is a method of representing the procedures used in psychological experimentation concisely and unambiguously. It has formed the basis of three highlevel computer programming languages (ACT, SKED and SCAT) which have been developed for on-line experimental control systems. These languages are extremely powerful tools for programming procedures involving digital inputs and outputs. The power of minicomputers enables time-sharing systems to be used to run a number of complex experiments simultaneously (typically between 10 and 16). All three languages were developed for the experimental analysis of behaviour, but have also been used in a wide range of studies of human experimental psychology and in studies involving concomitant measurement of behaviour and physiology. The languages and associated hardware are less well able to deal with studies involving either very high temporal resolution or large quantities of verbal or other symbolic material. However, because state notation languages embody a conceptual structure that closely resembles that of much psychological experimentation, they are particularly easy for psychologists to learn and use effectively. For this reason, and because of the laboriousness of developing new programs for special applications, it is most efficient to have a state notation language generally available and to resort to other approaches only when it becomes unduly cumbersome.

Twelve mother-child dyads were videotaped during fortnightly 30-minute play sessions in a playroom within the psychology laboratories. At the outset of the project the children were aged 9–29 months and they took part in the study for an average of 7.5 months. A comprehensive 42-category coding system was developed to transcribe potentially communicative behaviour. Changes in individual category usage over the age range were identified and subjected to further analysis to discern common patterns of mother-child interaction which coincided with changes in child category usage. Frequent paired behaviours were isolated using conditional probabilities within a transition matrix and used as a basis for a further transition matrix. This analysis was carried out cross-sectionally across mother-child pairs within consecutive two-month blocks from 9 to 36 months. Common patterns of interaction were identified as those used by most mother-child pairs within any two-month block. Certain patterns were found to be used across the entire age range, whilst others were used only at particular ages. The majority of the more stable patterns of interaction involved imitation by the mother or child, or both, and the child's non-verbal compliance with the mother's orders. Those interactions which showed change with age involved the child behaviours of looking, pointing, labelling, giving information, denying and affirming. Mothers' behaviours within these latter interactions included labelling, giving information, questioning, imitation with questioning, pointing and direct imitation. Interaction patterns are discussed with reference to the child's language acquisition and their usefulness as possible teaching strategies.

A procedure is described which disrupts response-reinforcer contiguity and response dependency and which demonstrates how the location of the response dependency in interval schedules can be regarded as a controlling variable in its own right. Rats' lever pressing produced sucrose on a recycling conjunctive fixed-time 30-second fixed-ratio 1 schedule of reinforcement. Reinforcement occurred only at the end of the fixed-time component on this schedule and only if a response had occurred during that component. This produced a pause-respond-pause pattern during the interreinforcer interval for all animals. When the location of the response dependency was then restricted to a 10-second period in the middle of the fixed-time component, the pattern was accentuated and response rates increased for all animals, while postreinforcement pauses decreased sharply for two animals. When responding was required in the first 10 seconds of the fixed-time component, responding peaked earlier in the interval for all animals. Response rates were slightly below those in the previous conditions, while postreinforcement pauses were between 2 and 6 seconds across animals.

Rats were trained to leverpress concurrently for 4% and 16% sucrose solution. This established asymmetric performance. The introduction of a CS paired with free food resulted in an increased preference for the greater reinforcement. This result is discussed in terms of the motivational consequences of Pavlovian conditioning procedures.

The Yule-Oseretsky test of motor performance was administered to 10 ‘undifferentiated’ mentally-retarded adults, 10 normal children and 10 normal adults. In accordance with Denny's (1964) 3-group design, the children were matched on mental age with the retardates, the normal adults were matched on chronological age with the retardates, and the children and normal adults were matched on intelligence quotient. The results showed that mental age predicted performance on both fine and gross motor tasks, with the children and retarded adults both obtaining similar relatively-low scores.

A series of doses (0.5 to 2.0 mg/kg) of d-amphetamine was administered to rats whose lever pressing was maintained by fixed-interval 30-s, 60-s, or 120-s schedules of reinforcement by sucrose delivery. Under both saline and d-amphetamine conditions, molecular features of responding were reliably described in terms of the distribution of postreinforcement pauses and local response rate following the onset of responding. Postreinforcement pause always varied from interval to interval but, on average, shortened under the drug. Local response rate (response rate exclusive of pause time) tended to decrease under the drug, and where acceleration occurred within runs of responses, it was reduced by the drug. All of these effects were dose-related. These findings suggest that fixed-interval behavior can be analyzed effectively at a molecular level, and that the effects of d-amphetamine are best described as disruption of temporal discrimination.

When a fixed-time schedule of shocks was presented to rats lever pressing for food on a random-interval schedule, a pattern of behavior developed with a high rate of pressing after shock declining to near zero before the next shock was delivered. Once this pattern had stabilized, one-quarter of the shocks were replaced with brief auditory stimuli (tones) in a random sequence. Tone maintained behavior similar to shock, although tone was never paired with shock. Both tone and shocks elicited responding when presented at various times as probe stimuli, and responding was usually totally suppressed if neither stimulus occurred at the beginning of the fixed-time interval. When other stimuli were paired with tone and shock, only those paired with tone gained discriminative control and elicited responding. These findings suggest that stimuli that signal a shock-free, or safe, period will maintain the pattern of behavior generated by shock on a fixed-time schedule. There is a parallel between this phenomenon and the control of behavior on second-order schedules of positive reinforcement with nonpaired brief stimuli.

The effects of major and minor tranquillizers on an animal analogue of anxiety, the conditioned emotional response (CER), are surveyed. The apparent inconsistencies in results can be traced to drug interactions with acute versus chronic regimens of administration, and to the occasional failure to employ sensitive, stable behavioural baselines. The CER is analyzed into its relevant behavioural components, and an interactive motivational model is used to rationalise the effects of drug treatments. Although the evidence still remains far too fragmentary to evaluate the validity of the CER as a prototype of anxiety, human or animal, the technique is likely to continue to find a useful role as one element in the behavioural profile of pharmacological agents.

Over the 30 years of conflict, Northern Ireland escaped the worst excess of illegal drug trafficking and usage. However, the recent 'peace dividend' has brought with it an unprecedented rise in the availability and use of illicit drugs. With this, new problems and pressures have been brought to bear on the health service. The literature would suggest that drug users are loathed and feared by health care staff. Staff will also admit to be lacking in the knowledge and skills necessary for the delivery of appropriate support and treatment for this client group. Further, the literature has little to offer on the experiences and aspirations of drug users in relation to their treatment and the staff who care for them. In order to understand the drug users' experiences of health care and health staff, focus group methodology was employed to obtain qualitative data. A total of 20 illicit drug users from across Northern Ireland took part. Supporting the literature, all had experienced 'care' that they felt was filled with judgement, hostility and loathing. They recognized clearly the challenge they pose to health care staff. These findings indicate that there is obvious dissonance between those tasked to care for drug users and drug users themselves, with little respect being shown on either side. Results suggest that action needs to be taken to address the deficits in the knowledge, skills and values of health care professionals in relation to illicit drug users. The findings will be of interest to service providers within and outside the United Kingdom.