Visual attention and the acquisition of information in human crowds.

Pedestrian crowds can form the substrate of important socially contagious behaviors, including propagation of visual attention, violence, opinions, and emotional state. However, relating individual to collective behavior is often difficult, and quantitative studies have largely used laboratory experimentation. We present two studies in which we tracked the motion and head direction of 3,325 pedestrians in natural crowds to quantify the extent, influence, and context dependence of socially transmitted visual attention. In our first study, we instructed stimulus groups of confederates within a crowd to gaze up to a single point atop of a building. Analysis of passersby shows that visual attention spreads unevenly in space and that the probability of pedestrians adopting this behavior increases as a function of stimulus group size before saturating for larger groups. We develop a model that predicts that this gaze response will lead to the transfer of visual attention between crowd members, but it is not sufficiently strong to produce a tipping point or critical mass of gaze-following that has previously been predicted for crowd dynamics. A second experiment, in which passersby were presented with two stimulus confederates performing suspicious/irregular activity, supports the predictions of our model. This experiment reveals that visual interactions between pedestrians occur primarily within a 2-m range and that gaze-copying, although relatively weak, can facilitate response to relevant stimuli. Although the above aspects of gaze-following response are reproduced robustly between experimental setups, the overall tendency to respond to a stimulus is dependent on spatial features, social context, and sex of the passerby.

Should conservation strategies consider spatial generality? Farmland birds show regional not national patterns of habitat association.

A key assumption underlying any management practice implemented to aid wildlife conservation is that it will have similar effects on target species across the range it is applied. However, this basic assumption is rarely tested. We show that predictors [nearly all associated with agri-environment scheme (AES) options known to affect European birds] had similar effects for 11 bird species on sites with differing farming practice (pastoral vs. mixed farming) or which differed in the density at which the species was found. However, predictors from sites in one geographical region tended to have different effects in other areas suggesting that AES options targeted at a regional scale are more likely to yield beneficial results for farmland birds than options applied uniformly in national schemes. Our study has broad implications for designing conservation strategies at an appropriate scale, which we discuss.

Chick growth and prey quality in the European Bee-eater (Merops apiaster).

1. In each of four replicate experiments we fed three groups of bee-eater chicks for 24 h on different diets: bees, dragonflies, and a mixture of the two. 2. Dry weight assimilation efficiency did not differ between treatments and was in the region of 40-50%. Caloric assimilation efficiency was about 60% and did not differ significantly between diets. 3. Mean Growth efficiency (wt. gain/intake) was highest in all four replicates in chicks fed on the mixed diet. 4. When metabolic requirements are taken into account, growth efficiency on the mixed diet varies less with variation in intake than on the two pure diets. 5. The advantage of feeding chicks on a mixed diet may partly explain why parents do not show exclusive preferences for energy-maximising prey types.

The influence of emotional facial expressions on gaze-following in grouped and solitary pedestrians.

The mechanisms contributing to collective attention in humans remain unclear. Research indicates that pedestrians utilise the gaze direction of others nearby to acquire environmentally relevant information, but it is not known which, if any, additional social cues influence this transmission. Extending upon previous field studies, we investigated whether gaze cues paired with emotional facial expressions (neutral, happy, suspicious and fearsome) of an oncoming walking confederate modulate gaze-following by pedestrians moving in a natural corridor. We found that pedestrians walking alone were not sensitive to this manipulation, while individuals traveling together in groups did reliably alter their response in relation to emotional cues. In particular, members of a collective were more likely to follow gaze cues indicative of a potential threat (i.e., suspicious or fearful facial expression). This modulation of visual attention dependent on whether pedestrians are in social aggregates may be important to drive adaptive exploitation of social information, and particularly emotional stimuli within natural contexts.

Risk, uncertainty and regulation.

This paper reviews the relationship between scientific evidence, uncertainty, risk and regulation. Risk has many different meanings. Furthermore, if risk is defined as the likelihood of an event happening multiplied by its impact, subjective perceptions of risk often diverge from the objective assessment. Scientific evidence may be ambiguous. Scientific experts are called upon to assess risks, but there is often uncertainty in their assessment, or disagreement about the magnitude of the risk. The translation of risk assessments into policy is a political judgement that includes consideration of the acceptability of the risk and the costs and benefits of legislation to reduce the risk. These general points are illustrated with reference to three examples: regulation of risk from pesticides, control of bovine tuberculosis and pricing of alcohol as a means to discourage excessive drinking.

The gourmet ape: evolution and human food preferences.

This review explores the relation between evolution, ecology, and culture in determining human food preferences. The basic physiology and morphology of Homo sapiens sets boundaries to our eating habits, but within these boundaries human food preferences are remarkably varied, both within and between populations. This does not mean that variation is entirely cultural or learned, because genes and culture may coevolve to determine variation in dietary habits. This coevolution has been well elucidated in some cases, such as lactose tolerance (lactase persistence) in adults, but is less well understood in others, such as in favism in the Mediterranean and other regions. Genetic variation in bitter taste sensitivity has been well documented, and it affects food preferences (eg, avoidance of cruciferous vegetables). The selective advantage of this variation is not clear. In African populations, there is an association between insensitivity to bitter taste and the prevalence of malaria, which suggests that insensitivity may have been selected for in regions in which eating bitter plants would confer some protection against malaria. Another, more general, hypothesis is that variation in bitter taste sensitivity has coevolved with the use of spices in cooking, which, in turn, is thought to be a cultural tradition that reduces the dangers of microbial contamination of food. Our evolutionary heritage of food preferences and eating habits leaves us mismatched with the food environments we have created, which leads to problems such as obesity and type 2 diabetes.

The Croonian Lecture 2004 risk: food, fact and fantasy.

We all take risks, but most of the time we do not notice them. We are generally bad at judging the risks we take, and in the end, for some of us, this will prove fatal. Eating, like everything else in life, is not risk free. Is that next mouthful pure pleasure, or will it give you food poisoning? Will it clog your arteries as well as filling your stomach? This lecture weaves together three strands-the public understanding of science, the perception of risk and the role of science in informing government policy-as it explains how food risks are assessed and managed by government and explores the boundaries between the responsibilities of the individual and the regulator. In doing so, it draws upon the science of risk assessment as well as our attitudes to risk in relation to issues such as bovine spongiform encephalopathy, dioxins in salmon and diet and obesity.

Widespread local house-sparrow extinctions.

House-sparrow populations have declined sharply in Western Europe in recent decades, but the reasons for this decline have yet to be identified, despite intense public interest in the matter. Here we use a combination of field experimentation, genetic analysis and demographic data to show that a reduction in winter food supply caused by agricultural intensification is probably the principal explanation for the widespread local extinctions of rural house-sparrow populations in southern England. We show that farmland populations exhibit fine-level genetic structuring and that some populations are unable to sustain themselves (sinks), whereas others act as sources.