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Inhibitory control is one of several cognitive mechanisms required for self-regulation, decision making and attention towards tasks. Inhibitory control is expected to influence behavioural plasticity in animals, for example in the context of foraging, social interaction or responses to sudden changes in the environment. One widely used inhibitory control assay is the ‘detour task’ where subjects must avoid impulsively touching transparent barriers positioned in front of food, and instead access the food by an alternative but known route. However, because the detour task has been reported to measure factors unrelated to inhibitory control, including motivation, previous experience and persistence, the task may be unreliable for making cross-species comparisons, estimating individual differences and linking performance with socioecological traits. To address these concerns, we designed a variant of the detour task for wild great tits, Parus major, and deployed it at the nesting site across two spring seasons. We compared task performance of the same individuals in the wild across 2 years, and with their performance in captivity when tested using the classical cylinder detour task during the nonbreeding season. Potential confounds of motivation, previous experience, body size, sex, age and personality did not significantly predict performance, and temporal and contextual repeatability were low but significant. These results support the hypothesis that our assays captured intrinsic differences in inhibitory control. Instead of dismissing detour tasks and ‘throwing the baby out with the bathwater’, we suggest confounds are likely system and experimental-design specific, and that assays for this potentially fundamental but largely overlooked source of behavioural plasticity in animal populations, should be validated and refined for each study system.

Adapting to environmental change is a major challenge faced by animals and the role of individual behavioural differences in facilitating this process is currently the focus of much research. Innovation, the generation of a novel behaviour or use of a known behaviour in a novel context, is one form of behaviour that enables animals to respond to change. By deciphering the mechanisms underlying innovativeness, especially those that explain consistent differences between individuals, we can further understand the consequences of this behavioural variation. We tested whether motivation, experience, inhibitory control and personality were linked to different stages of sequential innovative problem-solving performance among great tits, Parus major, and of their overall innovativeness across tasks. We gave animals originating from lines bidirectionally selected for fast or slow early exploratory behaviour, a multiaccess problem-solving device. Diverse motor skills and behavioural flexibility were required to solve all three different access points sequentially over trials. Food-deprived, highly motivated birds had shorter latency to touch the device, were more likely to solve an access point within a trial, and solved a greater diversity of them, than their less motivated counterparts. Solving success increased with accuracy when interacting with the device (proportion of touches to functional components of the device compared to all touches to the device per trial), and with previous experience. Personality selection lines and inhibitory control had little effect. Repeatability analysis showed that between-individual differences in problem-solving performance were explained by: (1) pseudorepeatable effects (upward bias) linked to hunger-induced motivation, (2) repeatable differences in accuracy when interacting with devices, and (3) a feedback loop caused by experience gained over successive trials. Our results highlight the challenges of characterizing consistent individual differences in behaviour generally and support the idea that complex sources of variation play an important role in problem-solving performance.

Territorial animals often respond less aggressively to neighbours than strangers. This ‘dear enemy’ effect is hypothesized to be adaptive by reducing unnecessary aggressive interactions with non-threatening individuals. A key prediction of this hypothesis, that individual fitness will be affected by variation in the speed and the extent to which individuals reduce their aggression towards neighbours relative to strangers, has never been tested. We used a series of song playbacks to measure the change in response of male great tits to a simulated establishment of a neighbour on an adjacent territory during early stages of breeding, as an assay of individuals’ tendencies to form dear enemy relationships. Males reduced their approach to the speaker and sang fewer songs on later playback repetitions. However, only some males exhibited dear enemy behaviour by responding more strongly to a subsequent stranger playback, and when the playback procedure was repeated on a subset of males, there was some indication for consistent differences among individuals in the expression of dear enemy behaviour. We monitored nests and analysed offspring paternity to determine male reproductive success. Individuals that exhibited dear enemy behaviour towards the simulated neighbour did not suffer any costs associated with loss of paternity, but there was also no evidence of reproductive benefits, and no net effect on reproductive fitness. The general ability to discriminate between neighbours and strangers is likely adaptive, but benefits are probably difficult to detect because of the indirect link between individual variation in dear enemy behaviour and reproductive fitness and because of the complex range of mechanisms affecting relations with territorial neighbours. Significance statement: The dear enemy effect, in which animals respond less aggressively to familiar neighbours compared to strangers, is probably beneficial because it reduces aggressive interactions with non-threatening individuals. However, no study has ever tested whether there actually are fitness benefits for individuals with a greater tendency to form dear enemy relationships. Our study used experimental playbacks to simulate neighbours and strangers, and we found no relationship between dear enemy behaviour and reproductive success in a songbird. However, our approach to test adaptive hypotheses of this widespread territorial behaviour and our longitudinal playback design to examine the development of familiarity towards a neighbour and discrimination of neighbours and strangers are likely to be important tools to advance our understanding of territorial behaviour and individual recognition.

