Fast and frugal framing effects?

Three experiments examine whether simple pair-wise comparison judgments, involving the “recognition heuristic” (Goldstein & Gigerenzer, 2002), are sensitive to implicit cues to the nature of the comparison required. Experiments 1 & 2 show that participants frequently choose the recognized option of a pair if asked to make “larger” judgments but are significantly less likely to choose the unrecognized option when asked to make “smaller” judgments. Experiment 3 demonstrates that, overall, participants consider recognition to be a more reliable guide to judgments of a magnitude criterion than lack of recognition and that this intuition drives the framing effect. These results support the idea that, when making pair-wise comparison judgments, inferring that the recognized item is large is simpler than inferring that the unrecognized item is small.

Less-is-more effects without the recognition heuristic

Inferences consistent with “recognition-based” decision-making may be drawn for various reasons other than recognition alone. We demonstrate that, for 2-alternative forced-choice decision tasks, less-is-more effects (reduced performance with additional learning) are not restricted to recognition-based inference but can also be seen in circumstances where inference is knowledge-based but item knowledge is limited. One reason why such effects may not be observed more widely is the dependence of the effect on specific values for the validity of recognition and knowledge cues. We show that both recognition and knowledge validity may vary as a function of the number of items recognized. The implications of these findings for the special nature of recognition information, and for the investigation of recognition-based inference, are discussed

Differences between naïve and expert observers’ vergence and accommodative responses to a range of targets

Purpose: Vergence and accommodation studies often use adult participants with experience of vision science. Reports of infant and clinical responses are generally more variable and of lower gain, with the implication that differences lie in immaturity or sub-optimal clinical characteristics but expert/naïve differences are rarely considered or quantified. Methods: Sixteen undergraduates, naïve to vision science, were individually matched by age, visual acuity, refractive error, heterophoria, stereoacuity and near point of accommodation to second- and third-year orthoptics and optometry undergraduates (‘experts’). Accommodation and vergence responses were assessed to targets moving between 33 cm, 50 cm, 1 m and 2 m using a haploscopic device incorporating a PlusoptiX SO4 autorefractor. Disparity, blur and looming cues were separately available or minimised in all combinations. Instruction set was minimal. Results: In all cases, vergence and accommodation response slopes (gain) were steeper and closer to 1.0 in the expert group (p = 0.001), with the largest expert/naïve differences for both vergence and accommodation being for near targets (p = 0.012). For vergence, the differences between expert and naïve response slopes increased with increasingly open-loop targets (linear trend p = 0.025). Although we predicted that proximal cues would drive additional response in the experts, the proximity-only cue was the only condition that showed no statistical effect of experience. Conclusions: Expert observers provide more accurate responses to near target demand than closely matched naïve observers. We suggest that attention, practice, voluntary and proprioceptive effects may enhance responses in experienced participants when compared to a more typical general population. Differences between adult reports and the developmental and clinical literature may partially reflect expert/naïve effects, as well as developmental change. If developmental and clinical studies are to be compared to adult normative data, uninstructed naïve adult data should be used.

The roles of olfaction and vision in host-plant finding by the diamondback moth, Plutella xylostella

The relative roles of olfaction and vision in the crepuscular host-finding process of a major lepidopteran pest of cruciferous crops, the diamondback moth Plutella xylostella are investigated in a series of laboratory and semi-field experiments. Flying female moths use volatile plant chemical cues to locate and to promote landing on their host, even in complex mixed-crop environments in large cages. Multiple regression analysis shows that both the plant position (front, middle or back rows) and the type of plant (host plant, nonhost plant) are needed to explain the distribution of insects in such a mixed-crop situation. This strong plant position effect indicates that, when host plants are present in a mixture, foraging P. xylostella are more likely to alight on the first row of the plants. The findings are discussed with regard to current theories of host-plant location by phytophagous insects and the possible implications for integrated pest management.

