The forest or the trees: preference for global over local image processing is reversed by prior experience in honeybees

The modelling of flower colour: spectral purity or colour contrast as biologically relevant descriptors of flower colour signals for bees depending upon the perceptual task

Flower colour is an important mediator of plant-pollinator interactions. While the reflectance of light from the flower surface and background are governed by physical properties, the perceptual interpretation of such information is generated by complex multilayered visual processing. Should quantitative modelling of flower signals strive for repeatable consistency enabled by parameter simplification, or should modelling reflect the dynamic way in which bees are known to process signals? We discuss why colour is an interpretation of spectral information by the brain of an animal. Different species, or individuals within a species, may respond differently to colour signals depending on sensory apparatus and/or individual experience. Humans and bees have different spectral ranges, but colour theory is strongly rooted in human colour perception and many principles of colour vision appear to be common. We discuss bee colour perception based on physiological, neuroanatomical and behavioural evidence to provide a pathway for modelling flower colours. We examine whether flower petals and floral guides as viewed against spectrally different backgrounds should be considered as a simple colour contrast problem or require a more dynamic consideration of how bees make perceptual decisions. We discuss that plants such as deceptive orchids may present signals to exploit bee perception, whilst many plants do provide honest signalling where perceived saturation indicates the probability of collecting nutritional rewards towards the centre of a flower that then facilitates effective pollination.

Some like it "local": A review of hierarchical processing in non-human animals

When seeing a visual image, humans prioritize the perception of global features, which is followed by the assessment of the local ones. This global precedence has been investigated using hierarchical stimuli that consist of a large, global shape formed by the spatial arrangement of small local shapes. Comparing non-human animals to humans, research on global and local processing has revealed a heterogeneous pattern of results with some species exhibiting a local precedence and others a global one. Many factors have been proposed to influence the global and local processing: internal factors (e.g., age, sex) and external elements or perceptual field variables (e.g., stimulus size, visual angle, eccentricity, sparsity). In this review, studies showing that different non-human species process hierarchical stimuli in the same (global precedence) or reverse (local precedence) direction as humans are first collated. Different ecological, perceptual, and anatomical features that may influence global and local processing are subsequently proposed based on a detailed analysis of these studies. This information is likely to improve our understanding of the mechanisms behind the perceptual organization and visual processing, and could explain the observed differences in hierarchical processing between species.

Do cows see the forest or the trees? A preliminary investigation of attentional scope as a potential indicator of emotional state in dairy cows housed with their calves

A positive mood in humans tends to broaden attentional scope while negative mood narrows it. A similar effect may be present in non-human animals; therefore, attentional scope may be a novel method to assess emotional states in livestock. In this proof-of-concept exploratory study, we examined the attentional scope of dairy cows housed with their calves either full-time, part-time (during daytime only), or with no calf contact (enrolled n = 10 each). Housing conditions were previously verified to induce differences in positive and negative emotional state, where part-time was considered more negative. Cows were trained to approach or avoid hierarchical images on a screen that were consistent in local and global elements (i.e., 13 small circles or crosses arranged in an overall circle or cross). After discrimination learning (>80% correct, over two consecutive days), 14 cows proceeded to test (n = 6 each full-and part-time; n = 2 no-contact, not analyzed). Test images showed inconsistent combinations of global and local elements (i.e., the overall global shape differs from the smaller local elements, such as a global circle composed of smaller local crosses and vice versa). Over two test days, approach responses to global and local images (each presented four times) were recorded. All cows were more likely to approach the local than the global image, especially part-time cows who never approached the global image; this may reflect a narrowed attentional scope in these cows. Full-time cows approached images more often than part-time cows, but overall response rates to global and local images were low, making specific conclusions regarding attentional scope difficult. Different housing conditions have potential to affect attentional scope, and possibly emotional state, of dairy cows, but statistical comparison to no-contact treatment was not possible. Cortisol concentration did not affect responses to images; thus arousal due to treatment or test conditions could not explain test performance. Further work with refined methodology and a larger sample size is required to validate the reliability of attentional scope as an assessment method of emotional state in cattle. Beyond this, the attentional scope test revealed how cattle may process, learn and respond to different visual hierarchical images, which further our understanding of cognitive and visual processes in cattle.