The producer-scrounger game is a key element of foraging ecology in many systems. Producing and scrounging typically covary negatively, but partitioning this covariance into contributions of individual plasticity and consistent between individual differences is key to understanding population-level consequences of foraging strategies. Furthermore, little is known about the role cognition plays in the producer-scrounger game. We investigated the role of cognition in these alternative foraging tactics in wild mixed-species flocks of great tits and blue tits, using a production learning task in which we measured individuals' speed of learning to visit the single feeder in an array that would provide them with a food reward. We also quantified the proportion of individuals' feeds that were scrounges ('proportion scrounged'); scrounging was possible if individuals visited immediately after a previous rewarded visitor. Three learning experiments-initial and two reversal learning-enabled us to estimate the repeatability and covariance of each foraging behaviour. First, we examined whether individuals learned to improve their scrounging success (i.e. whether they obtained food by scrounging when there was an opportunity to do so). Second, we quantified the repeatability of proportion scrounged, and asked whether proportion scrounged affected production learning speed among individuals. Third, we used multivariate analyses to partition within- and among-individual components of covariance between proportion scrounged and production learning speed. Individuals improved their scrounging success over time. Birds with a greater proportion scrounged took longer to learn their own rewarding feeder. Although multivariate analyses showed that covariance between proportion scrounged and learning speed was driven primarily by within-individual variation, that is, by behavioural plasticity, among-individual differences also played a role for blue tits. This is the first demonstration of a cognitive trait influencing producing and scrounging in the same wild system, highlighting the importance of cognition in the use of alternative resource acquisition tactics. The results of our covariance analyses suggest the potential for genetic differences in allocation to alternative foraging tactics, which are likely species- and system-dependent. They also point to the need to control for different foraging tactics when studying individual cognition in the wild.

Inhibitory control is one of several cognitive mechanisms required for self-regulation, decision making and attention towards tasks. Linked to a variety of maladaptive behaviours in humans, inhibitory control is expected to influence behavioural plasticity in animals in the context of foraging, social interaction, or responses to sudden changes in the environment. One widely used cognitive assay, the ‘detour task’, putatively tests inhibitory control. In this task, subjects must avoid impulsively touching transparent barriers positioned in front of food, and instead access the food by an alternative but known route. Recently it has been suggested that the detour task is unreliable and measures factors unrelated to inhibitory control, including motivation, previous experience and persistence. Consequently, there is growing uncertainty as to whether this task leads to erroneous interpretations about animal cognition and its links with socio-ecological traits. To address these outstanding concerns, we designed a variant of the detour task for wild great tits (Parus major) and deployed it at the nesting site of the same individuals across two spring seasons. This approach eliminated the use of food rewards, limited social confounds, and maximised motivation. We compared task performance in the wild with their performance in captivity when tested using the classical cylinder detour task during the non-breeding season. Task performance was temporally and contextually repeatable, and none of the confounds had any significant effect on performance, nor did they drive any of the observed repeatable differences among individuals. These results support the hypothesis that our assays captured intrinsic differences in inhibitory control. Instead of ‘throwing the detour task out with the bathwater’, we suggest confounds are likely system and experimental-design specific, and that assays for this potentially fundamental but largely overlooked source of behavioural plasticity in animal populations, should be validated and refined for each study system.

