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Anxiety is a cluster of responses that can involve both operant and respondent behavior, which can be both public and/or private in nature, and occurs when an upcoming aversive stimulus is signaled. Despite the reported high comorbidity of autism and anxiety, there has been very limited research on how to directly assess and treat anxiety, especially with individuals who have limited communication skills. In Study 1, anxiety was assessed in five individuals with autism, ranging in age from 10 to 19 years old. Anxiety was assessed by measuring behavior during (1) a baseline (with no putative anxiety-provoking stimuli present), (2) signals for an upcoming aversive event, and (3) exposure to that aversive event. Anxiety presented in several different ways, as both conditioned activation and suppression, and both with and without problem behavior during the aversive event. In Study 2, individualized treatments involving differential reinforcement of alternative responses and stimulus fading were used to successfully reduce anxious responding in all four participants who displayed anxiety. These studies demonstrated a potentially useful means of assessing anxiety in individuals with autism which may not only help to measure anxious behavior and identify anxiety-provoking events, but may also lead to effective treatment.

The grouping behaviour of fish is a widespread phenomenon of high biological significance but little is known as to how consistent individual behavioural differences may affect group joining preferences. When given the option to join either a shy or a bold shoal of three-spined sticklebacks, Gasterosteus aculeatus, both shy and bold individuals showed a strong preference for associating with bold fish. Personality type interacted with individual hunger levels to affect the extent of association, suggesting important strategy variation by focal fish in a competitive foraging environment. Furthermore, shoals modified their behaviour in relation to the focal individual. Individual behavioural differences were shown to have a complex role in influencing association preferences as well as driving previously unrecognized behavioural modifications in foraging groups.

SummaryIn many animal groups, certain individuals consistently appear at the forefront of coordinated movements [1–4]. How such leaders emerge is poorly understood [5, 6]. Here, we show that in pairs of sticklebacks, Gasterosteus aculeatus, leadership arises from individual differences in the way that fish respond to their partner's movements. Having first established that individuals differed in their propensity to leave cover in order to look for food, we randomly paired fish of varying boldness, and we used a Markov Chain model to infer the individual rules underlying their joint behavior. Both fish in a pair responded to each other's movements—each was more likely to leave cover if the other was already out and to return if the other had already returned. However, we found that bolder individuals displayed greater initiative and were less responsive to their partners, whereas shyer individuals displayed less initiative but followed their partners more faithfully; they also, as followers, elicited greater leadership tendencies in their bold partners. We conclude that leadership in this case is reinforced by positive social feedback.

In a recent paper, we showed that leadership arises from individual behavioral differences in pairs of foraging stickleback (Gasterosteus aculeatus). Foraging data from randomly combined pairs of fish were analyzed using Markov Chain models to infer the individual movement rules underlying joint behavior. Whilst both fish responded to partner movement, bolder individuals were the least responsive and showed greater individual initiative. Shy partners were more faithful followers and were also found to bring about greater leadership tendencies in their bold partners. The ability of such followers to inspire bolder fish suggests that leadership may be dependent on individual temperament differences, reinforced by social feedback.