Humans, fish, spiders and bees inherited working memory and attention from their last common ancestor

All brain processes that generate behaviour, apart from reflexes, operate with information that is in an "activated" state. This activated information, which is known as working memory (WM), is generated by the effect of attentional processes on incoming information or information previously stored in short-term or long-term memory (STM or LTM). Information in WM tends to remain the focus of attention; and WM, attention and STM together enable information to be available to mental processes and the behaviours that follow on from them. WM and attention underpin all flexible mental processes, such as solving problems, making choices, preparing for opportunities or threats that could be nearby, or simply finding the way home. Neither WM nor attention are necessarily conscious, and both may have evolved long before consciousness. WM and attention, with similar properties, are possessed by humans, archerfish, and other vertebrates; jumping spiders, honey bees, and other arthropods; and members of other clades, whose last common ancestor (LCA) is believed to have lived more than 600 million years ago. It has been reported that very similar genes control the development of vertebrate and arthropod brains, and were likely inherited from their LCA. Genes that control brain development are conserved because brains generate adaptive behaviour. However, the neural processes that generate behaviour operate with the activated information in WM, so WM and attention must have existed prior to the evolution of brains. It is proposed that WM and attention are widespread amongst animal species because they are phylogenetically conserved mechanisms that are essential to all mental processing, and were inherited from the LCA of vertebrates, arthropods, and some other animal clades.

Investigating attentional scope as a novel indicator of emotional state in animals

In humans, contrasting emotional states can lead to a broadening or narrowing of attentional scope. Whether this is also the case in animals has yet to be investigated. If confirmed, measurement of attentional scope has potential as a novel cognitive method of welfare assessment. In this study, we therefore aimed to investigate a test of attentional scope as a measure of emotional state in animals. We did this by inducing four putatively different emotional states in dogs (N = 10), varying in valence (positive, negative) and arousal (high, low), in two different reward contexts (food rewards in Experiment 1, social rewards in Experiment 2) and then assessing dogs' behavioural responses in a test of attentional scope. We also recorded heart rate variability (HRV) parameters as additional confirmatory affective indicators. In Experiment 1, the dogs showed a narrowing of attentional scope after the induction of both positively valenced emotional states. That dogs were in a positive state was supported by the reduced Standard Deviation of normal-to-normal R-R intervals (SDNN) and the reduced Low Frequency (LF) and Very Low Frequency (VLF) HRV. In Experiment 2, when responses to social rewards were examined, we did not detect any statistically significant differences in attentional scope between the emotional states, but dogs had a slightly narrow attentional scope in the negatively valenced emotional states. The LF tended to be reduced in the high arousal positive treatment. In conclusion, our study provides the first indication that emotional states can also alter attentional scope in animals. The results justify further investigation of this approach for use in animal welfare assessment, although additional studies are needed to refine predictions.

Illusional Perspective across Humans and Bees

For two centuries, visual illusions have attracted the attention of neurobiologists and comparative psychologists, given the possibility of investigating the complexity of perceptual mechanisms by using relatively simple patterns. Animal models, such as primates, birds, and fish, have played a crucial role in understanding the physiological circuits involved in the susceptibility of visual illusions. However, the comprehension of such mechanisms is still a matter of debate. Despite their different neural architectures, recent studies have shown that some arthropods, primarily Hymenoptera and Diptera, experience illusions similar to those humans do, suggesting that perceptual mechanisms are evolutionarily conserved among species. Here, we review the current state of illusory perception in bees. First, we introduce bees' visual system and speculate which areas might make them susceptible to illusory scenes. Second, we review the current state of knowledge on misperception in bees (Apidae), focusing on the visual stimuli used in the literature. Finally, we discuss important aspects to be considered before claiming that a species shows higher cognitive ability while equally supporting alternative hypotheses. This growing evidence provides insights into the evolutionary origin of visual mechanisms across species.