Territorial animals often respond less aggressively to neighbours than strangers. This ‘dear enemy’ effect is hypothesized to be adaptive by reducing unnecessary aggressive interactions with non-threatening individuals. A key prediction of this hypothesis, that individual fitness will be affected by variation in the speed and the extent to which individuals reduce their aggression towards neighbours relative to strangers, has never been tested. We used a series of song playbacks to measure the change in response of male great tits to a simulated establishment of a neighbour on an adjacent territory during early stages of breeding, as an assay of individuals’ tendencies to form dear enemy relationships. Males reduced their approach to the speaker and sang fewer songs on later playback repetitions. However, only some males exhibited dear enemy behaviour by responding more strongly to a subsequent stranger playback, and when the playback procedure was repeated on a subset of males, there was some indication for consistent differences among individuals in the expression of dear enemy behaviour. We monitored nests and analysed offspring paternity to determine male reproductive success. Individuals that exhibited dear enemy behaviour towards the simulated neighbour did not suffer any costs associated with loss of paternity, but there was also no evidence of reproductive benefits, and no net effect on reproductive fitness. The general ability to discriminate between neighbours and strangers is likely adaptive, but benefits are probably difficult to detect because of the indirect link between individual variation in dear enemy behaviour and reproductive fitness, and because of the complex range of mechanisms affecting relations with territorial neighbours.

The microbial community in the gut is influenced by environmental factors, especially diet, which can moderate host behaviour through the microbiome-gut-brain axis. However, the ecological relevance of microbiome-mediated behavioural plasticity in wild animals is unknown. We presented wild-caught great tits (Parus major) with a problem-solving task and showed that performance was weakly associated with variation in the gut microbiome. We then manipulated the gut microbiome by feeding birds one of two diets that differed in their relative levels of fat, protein and fibre content: an insect diet (low content), or a seed diet (high content). Microbial communities were less diverse among individuals given the insect compared to those on the seed diet. Individuals were less likely to problem-solve after being given the insect diet, and the same microbiota metrics that were altered as a consequence of diet were also those that correlated with variation in problem solving performance. Although the effect on problem-solving behaviour could have been caused by motivational or nutritional differences between our treatments, our results nevertheless raise the possibility that dietary induced changes in the gut microbiota could be an important mechanism underlying individual behavioural plasticity in wild populations.

Recent research in laboratory animals has illuminated how the vertebrate gut microbiome can have diverse and powerful effects on the brain and behaviour. However, the ecological relevance of this microbiome-gut-brain (MGB) axis outside the laboratory remains unexplored. Here we argue that understanding behavioural and cognitive effects of the gut microbiome in natural populations is an important goal for behavioural ecology that may shed light on the mechanisms and evolution of behavioural plasticity. We outline a toolkit of approaches that could be applied in this endeavour and argue that beyond collecting observational data on the microbiome and behaviour from free-living animals, the incorporation of manipulative approaches tailored to such systems will be a key next step to progress understanding in this area.

Natal body mass is a key predictor of viability and fitness in many animals. While variation in body mass and therefore juvenile viability may be explained by genetic and environmental factors, emerging evidence points to the gut microbiota as an important factor influencing host health. The gut microbiota is known to change during development, but it remains unclear whether the microbiome predicts fitness, and if it does, at which developmental stage it affects fitness traits.We collected data on two traits associated with fitness in wild nestling great tits (Parus major): weight and survival to fledging. We characterised the gut microbiome using 16S rRNA sequencing from nestling faeces and investigated temporal associations between the gut microbiome and fitness traits across development at day 8 (D8) and day 15 (D15) post-hatching. We also explored whether particular microbial taxa were ‘indicator species’ that reflected whether nestlings survived or not.There was no link between mass and microbial diversity on D8 or D15. However, we detected a time-lagged relationship where weight at D15 was negatively associated with the microbial diversity at D8, controlling for weight at D8, therefore reflecting relative weight gain over the intervening period.Indicator species analysis revealed that specificity values were high and fidelity values were low, suggesting that indicator taxa were primarily detected within either the survived or not survived groups, but not always detected in birds that either survived or died. Therefore these indicator taxa may be sufficient, but not necessary for determining either survival or mortality, perhaps owing to functional overlap in microbiota.We highlight that measuring microbiome-fitness relationships at just one time point may be misleading, especially early in life. Instead, microbial-host fitness effects may be best investigated longitudinally to detect critical development windows for key microbiota and host traits associated with neonatal weight. Our findings should inform future hypothesis testing to pinpoint which features of the gut microbial community impact on host fitness, and when during development this occurs. Such confirmatory research will shed light on population level processes and could have the potential to support conservation.