Very short delays prior to escape from potential predators may function efficiently as adaptive risk-assessment periods

Periods between predator detection and an escape response (escape delays) by prey upon attack by a predator often arise because animals trade-off the benefits such a delay gives for assessing risk accurately with the costs of not escaping as quickly as possible. We tested whether freezing behaviour (complete immobility in a previously foraging bird) observed in chaffinches before escaping from an approaching potential threat functions as a period of risk-assessment, and whether information on predator identity is gained even when time available is very short. We flew either a model of a sparrowhawk (predator) or a woodpigeon (no threat) at single chaffinches. Escape delays were significantly shorter with the hawk, except when a model first appeared close to the chaffinch. Chaffinches were significantly more vigilant when they resumed feeding after exposure to the sparrowhawk compared to the woodpigeon showing that they were able to distinguish between threats, and this applied even when time available for assessment was short (an average of 0.29 s). Our results show freezing in chaffinches functions as an effective economic risk assessment period, and that threat information is gained even when very short periods of time are available during an attack.

Domestically produced food: Consumer perceptions of origin, safety and the issue of trust

It is becoming increasingly difficult for the public to attempt to assess risks using traditional methods such as smell, taste or other physical attributes of food. The existence of extrinsic cues such as the country of origin (COO) of food can help to make food purchase decisions easier for consumers. However, the use of extrinsic cues depends heavily on the extent to which consumers trust such signals to be indicative of quality or safety, which in turn depends on the credibility behind that cue. This paper aims to examine consumers association of domestically produced food with increased food safety standards and the association of COO and food safety information with socio-demographics and other aspects of consumer psychology such as attitudes, risk perception and trust. Using an ordered probit model, domestic production is examined as an extrinsic cue for food safety by looking at the relationship with trust in food safety information provided by national food standards agencies (NFSAs) and other socio-demographic characteristics, based on nationally representative data from 2725 face-to-face interviews across five European countries. Results suggest that domestic production of food is an extrinsic cue for food safety and as consumers place increasing importance on food safety they are more interested in food produced in their own country. This, coupled with consumer trust in a strong, and independent national food standards agency, suggests the potential exists for the increased consumption of domestically produced foods.

The effects of non-host plant essential oil volatiles on the behaviour of the pollen beetle Meligethes aeneus

The use of semiochemicals for manipulation of the pollen beetle Meligethes aeneus (Fabricius) (Coleoptera: Nitidulidae) is being investigated for potential incorporation into a push-pull control strategy for this pest, which damages oilseed rape, Brassica napus L. (Brassicaceae), throughout Europe. The response of M. aeneus to non-host plant volatiles was investigated in laboratory assays to establish whether they have any effect on host plant location behaviour. Two approaches were used. First a novel, moving-air bioassay using air funnels was developed to compare the response of M. aeneus to several non-host plant essential oils. The beetles avoided the host plant flowers in the presence of non-host volatiles, suggesting that M. aeneus uses olfactory cues in host location and/or acceptance. The results were expressed as 'repellency values' in order to compare the effects of the different oils tested. Lavender (Lavendula angustifolia Miller) (Lamiaceae) essential oil gave the highest repellency value. In addition, a four-arm olfactometer was used to investigate olfactory responses, as this technique eliminated the influence of host plant visual and contact cues. The attraction to host plant volatiles was reduced by the addition of non-host plant volatiles, but in addition to masking the host plant volatiles, the non-host volatiles were avoided when these were presented alone. This is encouraging for the potential use of non-host plants within a push-pull strategy to reduce the pest colonisation of crops. Further testing in more realistic semi-field and field trials is underway.