Spontaneous choices for insect-pollinated flower shapes by wild non-eusocial halictid bees

The majority of angiosperms require animal pollination for reproduction, and insects are the dominant group of animal pollinators. Bees are considered one of the most important and abundant insect pollinators. Research into bee behaviour and foraging decisions has typically centred on managed eusocial bee species, including Apis mellifera and Bombus terrestris. Non-eusocial bees are understudied with respect to foraging strategies and decision making, such as flower preferences. Understanding whether there are fundamental foraging strategies and preferences that are features of insect groups can provide key insights into the evolution of flower-pollinator co-evolution. In the current study, Lasioglossum (Chilalictus) lanarium and Lasioglossum (Parasphecodes) sp., two native Australian generalist halictid bees, were tested for flower shape preferences between native insect-pollinated and bird-pollinated flowers. Each bee was presented with achromatic images of either insect-pollinated or bird-pollinated flowers in a circular arena. Both native bee species demonstrated a significant preference for images of insect-pollinated flowers. These preferences are similar to those found in A. mellifera, suggesting that flower shape preference may be a deep-rooted evolutionary occurrence within bees. With growing interest in the sensory capabilities of non-eusocial bees as alternative pollinators, the current study also provides a valuable framework for further behavioural testing of such species.

Wild non-eusocial bees learn a colour discrimination task in response to simulated predation events

Despite representing the majority of bee species, non-eusocial bees (e.g. solitary, subsocial, semisocial, and quasisocial species) are comparatively understudied in learning, memory, and cognitive-like behaviour compared to eusocial bees, such as honeybees and bumblebees. Ecologically relevant colour discrimination tasks are well-studied in eusocial bees, and research has shown that a few non-eusocial bee species are also capable of colour learning and long-term memory retention. Australia hosts over 2000 native bee species, most of which are non-eusocial, yet evidence of cognitive-like behaviour and learning abilities under controlled testing conditions is lacking. In the current study, I examine the learning ability of a non-eusocial Australian bee, Lasioglossum (Chilalictus) lanarium, using aversive differential conditioning during a colour discrimination task. L. lanarium learnt to discriminate between salient blue- and yellow-coloured stimuli following training with simulated predation events. This study acts as a bridge between cognitive studies on eusocial and non-social bees and introduces a framework for testing non-eusocial wild bees on elemental visual learning tasks using aversive conditioning. Non-eusocial bee species are far more numerous than eusocial species and contribute to agriculture, economics, and ecosystem services in Australia and across the globe. Thus, it is important to study their capacity to learn flower traits allowing for successful foraging and pollination events, thereby permitting us a better understanding of their role in plant-pollinator interactions.

Individual recognition is associated with holistic face processing in Polistes paper wasps in a species-specific way

Most recognition is based on identifying features, but specialization for face recognition in primates relies on a different mechanism, termed 'holistic processing' where facial features are bound together into a gestalt which is more than the sum of its parts. Here, we test whether individual face recognition in paper wasps also involved holistic processing using a modification of the classic part-whole test in two related paper wasp species: Polistes fuscatus, which use facial patterns to individually identify conspecifics, and Polistes dominula, which lacks individual recognition. We show that P. fuscatus use holistic processing to discriminate between P. fuscatus face images but not P. dominula face images. By contrast, P. dominula do not rely on holistic processing to discriminate between conspecific or heterospecific face images. Therefore, P. fuscatus wasps have evolved holistic face processing, but this ability is highly specific and shaped by species-specific and stimulus-specific selective pressures. Convergence towards holistic face processing in distant taxa (primates, wasps) as well as divergence among closely related taxa with different recognition behaviour (P. dominula, P. fuscatus) suggests that holistic processing may be a universal adaptive strategy to facilitate expertise in face recognition.

Functional involvement of subcortical structures in global-local processing

The present study examined the involvement of subcortical structures in the processing of global and local information. To this end, we used a stereoscope to present hierarchical stimuli (global shapes composed of local elements) in a dichoptic or a monocular fashion, such that global and local information was either presented to the same eye (same-eye condition) or segregated between the eyes (different-eyes condition). In Experiment 1, the typical global advantage and global-to-local interference were observed for the same-eye presentation condition. On the other hand, no indication of a global advantage or of global-to-local interference emerged in the different-eyes presentation condition. In Experiment 2 we replicated these results, ruling out a possible alternative explanation that the pattern of results observed for the different-eyes presentation condition resulted merely from segregation of the stimulus between the eyes. Rather, the experiment demonstrated that the global-to-local interference was eliminated only when global and local information was segregated between the eyes. Taken together, these findings suggest that processing the global aspect of hierarchical stimuli involves subcortical regions indexed by monocular portions of the visual system.