Although the evolution of cognitive differences among species has long been of interest in ecology, whether natural selection acts on cognitive processes within populations has only begun to receive similar attention. One of the key challenges is to understand how consistently cognitive traits within any one domain are expressed over time and across different contexts, as this has direct implications for the way in which selection might act on this variation. Animal studies typically measure a cognitive domain using only one task in one context, and assume that this captures the likely expression of that domain in different contexts. This deficit is not surprising because, from an ecologist’s perspective, cognitive tasks are notoriously laborious to employ, and for design reasons most tasks can only be deployed in a specific context. Thus our knowledge of whether individual differences in cognitive abilities are consistent across contexts is limited. Using a wild population of great tits (Parus major) we characterised consistency of two cognitive abilities, each in two different contexts: 1) spatial learning at two different spatial scales, and 2) behavioural flexibility as both performance in a detour reaching task and reversal learning in a spatial task. We found no evidence of a correlation between the two spatial learning speeds, or between the two measures of behavioural flexibility. This suggests that cognitive performance is highly plastic and sensitive to differences across tasks, or that variants of these well-known tasks may tap into different combinations of both cognitive and non-cognitive mechanisms, or that they simply do not adequately measure each putative cognitive domain. Our results highlight the challenges of developing standardised cognitive assays to explain natural behaviour and to understand the selective consequences of that variation.

Although the evolution of cognitive differences among species has long been of interest in ecology, whether natural selection acts on cognitive processes within populations has only begun to receive similar attention. One of the key challenges is to understand how consistently cognitive traits within any one domain are expressed over time and across different contexts, as this has direct implications for the way in which selection might act on this variation. Animal studies typically measure a cognitive domain using only one task in one context and assume that this captures the likely expression of that domain in different contexts. This use of limited and restricted measures is not surprising because, from an ecologist’s perspective, cognitive tasks are laborious to employ, and if the measure requires learning a particular aspect of the task (e.g., reward type, cue availability, scale of testing), then it is difficult to repeat the task as the learning is context specific. Thus, our knowledge of whether individual differences in cognitive abilities are consistent across contexts is limited, and current evidence suggests that consistency is weak. We tested up to 32 wild great tits (Parus major) to characterize the consistency of two cognitive abilities, each in two different contexts: 1) spatial cognition at two different spatial scales, and 2) behavioral flexibility as performance in a detour reaching task and reversal learning in a spatial task. We found no evidence of a correlation between individuals’ performance in two measures of spatial cognition or two measures of behavioral flexibility. This suggests that cognitive performance is highly plastic and sensitive to differences across tasks, that variants of these well-known tasks may tap into different combinations of both cognitive and non-cognitive mechanisms, or that the tasks simply do not adequately measure each putative cognitive domain. Our results highlight the challenges of developing standardized cognitive assays to explain natural behavior and to understand the selective consequences of that variation.

Cognition arguably drives most behaviours in animals, but whether and why individuals in the wild vary consistently in their cognitive performance is scarcely known, especially under mixed-species scenarios. One reason for this is that quantifying the relative importance of individual, contextual, ecological and social factors remains a major challenge. We examined how many of these factors, and sources of bias, affected participation and performance, in an initial discrimination learning experiment and two reversal learning experiments during self-administered trials in a population of great tits and blue tits. Individuals were randomly allocated to different rewarding feeders within an array. Participation was high and only weakly affected by age and species. In the initial learning experiment, great tits learned faster than blue tits. Great tits also showed greater consistency in performance across two reversal learning experiments. Individuals assigned to the feeders on the edge of the array learned faster. More errors were made on feeders neighbouring the rewarded feeder and on feeders that had been rewarded in the previous experiment. Our estimates of learning consistency were unaffected by multiple factors, suggesting that, even though there was some influence of these factors on performance, we obtained a robust measure of discrimination learning in the wild.

Urban ecosystems are not unique, as the ecological processes and anthropological effects they encapsulate can equally be found in a range of human dominated environments. Applying ecological lessons from both within and outside urban areas is important for insect conservation within our expanding towns and cities. The management of urban grasslands, which in many cases is controlled by private individual and corporate landowners, has the potential to make a large difference to the biodiversity they support. Here we report on an investigation of invertebrate biodiversity within a series of small urban grasslands with contrasting frequency of management by mowing. Seven gardens and five other grassland areas were suction sampled for grassland invertebrates in July 2016. Samples were taken in patches that were regularly cut on a 7-14 day cycle (very short), those cut every six weeks (short) and those than had not been cut since the previous year (long). Invertebrates were mostly identified to order level, with the Hemiptera to species or morphospecies. Invertebrate abundance was significantly inversely related to mowing frequency but overall species richness did not differ between short and very short grasslands. Community structure also was most distinct in the long grasslands. The pattern of abundance varied between different taxonomic groups, with the Hemiptera particularly benefiting from very low levels of management. The value to invertebrates, especially Hemiptera, of reduced grassland management is discussed, with reference to how the owners of gardens and other urban grassy areas can make simple changes to benefit biodiversity on their land