Post-dispersal seed predation of non-target weeds in arable crops

Field experiments were conducted to quantify the natural levels of post-dispersal seed predation of arable weed species in spring barley and to identify the main groups of seed predators. Four arable weed species were investigated that were of high biodiversity value, yet of low to moderate competitive ability with the crop. These were Chenopodium album, Sinapis arvensis, Stellaria media and Polygonum aviculare. Exclusion treatments were used to allow selective access to dishes of seeds by different predator groups. Seed predation was highest early in the season, followed by a gradual decline in predation over the summer for all species. All species were taken by invertebrates. The activity of two phytophagous carabid genera showed significant correlations with seed predation levels. However, in general carabid activity was not related to seed predation and this is discussed in terms of the mainly polyphagous nature of many Carabid species that utilized the seed resource early in the season, but then switched to carnivory as prey populations increased. The potential relevance of post-dispersal seed predation to the development of weed management systems that maximize biological control through conservation and optimize herbicide use, is discussed.

Can arable field margins be managed to enhance their biodiversity, conservation and functional value for soil macrofauna?

1. The establishment of grassy strips at the margins of arable fields is an agri-environment scheme that aims to provide resources for native flora and fauna and thus increase farmland biodiversity. These margins can be managed to target certain groups, such as farmland birds and pollinators, but the impact of such management on the soil fauna has been poorly studied. This study assessed the effect of seed mix and management on the biodiversity, conservation and functional value of field margins for soil macrofauna. 2. Experimental margin plots were established in 2001 in a winter wheat field in Cambridgeshire, UK, using a factorial design of three seed mixes and three management practices [spring cut, herbicide application and soil disturbance (scarification)]. In spring and autumn 2005, soil cores taken from the margin plots and the crop were hand-sorted for soil macrofauna. The Lumbricidae, Isopoda, Chilopoda, Diplopoda, Carabidae and Staphylinidae were identified to species and classified according to feeding type. 3. Diversity in the field margins was generally higher than in the crop, with the Lumbricidae, Isopoda and Coleoptera having significantly more species and/or higher abundances in the margins. Within the margins, management had a significant effect on the soil macrofauna, with scarified plots containing lower abundances and fewer species of Isopods. The species composition of the scarified plots was similar to that of the crop. 4. Scarification also reduced soil- and litter-feeder abundances and predator species densities, although populations appeared to recover by the autumn, probably as a result of dispersal from neighbouring plots and boundary features. The implications of the responses of these feeding groups for ecosystem services are discussed. 5. Synthesis and applications. This study shows that the management of agri-environment schemes can significantly influence their value for soil macrofauna. In order to encourage the litter-dwelling invertebrates that tend to be missing from arable systems, agri-environment schemes should aim to minimize soil cultivation and develop a substantial surface litter layer. However, this may conflict with other aims of these schemes, such as enhancing floristic and pollinator diversity.

Predators of Spotted Flycatcher Muscicapa striata nests in southern England as determined by digital nest cameras

Capsule Avian predators are principally responsible. Aims To document the fate of Spotted Flycatcher nests and to identify the species responsible for nest predation. Methods During 2005-06, purpose-built, remote, digital nest-cameras were deployed at 65 out of 141 Spotted Flycatcher nests monitored in two study areas, one in south Devon and the second on the border of Bedfordshire and Cambridgeshire. Results Of the 141 nests monitored, 90 were successful (non-camera nests, 49 out of 76 successful, camera nests, 41 out of 65). Fate was determined for 63 of the 65 nests monitored by camera, with 20 predation events documented, all of which occurred during daylight hours. Avian predators carried out 17 of the 20 predations, with the principal nest predator identified as Eurasian Jay Garrulus glandarius. The only mammal recorded predating nests was the Domestic Cat Felis catus, the study therefore providing no evidence that Grey Squirrels Sciurus carolinensis are an important predator of Spotted Flycatcher nests. There was no evidence of differences in nest survival rates at nests with and without cameras. Nest remains following predation events gave little clue as to the identity of the predator species responsible. Conclusions Nest-cameras can be useful tools in the identification of nest predators, and may be deployed with no subsequent effect on nest survival. The majority of predation of Spotted Flycatcher nests in this study was by avian predators, principally the Jay. There was little evidence of predation by mammalian predators. Identification of specific nest predators enhances studies of breeding productivity and predation risk.