Different mechanisms underlie implicit visual statistical learning in honey bees and humans

The ability of developing complex internal representations of the environment is considered a crucial antecedent to the emergence of humans' higher cognitive functions. Yet it is an open question whether there is any fundamental difference in how humans and other good visual learner species naturally encode aspects of novel visual scenes. Using the same modified visual statistical learning paradigm and multielement stimuli, we investigated how human adults and honey bees (Apis mellifera) encode spontaneously, without dedicated training, various statistical properties of novel visual scenes. We found that, similarly to humans, honey bees automatically develop a complex internal representation of their visual environment that evolves with accumulation of new evidence even without a targeted reinforcement. In particular, with more experience, they shift from being sensitive to statistics of only elemental features of the scenes to relying on co-occurrence frequencies of elements while losing their sensitivity to elemental frequencies, but they never encode automatically the predictivity of elements. In contrast, humans involuntarily develop an internal representation that includes single-element and co-occurrence statistics, as well as information about the predictivity between elements. Importantly, capturing human visual learning results requires a probabilistic chunk-learning model, whereas a simple fragment-based memory-trace model that counts occurrence summary statistics is sufficient to replicate honey bees' learning behavior. Thus, humans' sophisticated encoding of sensory stimuli that provides intrinsic sensitivity to predictive information might be one of the fundamental prerequisites of developing higher cognitive abilities.

How the forest interacts with the trees: Multiscale shape integration explains global and local processing

Hierarchical stimuli have been widely used to study global and local processing. Two classic phenomena have been observed using these stimuli: the global advantage effect (we identify the global shape faster) and an interference effect (we identify shape slower when the global and local shapes are different). Because these phenomena have been observed during shape categorization tasks, it is unclear whether they reflect the categorical judgment or the underlying shape representation. Understanding the underlying shape representation is also critical because both global and local processing are modulated by stimulus properties. We performed two experiments to investigate these issues. In Experiment 1, we show that these phenomena can be observed in a same-different task, and that participants show systematic variation in response times across image pairs. We show that the response times to any pair of images can be accurately predicted using two factors: their dissimilarity and their distinctiveness relative to other images. In Experiment 2, we show that these phenomena can also be observed in a visual search task where participant did not have to make any categorical shape judgments. Here too, participants showed highly systematic variations in response time that could be explained as a linear sum of shape comparisons across global and local scales. Finally, the dissimilarity and distinctiveness factors estimated from the same-different task were systematically related to the search dissimilarities observed during visual search. In sum, our results show that global and local processing phenomena are properties of a systematic shape representation governed by simple rules.

The Role of Landscapes and Landmarks in Bee Navigation: A Review

The ability of animals to explore landmarks in their environment is essential to their fitness. Landmarks are widely recognized to play a key role in navigation by providing information in multiple sensory modalities. However, what is a landmark? We propose that animals use a hierarchy of information based upon its utility and salience when an animal is in a given motivational state. Focusing on honeybees, we suggest that foragers choose landmarks based upon their relative uniqueness, conspicuousness, stability, and context. We also propose that it is useful to distinguish between landmarks that provide sensory input that changes ("near") or does not change ("far") as the receiver uses these landmarks to navigate. However, we recognize that this distinction occurs on a continuum and is not a clear-cut dichotomy. We review the rich literature on landmarks, focusing on recent studies that have illuminated our understanding of the kinds of information that bees use, how they use it, potential mechanisms, and future research directions.

Surpassing the subitizing threshold: appetitive–aversive conditioning improves discrimination of numerosities in honeybees

Animals including humans, fish and honeybees have demonstrated a quantity discrimination threshold at four objects, often known as subitizing elements. Discrimination between numerosities at or above the subitizing range is considered a complex capacity. In the current study, we trained and tested two groups of bees on their ability to differentiate between quantities (4 versus 5 through to 4 versus 8) when trained with different conditioning procedures. Bees trained with appetitive (reward) differential conditioning demonstrated no significant learning of this task, and limited discrimination above the subitizing range. In contrast, bees trained using appetitive–aversive (reward–aversion) differential conditioning demonstrated significant learning and subsequent discrimination of all tested comparisons from 4 versus 5 to 4 versus 8. Our results show conditioning procedure is vital to performance on numerically challenging tasks, and may inform future research on numerical abilities in other animals.