The microbial community in the gut is influenced by environmental factors, especially diet, which can moderate host behaviour through the microbiome-gut-brain axis. However, the ecological relevance of microbiome-mediated behavioural plasticity in wild animals is unknown. We presented wild-caught great tits (Parus major) with a problem-solving task and showed that performance was weakly associated with variation in the gut microbiome. We then manipulated the gut microbiome by feeding birds one of two diets that differed in their relative levels of fat, protein and fibre content: an insect diet (low content), or a seed diet (high content). Microbial communities were less diverse among individuals given the insect compared to those on the seed diet. Individuals were less likely to problem-solve after being given the insect diet, and the same microbiota metrics that were altered as a consequence of diet were also those that correlated with variation in problem solving performance. Although the effect on problem-solving behaviour could have been caused by motivational or nutritional differences between our treatments, our results nevertheless raise the possibility that dietary induced changes in the gut microbiota could be an important mechanism underlying individual behavioural plasticity in wild populations.

Research into proximate and ultimate mechanisms of individual cognitive variation in animal populations is a rapidly growing field that incorporates physiological, behavioural and evolutionary investigations. Recent studies in humans and laboratory animals have shown that the enteric microbial community plays a central role in brain function and development. The ‘gut–brain axis’ represents a multi-directional signalling system that encompasses neurological, immunological and hormonal pathways. In particular it is tightly linked with the hypothalamic–pituitary–adrenal axis (HPA), a system that regulates stress hormone release and influences brain development and function. Experimental examination of the microbiome through manipulation of diet, infection, stress and exercise, suggests direct effects on cognition, including learning and memory. However, our understanding of these processes in natural populations is extremely limited. Here, we outline how recent advances in predominantly laboratory-based microbiome research can be applied to understanding individual differences in cognition. Experimental manipulation of the microbiome across natal and adult environments will help to unravel the interplay between cognitive variation and the gut microbial community. Focus on individual variation in the gut microbiome and cognition in natural populations will reveal new insight into the environmental and evolutionary constraints that drive individual cognitive variation. This article is part of the theme issue ‘Causes and consequences of individual differences in cognitive abilities’.

Predator recognition is a prerequisite for antipredator behaviour. Although species level predator recognition is well documented, there is emerging evidence that some birds, including corvids, can differentiate between individual humans that pose different levels of threat. Other predator cues such as gaze direction may offer additional important information regarding the likelihood of an attack, but it is unknown whether wild animals can integrate information about the individual identity and gaze direction of a predator when perceiving threat levels. Here we measured wild jackdaws' responses to human head orientation, directed towards or away from their nestbox containing chicks. To test whether aversive responses to gaze direction were integrated with information about human identity, the human presenting gaze cues wore one of two masks: a ‘threatening’ mask that had previously been worn when handling the jackdaws' chicks and a ‘neutral mask’ that had previously been worn when walking by, but not disturbing the nest. Latency to return to the nestbox was significantly higher when the threatening mask rather than the neutral mask was worn, but it was not influenced by head direction. However, once a jackdaw landed outside the nestbox, there was a nonsignificant trend for it to be quicker to enter the box when the human was gazing towards, rather than away from the box. These results indicate that wild jackdaws can recognize different individual humans and thus differentiate between those wearing a threatening and a neutral mask, and respond defensively by guarding their chicks from potential threat. Jackdaws may integrate both predator identity and gaze cues; however, predation risk is primarily perceived through individual human recognition.