Predation of Bradysia sp (Diptera: Sciaridae), Liriomyza trifolii (Diptera: Agromyzidae) and Bemisia tabaci (Hemiptera: Aleyrodidae) by Coenosia attenuata (Diptera: Muscidae) in greenhouse crops

We studied the predation behaviour of the "hunter fly" (Coenosia attenuata Stein) in the laboratory and greenhouse. In the laboratory, which was conducted at 25 degrees C at 60-80% RH, with a 16L : 8D photoperiod, we examined the functional response of this species to three different pests, namely the sciarid fly (Bradysia sp.), the tobacco whitefly (Bemisia tabaci) and the leaf miner Liriomyza trifolii. In the greenhouse, we studied the population dynamics of the predator and its prey on pepper and water melon crops grown in southern Spain. Adult hunter flies were found to exhibit a type I functional response to adult sciarid flies and whiteflies, but a type II response to adult leaf miners. The type II response was a result of the greater difficulty in capturing and handling leaf miners compared to the other two species. The dynamics of the predator-prey interaction in the greenhouse revealed that the predator specializes mainly on adult sciarids and that the presence of the other prey can be supplemental, but is never essential for survival of the predator; this, however, is crop-dependent. The results oil the dynamics of the predator-prey systems were obtained through a known population dynamics model with modifications.

Intra-specific variation affects the structure of the natural enemy assemblage attacking pea aphid colonies

1. Intra-specific variation in plant defence traits has been shown to profoundly affect herbivore community structure. Here we describe two experiments designed to test whether similar effects occur at higher trophic levels, by studying pea aphid–natural enemy interactions in a disused pasture in southern England. 2. In the first experiment, the numbers and identity of natural enemies attacking different monoclonal pea aphid colonies were recorded in a series of assays throughout the period of pea aphid activity. 3. In the summer assay, there was a significant effect of clone on the numbers of aphidophagous hoverfly larvae and the total number of non-hoverfly natural enemies recruited. Clone also appeared to influence the attack rate suffered by the primary predator in the system, the hoverfly Episyrphus balteatus, by Diplazon laetatorius, an ichneumonid parasitoid. Colonies were generally driven to extinction by hoverfly attack, resulting in the recording of low numbers of parasitoids and entomopathogens, suggesting intense intra-guild predation. 4. To further examine the influence of clonal variation on the recruitment of natural enemies, a second experiment was performed to monitor the temporal dynamics of community development. Colonies were destructively sampled every other day and the numbers of natural enemies attacking aphid colonies were recorded. These data demonstrated that clonal variation influenced the timing, abundance, and identity of natural enemies attacking aphid colonies. 5. Taken together, these data suggest that clonal variation may have a significant influence on the patterns of interactions between aphids and their natural enemies, and that such effects are likely to affect our understanding of the ecology and biological control of these insect herbivores.