Signal or cue: the role of structural colors in flower pollination

Angle dependent colors, such as iridescence, are produced by structures present on flower petals changing their visual appearance. These colors have been proposed to act as signals for plant-insect communication. However, there is a paucity of behavioral data to allow for interpretations of how to classify these colors either as a signal or a cue when considering the natural conditions under which pollination occurs. We sampled flowers from 6 plant species across various viewpoints looking for changes in the visual appearance of the petals. Spectral characteristics were measured with different instruments to simulate both the spectral and spatial characteristics of honeybee's vision. We show the presence of color patches produced by angle dependent effects on the petals and the calyx of various species; however, the appearance of the angle dependent color patches significantly varies with viewpoint and would only be resolved by the insect eye at close distances. Behavior experiments with honeybees revealed that pollinators did not use angle dependent colors to drive behavior when presented with novel flower presentations. Results show that angle dependent colors do not comply with the requirements of a signal for plant-pollinator communication since the information transmitted by these colors would be unreliable for potential, free-flying pollination vectors. We thus classify angle dependent colors produced by micro- and ultra-structures as being a cue (a feature which has not evolved for communication), and observe no evidence supporting claims of these angle dependent colors having evolved as visual signal.

Honeybees use absolute rather than relative numerosity in number discrimination

Various vertebrate species use relative numerosity judgements in comparative assessments of quantities for which they use larger/smaller relationships rather than absolute number. The numerical ability of honeybees shares basic properties with that of vertebrates but their use of absolute or relative numerosity has not been explored. We trained free-flying bees to choose variable images containing three dots; one group ('larger') was trained to discriminate 3 from 2, while another group ('smaller') was trained to discriminate 3 from 4. In both cases, numbers were kept constant but stimulus characteristics and position were varied from trial to trial. Bees were then tested with novel stimuli displaying the previously trained numerosity (3) versus a novel numerosity (4 for 'larger' and 2 for 'smaller'). Both groups preferred the three-item stimulus, consistent with absolute numerosity. They also exhibited ratio-dependent discrimination of numbers, a property shared by vertebrates, as performance after 2 versus 3 was better than after 3 versus 4 training. Thus, bees differ from vertebrates in their use of absolute rather than of relative numerosity but they also have some numeric properties in common.

Numerical cognition in honeybees enables addition and subtraction

Many animals understand numbers at a basic level for use in essential tasks such as foraging, shoaling, and resource management. However, complex arithmetic operations, such as addition and subtraction, using symbols and/or labeling have only been demonstrated in a limited number of nonhuman vertebrates. We show that honeybees, with a miniature brain, can learn to use blue and yellow as symbolic representations for addition or subtraction. In a free-flying environment, individual bees used this information to solve unfamiliar problems involving adding or subtracting one element from a group of elements. This display of numerosity requires bees to acquire long-term rules and use short-term working memory. Given that honeybees and humans are separated by over 400 million years of evolution, our findings suggest that advanced numerical cognition may be more accessible to nonhuman animals than previously suspected.

Honeybees prefer novel insect-pollinated flower shapes over bird-pollinated flower shapes

Plant–pollinator interactions have a fundamental influence on flower evolution. Flower color signals are frequently tuned to the visual capabilities of important pollinators such as either bees or birds, but far less is known about whether flower shape influences the choices of pollinators. We tested European honeybee Apis mellifera preferences using novel achromatic (gray-scale) images of 12 insect-pollinated and 12 bird-pollinated native Australian flowers in Germany; thus, avoiding influences of color, odor, or prior experience. Independent bees were tested with a number of parameterized images specifically designed to assess preferences for size, shape, brightness, or the number of flower-like shapes present in an image. We show that honeybees have a preference for visiting images of insect-pollinated flowers and such a preference is most-likely mediated by holistic information rather than by individual image parameters. Our results indicate angiosperms have evolved flower shapes which influence the choice behavior of important pollinators, and thus suggest spatial achromatic flower properties are an important part of visual signaling for plant–pollinator interactions.