Sensitivity to the gaze of other individuals has long been a primary focus in sociocognitive research on humans and other animals. Information about where others are looking may often be of adaptive value in social interactions and predator avoidance, but studies across a range of taxa indicate there are substantial differences in the extent to which animals obtain and use information about other individuals' gaze direction. As the literature expands, it is becoming increasingly difficult to make comparisons across taxa as experiments adopt and adjust different methodologies to account for differences between species in their socioecology, sensory systems and possibly also their underlying cognitive mechanisms. Furthermore, as more species are found to exhibit gaze sensitivity, more terminology arises to describe the behaviours. To clarify the field, we propose a restricted nomenclature that defines gaze sensitivity in terms of observable behaviour, independent of the underlying mechanisms. This is particularly useful in nonhuman animal studies where cognitive interpretations are ambiguous. We then describe how socioecological factors may influence whether species will attend to gaze cues, and suggest links between ultimate factors and proximate mechanisms such as cognition and perception. In particular, we argue that variation in sensory systems, such as retinal specializations and the position of the eyes, will determine whether gaze cues (e.g. head movement) are perceivable during visual fixation. We end by making methodological recommendations on how to apply these variations in socioecology and visual systems to advance the field of gaze research.

Knowledge about the causal relationship between objects has been studied extensively in human infants, and more recently in adult animals using differential looking time experiments. How knowledge about object support develops in non-human animals has yet to be explored. Here, we studied the ontogeny of support relations in Eurasian jays (Garrulus glandarius), a bird species known for its sophisticated cognitive abilities. Using an expectancy violation paradigm, we measured looking time responses to possible and impossible video and image stimuli. We also controlled for experience with different support types to determine whether the emergence of support intuitions is dependent upon specific interactions with objects, or if reasoning develops independently. At age 9 months, birds looked more at a tool moving a piece of cheese that was not in contact than one that was in direct contact. By the age of 6 months, birds that had not experienced string as a support to hold up objects looked more at impossible images with string hanging from below (unsupported), rather than above (supported). The development of support intuitions may be independent of direct experience with specific support, or knowledge gained from interactions with other objects may be generalised across contexts.

Strong selection pressures are known to act on animal coloration. Although many animals vary in eye colour, virtually no research has investigated the functional significance of these colour traits. Passeriformes have a range of iris colours, making them an ideal system to investigate how and why iris colour has evolved. Using phylogenetic comparative methods, we tested the hypothesis that conspicuous iris colour in passerine birds evolved in response to (a) coordination of offspring care and (b) cavity nesting, two traits thought to be involved in intra-specific gaze sensitivity. We found that iris colour and cooperative offspring care by two or more individuals evolved independently, suggesting that bright eyes are not important for coordinating parental care through eye gaze. Furthermore, we found that evolution between iris colour and nesting behaviour did occur in a dependent manner, but contrary to predictions, transitions to coloured eyes were not more frequent in cavity nesters than non-cavity nesters. Instead, our results indicate that selection away from having bright eyes was much stronger in non-cavity nesters than cavity nesters, perhaps because conspicuous eye coloration in species not concealed within a cavity would be more visible to predators.

Mutations in the gene HSPB1, encoding the small heat shock protein 27 (HSP27), are a cause of distal hereditary motor neuropathy (dHMN) and axonal Charcot-Marie-Tooth disease (CMT2). dHMN and CMT2 are differentiated by the presence of a sensory neuropathy in the latter although in the case of HSPB1 this division is artificial as CMT2 secondary to HSPB1 mutations is predominantly a motor neuropathy with only minimal sensory involvement. A recent study in mice has suggested that mutations in the C-terminus result in a motor only phenotype resembling dHMN, whereas mutations at the N-terminus result in a CMT2-like phenotype. However, we present a family with a novel mutation in the C-terminus of HSP27 (p.Gln175X) [corrected] with a motor predominant distal neuropathy but with definite sensory involvement compatible with CMT2. This case highlights the artificial distinction between patients with motor predominant forms of CMT2 and dHMN and argues against the hypothesis that mutations in the C-terminus have no sensory involvement.

Background Charcot–Marie–Tooth disease (CMT) is a clinically and genetically heterogeneous group of diseases with approximately 45 different causative genes described. The aims of this study were to determine the frequency of different genes in a large cohort of patients with CMT and devise guidelines for genetic testing in practice. Methods The genes known to cause CMT were sequenced in 1607 patients with CMT (425 patients attending an inherited neuropathy clinic and 1182 patients whose DNA was sent to the authors for genetic testing) to determine the proportion of different subtypes in a UK population. Results A molecular diagnosis was achieved in 62.6% of patients with CMT attending the inherited neuropathy clinic; in 80.4% of patients with CMT1 (demyelinating CMT) and in 25.2% of those with CMT2 (axonal CMT). Mutations or rearrangements in PMP22 , GJB1 , MPZ and MFN2 accounted for over 90% of the molecular diagnoses while mutations in all other genes tested were rare. Conclusion Four commonly available genes account for over 90% of all CMT molecular diagnoses; a diagnostic algorithm is proposed based on these results for use in clinical practice. Any patient with CMT without a mutation in these four genes or with an unusual phenotype should be considered for referral for an expert opinion to maximise the chance of reaching a molecular diagnosis.

