Four experiments explored the factors controlling human responding on random interval (RI) schedules of reinforcement. All experiments identified 2 types of responding: "bout-initiation" and "within-bout" responding. Responding on RI schedules was related to the interval value rates, being higher on an RI-30s than on an RI-60s or RI-120s schedule, which impacted bout-initiation responding to the greater degree (Experiments 1 and 3). Experiment 2 found similar overall response rates on random ratio (RR) and random interval with a linear feedback loop (RI+) schedules, with both higher than on an RI schedule. Bout-initiation rates were similar across all schedules, but within-bout responding differed. Experiments 3 and 4 examined the impact of a response cost and noted greater bout-initiation responding but not greater within-bout rates with low costs. Overall, these experiments suggest that bout-initiation responding may be subject to control by factors that increase the strength of conditioning to the context, whereas within-bout responding is less sensitive to these influences. (PsycINFO Database Record

Avoidance of threatening or unpleasant events is usually an adaptive behavioural strategy. Sometimes, however, avoidance can become chronic and lead to impaired daily functioning. Excessive threat-avoidance is a central diagnostic feature of anxiety disorders, yet little is known about whether avoidance acquired in the absence of a direct history of conditioning with a fearful event differs from directly learned avoidance. In the present study, we tested whether avoidance acquired indirectly via verbal instructions and symbolic generalization result in similar levels of avoidance behaviour and threat-beliefs to avoidance acquired after direct learning. Following fear conditioning in which one conditioned stimulus was paired with shock (CS+) and another was not (CS−), participants either learned or were instructed to make a response that cancelled impending shock. Three groups were then tested with a learned CS+ and CS− (learned group), instructed CS+ (instructed group), and generalized CS+ (derived group) presentations. Results showed similar levels of avoidance behaviour and threat-belief ratings about the likelihood of shock across each of the three pathways despite the different mechanisms by which they were acquired. Findings have implications for understanding the aetiology of clinical avoidance in anxiety.

According to estimates from Public Health England, by 2034 70% of adults are expected to be overweight or obese, therefore understanding the underpinning aetiology is a priority. Eating in response to negative affect contributes towards obesity, however, little is known about the underlying mechanisms. Evidence that visceral afferent signals contribute towards the experience of emotion is accumulating rapidly, with the emergence of new influential models of ‘active inference’. No longer viewed as a ‘bottom up’ process, new interoceptive facets based on ‘top down’ predictions have been proposed, although at present it is unclear which aspects of interoception contribute to aberrant eating behaviour and obesity. Study one examined the link between eating behaviour, body mass index and the novel interoceptive indices; interoceptive metacognitive awareness (IAw) and interoceptive prediction error (IPE), as well as the traditional measures; interoceptive accuracy (IAc) and interoceptive sensibility (IS). The dissociation between these interoceptive indices was confirmed. Emotional eaters were characterised by a heightened interoceptive signal but reduced meta-cognitive awareness of their interoceptive abilities. In addition, emotional eating correlated with IPE; effects that could not be accounted for by differences in anxiety and depression. Study two confirmed the positive association between interoceptive accuracy and emotional eating using a novel unbiased heartbeat discrimination task based on the method of constant stimuli. Results reveal new and important mechanistic insights into the processes that may underlie problematic affect regulation in overweight populations.

Humans responded on multiple random-ratio (RR) random-interval (RI) schedules, and their verbalized performance awareness (PA; i.e., their ability to accurately describe what they did) was measured in three experiments. In Experiment 1, instructions informed participants that to earn points, either sometimes rapid responding and sometimes slow responding would work best (accurate instructions); rapid responding would work best (go fast instructions); spaced responding would work best (go slow instructions); or no advice was provided (minimal instructions). In Experiments 2 and 3, participants received either accurate or minimal instructions and were subject to extinction after a multiple RR-RI schedule. In all experiments, both performance awareness, and receiving accurate instructions, were related to schedulesensitive responding, but were unrelated to one another -participants receiving accurate-rate instructions were not more likely to show performance awareness than those exposed to minimal instructions. Both higher performance awareness and exposure to accurate instructions predicted faster extinction in Experiment 2 but not in Experiment 3. The current results suggest that performance awareness rather than contingency awareness is more strongly related to humans displaying schedule-typical behavior and that this is not strongly related to any explicit verbal instructions that are given.

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