Does Holistic Processing Require a Large Brain? Insights From Honeybees and Wasps in Fine Visual Recognition Tasks

The expertise of humans for recognizing faces is largely based on holistic processing mechanism, a sophisticated cognitive process that develops with visual experience. The various visual features of a face are thus glued together and treated by the brain as a unique stimulus, facilitating robust recognition. Holistic processing is known to facilitate fine discrimination of highly similar visual stimuli, and involves specialized brain areas in humans and other primates. Although holistic processing is most typically employed with face stimuli, subjects can also learn to apply similar image analysis mechanisms when gaining expertise in discriminating novel visual objects, like becoming experts in recognizing birds or cars. Here, we ask if holistic processing with expertise might be a mechanism employed by the comparatively miniature brains of insects. We thus test whether honeybees (Apis mellifera) and/or wasps (Vespula vulgaris) can use holistic-like processing with experience to recognize images of human faces, or Navon-like parameterized-stimuli. These insect species are excellent visual learners and have previously shown ability to discriminate human face stimuli using configural type processing. Freely flying bees and wasps were consequently confronted with classical tests for holistic processing, the part-whole effect and the composite-face effect. Both species could learn similar faces from a standard face recognition test used for humans, and their performance in transfer tests was consistent with holistic processing as defined for studies on humans. Tests with parameterized stimuli also revealed a capacity of honeybees, but not wasps, to process complex visual information in a holistic way, suggesting that such sophisticated visual processing may be far more spread within the animal kingdom than previously thought, although may depend on ecological constraints.

Perception of contextual size illusions by honeybees in restricted and unrestricted viewing conditions

How different visual systems process images and make perceptual errors can inform us about cognitive and visual processes. One of the strongest geometric errors in perception is a misperception of size depending on the size of surrounding objects, known as the Ebbinghaus or Titchener illusion. The ability to perceive the Ebbinghaus illusion appears to vary dramatically among vertebrate species, and even populations, but this may depend on whether the viewing distance is restricted. We tested whether honeybees perceive contextual size illusions, and whether errors in perception of size differed under restricted and unrestricted viewing conditions. When the viewing distance was unrestricted, there was an effect of context on size perception and thus, similar to humans, honeybees perceived contrast size illusions. However, when the viewing distance was restricted, bees were able to judge absolute size accurately and did not succumb to visual illusions, despite differing contextual information. Our results show that accurate size perception depends on viewing conditions, and thus may explain the wide variation in previously reported findings across species. These results provide insight into the evolution of visual mechanisms across vertebrate and invertebrate taxa, and suggest convergent evolution of a visual processing solution.

Innate colour preference, individual learning and memory retention in the ant Camponotus blandus

Ants are a well-characterized insect model for the study of visual learning and orientation, but the extent to which colour vision is involved in these tasks remains unknown. We investigated the colour preference, learning and memory retention of Camponotus blandus foragers under controlled laboratory conditions. Our results show that C. blandus foragers exhibit a strong innate preference for ultraviolet (UV, 365 nm) over blue (450 nm) and green (528 nm) wavelengths. The ants can learn to discriminate 365 nm from either 528 nm or 450 nm, independent of intensity changes. However, they fail to discriminate between 450 nm and 528 nm. Modelling of putative colour spaces involving different numbers of photoreceptor types revealed that colour discrimination performance of individual ants is best explained by dichromacy, comprising a short-wavelength (UV) receptor with peak sensitivity at about 360 nm, and a long-wavelength receptor with peak sensitivity between 470 nm and 560 nm. Foragers trained to discriminate blue or green from UV light are able to retain the learned colour information in an early mid-term (e-MTM), late mid-term (l-MTM), early long-term (e-LTM) and late long-term (l-LTM) memory from where it can be retrieved after 1 h, 12 h, 24 h, 3 days and 7 days after training, indicating that colour learning may induce different memory phases in ants. Overall, our results show that ants can use chromatic information in a way that should promote efficient foraging in complex natural environments.

Attention-like processes in insects

Attention is fundamentally important for sensory systems to focus on behaviourally relevant stimuli. It has therefore been an important field of study in human psychology and neuroscience. Primates, however, are not the only animals that might benefit from attention-like processes. Other animals, including insects, also have to use their senses and select one among many stimuli to forage, avoid predators and find mates. They have evolved different mechanisms to reduce the information processed by their brains to focus on only relevant stimuli. What are the mechanisms used by insects to selectively attend to visual and auditory stimuli? Do these attention-like mechanisms achieve the same functions as they do in primates? To investigate these questions, I use an established framework for investigating attention in non-human animals that proposes four fundamental components of attention: salience filters, competitive selection, top-down sensitivity control and working memory. I discuss evidence for each of these component processes in insects and compare the characteristics of these processes in insects to what we know from primates. Finally, I highlight important outstanding questions about insect attention that need to be addressed for us to understand the differences and similarities between vertebrate and insect attention.