Attending to where others are looking is thought to be of great adaptive benefit for animals when avoiding predators and interacting with group members. Many animals have been reported to respond to the gaze of others, by co-orienting their gaze with group members (gaze following) and/or responding fearfully to the gaze of predators or competitors (i.e., gaze aversion). Much of the literature has focused on the cognitive underpinnings of gaze sensitivity, namely whether animals have an understanding of the attention and visual perspectives in others. Yet there remain several unanswered questions regarding how animals learn to follow or avoid gaze and how experience may influence their behavioral responses. Many studies on the ontogeny of gaze sensitivity have shed light on how and when gaze abilities emerge and change across development, indicating the necessity to explore gaze sensitivity when animals are exposed to additional information from their environment as adults. Gaze aversion may be dependent upon experience and proximity to different predator types, other cues of predation risk, and the salience of gaze cues. Gaze following in the context of information transfer within social groups may also be dependent upon experience with group-members; therefore we propose novel means to explore the degree to which animals respond to gaze in a flexible manner, namely by inhibiting or enhancing gaze following responses. We hope this review will stimulate gaze sensitivity research to expand beyond the narrow scope of investigating underlying cognitive mechanisms, and to explore how gaze cues may function to communicate information other than attention.

Animals often respond fearfully when encountering eyes or eye-like shapes. Although gaze aversion has been documented in mammals when avoiding group-member conflict, the importance of eye coloration during interactions between conspecifics has yet to be examined in non-primate species. Jackdaws ( Corvus monedula ) have near-white irides, which are conspicuous against their dark feathers and visible when seen from outside the cavities where they nest. Because jackdaws compete for nest sites, their conspicuous eyes may act as a warning signal to indicate that a nest is occupied and deter intrusions by conspecifics. We tested whether jackdaws’ pale irides serve as a deterrent to prospecting conspecifics by comparing prospectors’ behaviour towards nest-boxes displaying images with bright eyes (BEs) only, a jackdaw face with natural BEs, or a jackdaw face with dark eyes. The jackdaw face with BEs was most effective in deterring birds from making contact with nest-boxes, whereas both BE conditions reduced the amount of time jackdaws spent in proximity to the image. We suggest BEs in jackdaws may function to prevent conspecific competitors from approaching occupied nest sites.

Mutations in the gene HSPB1, encoding the small heat shock protein 27 (HSP27), are a cause of distal hereditary motor neuropathy (dHMN) and axonal Charcot-Marie-Tooth disease (CMT2). dHMN and CMT2 are differentiated by the presence of a sensory neuropathy in the latter although in the case of HSPB1 this division is artificial as CMT2 secondary to HSPB1 mutations is predominantly a motor neuropathy with only minimal sensory involvement. A recent study in mice has suggested that mutations in the C-terminus result in a motor only phenotype resembling dHMN, whereas mutations at the N-terminus result in a CMT2-like phenotype. However, we present a family with a novel mutation in the C-terminus of HSP27 (p.Gln175X) [corrected] with a motor predominant distal neuropathy but with definite sensory involvement compatible with CMT2. This case highlights the artificial distinction between patients with motor predominant forms of CMT2 and dHMN and argues against the hypothesis that mutations in the C-terminus have no sensory involvement.