Terrestrial carnivores and human food production: impact and management

1. The production of food for human consumption has led to an historical and global conflict with terrestrial carnivores, which in turn has resulted in the extinction or extirpation of many species, although some have benefited. At present, carnivores affect food production by: (i) killing human producers; killing and/or eating (ii) fish/shellfish; (iii) game/wildfowl; (iv) livestock; (v) damaging crops; (vi) transmitting diseases; and (vii) through trophic interactions with other species in agricultural landscapes. Conversely, carnivores can themselves be a source of dietary protein (bushmeat). 2. Globally, the major areas of conflict are predation on livestock and the transmission of rabies. At a broad scale, livestock predation is a customary problem where predators are present and has been quantified for a broad range of carnivore species, although the veracity of these estimates is equivocal. Typically, but not always, losses are small relative to the numbers held, but can be a significant proportion of total livestock mortality. Losses experienced by producers are often highly variable, indicating that factors such as husbandry practices and predator behaviour may significantly affect the relative vulnerability of properties in the wider landscape. Within livestock herds, juvenile animals are particularly vulnerable. 3. Proactive and reactive culling are widely practised as a means to limit predation on livestock and game. Historic changes in species' distributions and abundance illustrate that culling programmes can be very effective at reducing predator density, although such substantive impacts are generally considered undesirable for native predators. However, despite their prevalence, the effectiveness, efficiency and the benefit:cost ratio of culling programmes have been poorly studied. 4. A wide range of non-lethal methods to limit predation has been studied. However, many of these have their practical limitations and are unlikely to be widely applicable. 5. Lethal approaches are likely to dominate the management of terrestrial carnivores for the foreseeable future, but animal welfare considerations are increasingly likely to influence management strategies. The adoption of non-lethal approaches will depend upon proof of their effectiveness and the willingness of stakeholders to implement them, and, in some cases, appropriate licensing and legislation. 6. Overall, it is apparent that we still understand relatively little about the importance of factors affecting predation on livestock and how to manage this conflict effectively. We consider the following avenues of research to be essential: (i) quantified assessments of the loss of viable livestock; (ii) landscape-level studies of contiguous properties to quantify losses associated with variables such as different husbandry practices; (iii) replicated experimental manipulations to identify the relative benefit of particular management practices, incorporating (iv) techniques to identify individual predators killing stock; and (v) economic analyses of different management approaches to quantify optimal production strategies.

The role of exotic plants in the invasion of Seychelles by the polyphagous insect Aleurodicus disperses: a phylogenetically controlled analysis

The accidental introduction of the spiralling whitefly, Aleurodicus dispersus Russell (Homoptera: Aleyrodidae) to Seychelles in late 2003 is exploited during early 2005 to study interactions between A. dispersus, native and exotic host plants and their associated arthropod fauna. The numbers of A. dispersus egg spirals and pupae, predator and herbivore taxa were recorded for eight related native/exotic pairs of host plants found on Mahe, the largest island in Seychelles. Our data revealed no significant difference in herbivore density (excluding A. dispersus) between related native and exotic plants, which suggests that the exotic plants do not benefit from 'enemy release'. There were also no differences in predator density, or combined species richness between native and exotic plants. Together these data suggest that 'biotic resistance' to invasion is also unlikely. Despite the apparent lack of differences in community structure significantly fewer A. dispersus egg spirals and pupae were found on the native plants than on the exotic plants. Additional data on A. dispersus density were collected on Cousin Island, a managed nature reserve in which exotic plants are carefully controlled. Significantly higher densities of A. dispersus were observed on Mahe, where exotic plants are abundant, than on Cousin. These data suggest that the rapid invasion of Seychelles by A. dispersus may largely be due to the high proportion of plant species that are both exotic and hosts of A. dispersus; no support was found for either the 'enemy release' or the 'biotic resistance' hypotheses.

Avoidance responses of an aphidophagous ladybird, Adalia bipunctata, to aphid-tending ants

1. Insect predators often aggregrate to patches of high prey density and use prey chemicals as cues for oviposition. If prey have mutualistic guardians such as ants, however, then these patches may be less suitable for predators. 2. Ants often tend aphids and defend them against predators such as ladybirds. Here, we show that ants can reduce ladybird performance by destroying eggs and physically attacking larvae and adults. 3. Unless ladybirds are able to defend against ant attacks they are likely to have adaptations to avoid ants. We show that Adalia bipunctata ladybirds not only move away from patches with Lasius niger ants, but also avoid laying eggs in these patches. Furthermore, ladybirds not only respond to ant presence, but also detect ant semiochemicals and alter oviposition strategy accordingly. 4. Ant semiochemicals may signal the extent of ant territories allowing aphid predators to effectively navigate a mosaic landscape of sub-optimal patches in search of less well-defended prey. Such avoidance probably benefits both ants and ladybirds, and the semiochemicals could be regarded as a means of cooperative communication between enemies. 5. Overall, ladybirds respond to a wide range of positive and negative oviposition cues that may trade-off with each other and internal motivation to determine the overall oviposition strategy.