The hereditary sensory and autonomic neuropathies (HSAN, also known as the hereditary sensory neuropathies) are a clinically and genetically heterogeneous group of disorders, characterised by a progressive sensory neuropathy often complicated by ulcers and amputations, with variable motor and autonomic involvement. To date, mutations in twelve genes have been identified as causing HSAN. To study the frequency of mutations in these genes and the associated phenotypes, we screened 140 index patients in our inherited neuropathy cohort with a clinical diagnosis of HSAN for mutations in the coding regions of SPTLC1, RAB7, WNK1/HSN2, FAM134B, NTRK1 (TRKA) and NGFB. We identified 25 index patients with mutations in six genes associated with HSAN (SPTLC1, RAB7, WNK1/HSN2, FAM134B, NTRK1 and NGFB); 20 of which appear to be pathogenic giving an overall mutation frequency of 14.3%. Mutations in the known genes for HSAN are rare suggesting that further HSAN genes are yet to be identified. The p.Cys133Trp mutation in SPTLC1 is the most common cause of HSAN in the UK population and should be screened first in all patients with sporadic or autosomal dominant HSAN.

The hereditary sensory and autonomic neuropathies (HSAN) are rare inherited neuropathies presenting with sensory loss and complications, including ulcers, infections, osteomyelitis and amputations. Usually, sensory symptoms predominate although motor involvement can occur. Autonomic features may be minimal (then hereditary sensory neuropathy, HSN, is preferred). HSAN has been classified into five subtypes depending on clinical presentation.1 Hereditary sensory and autonomic neuropathy II (HSANII or HSNII) is an early onset, autosomal recessive sensory neuropathy with ulcero-mutilating complications due to mutations in the HSN2 isoform of the WNK1 gene.2 Recently, a similar phenotype was described in a Saudi-Arabian family, and a homozygous nonsense mutation found in a new gene, FAM134B (family with sequence similarity 134, member B), encoding a newly identified Golgi protein. The index case in this family was initially thought to have leprosy. Three additional families (out of 75 patients) with similar phenotypes were found to have homozygous loss of function mutations in FAM134B.3 Here, we report the clinical and pathological findings in a further patient with HSNII due to a homozygous mutation in FAM134B. The patient (III-2) is from a consanguineous Somalian family (figure 1A) and had a normal birth and developmental milestones. She had recurrent foot infections and ulcers from the age of 5 years, and a right forefoot amputation aged 10 years. She started using a wheelchair aged 11 years. She described feeling pain and sweating normally. A cousin (III-7) had similar symptoms of recurrent infections and amputations. Figure 1 (A) Filled symbols=affected; empty symbols=unaffected; cross-slashed symbols=deceased; double line=consanguinity. The proband is indicated by the arrow. (B) Radiographs of the hands and ankles. (C–E) Sural …

The inherited neuropathies are a genetically and clinically heterogeneous group of disorders encompassing Charcot-Marie-Tooth disease (CMT), hereditary motor neuropathy (HMN) and hereditary sensory and autonomic neuropathy (HSAN). Mutations in over 45 genes have been implicated in causing the inherited neuropathies, and many more remain unknown. In order to determine the proportion of patients with inherited neuropathy attending our clinic who obtained a genetic diagnosis, we screened all known genes that cause CMT, HMN and HSAN. Of 871 patients attending a specialist neuropathy clinic over a 5-year period, 613 had an inherited neuropathy of whom 409 had CMT. A genetic diagnosis was reached in 59% of patients with CMT; 54% accounted for by chromosome 17 rearrangements or mutations in the commonly available genes PMP22, GJB1, MPZ and MFN2. A genetic diagnosis was achieved in 79% of patients with CMT1 and 35% of CMT2. The chromosome 17 duplication only accounted for 38% of CMT, less than reported in other populations; this reflects a bias in our clinic towards patients with rarer forms of CMT. We give details of the individual contributions the rarer genes made to our cohort. These results suggest that the majority of patients with CMT1 should obtain a genetic diagnosis. Mutations in the rarer known genes account for a small proportion of patients with CMT, and many genes for CMT2 remain unknown. We suggest an algorithm for genetic testing in patients with CMT in the UK.

This question has been so much discussed within the last few years, and so many are daily observing and studying the flight of every specimen of bird, that it is somewhat astonishing to me I have not yet come across any mention of the method which to my mind accounts for all the wonderful, and, to other theories, apparently impossible results of the ways of an eagle in air. I should be very glad to hear what objections can be raised to my explanation of how soaring is accomplished by any or all of the numerous writers and thinkers whose marvellous mathematical calculations enable them to account for some of the manoeuvres of birds to their own satisfaction. I have not yet seen any description of a theory which claims to account for every movement of all birds, but it must be admitted if any theory falls short of that, it cannot be correct; whilst if it fulfils that condition it cannot be very far wrong.