Visual acuity of the honey bee retina and the limits for feature detection

Visual abilities of the honey bee have been studied for more than 100 years, recently revealing unexpectedly sophisticated cognitive skills rivalling those of vertebrates. However, the physiological limits of the honey bee eye have been largely unaddressed and only studied in an unnatural, dark state. Using a bright display and intracellular recordings, we here systematically investigated the angular sensitivity across the light adapted eye of honey bee foragers. Angular sensitivity is a measure of photoreceptor receptive field size and thus small values indicate higher visual acuity. Our recordings reveal a fronto-ventral acute zone in which angular sensitivity falls below 1.9°, some 30% smaller than previously reported. By measuring receptor noise and responses to moving dark objects, we also obtained direct measures of the smallest features detectable by the retina. In the frontal eye, single photoreceptors respond to objects as small as 0.6° × 0.6°, with >99% reliability. This indicates that honey bee foragers possess significantly better resolution than previously reported or estimated behaviourally, and commonly assumed in modelling of bee acuity.

Neuropeptides as Regulators of Behavior in Insects

Neuropeptides are by far the largest and most diverse group of signaling molecules in multicellular organisms. They are ancient molecules important in regulating a multitude of processes. Their small proteinaceous character allowed them to evolve and radiate quickly into numerous different molecules. On average, hundreds of distinct neuropeptides are present in animals, sometimes with unique classes that do not occur in distantly related species. Acting as neurotransmitters, neuromodulators, hormones, or growth factors, they are extremely diverse and are involved in controlling growth, development, ecdysis, digestion, diuresis, and many more physiological processes. Neuropeptides are also crucial in regulating myriad behavioral actions associated with feeding, courtship, sleep, learning and memory, stress, addiction, and social interactions. In general, behavior ensures that an organism can survive in its environment and is defined as any action that can change an organism's relationship to its surroundings. Even though the mode of action of neuropeptides in insects has been vigorously studied, relatively little is known about most neuropeptides and only a few model insects have been investigated. Here, we provide an overview of the roles neuropeptides play in insect behavior. We conclude that multiple neuropeptides need to work in concert to coordinate certain behaviors. Additionally, most neuropeptides studied to date have more than a single function.

Global/local processing of hierarchical visual stimuli in a conflict-choice task by capuchin monkeys (Sapajus spp.)

In the last two decades, comparative research has addressed the issue of how the global and local levels of structure of visual stimuli are processed by different species, using Navon-type hierarchical figures, i.e. smaller local elements that form larger global configurations. Determining whether or not the variety of procedures adopted to test different species with hierarchical figures are equivalent is of crucial importance to ensure comparability of results. Among non-human species, global/local processing has been extensively studied in tufted capuchin monkeys using matching-to-sample tasks with hierarchical patterns. Local dominance has emerged consistently in these New World primates. In the present study, we assessed capuchins' processing of hierarchical stimuli with a method frequently adopted in studies of global/local processing in non-primate species: the conflict-choice task. Different from the matching-to-sample procedure, this task involved processing local and global information retained in long-term memory. Capuchins were trained to discriminate between consistent hierarchical stimuli (similar global and local shape) and then tested with inconsistent hierarchical stimuli (different global and local shapes). We found that capuchins preferred the hierarchical stimuli featuring the correct local elements rather than those with the correct global configuration. This finding confirms that capuchins' local dominance, typically observed using matching-to-sample procedures, is also expressed as a local preference in the conflict-choice task. Our study adds to the growing body of comparative studies on visual grouping functions by demonstrating that the methods most frequently used in the literature on global/local processing produce analogous results irrespective of extent of the involvement of memory processes.

The answer is blowing in the wind: free-flying honeybees can integrate visual and mechano-sensory inputs for making complex foraging decisions

Bees navigate in complex environments using visual, olfactory and mechano-sensorial cues. In the lowest region of the atmosphere, the wind environment can be highly unsteady and bees employ fine motor-skills to enhance flight control. Recent work reveals sophisticated multi-modal processing of visual and olfactory channels by the bee brain to enhance foraging efficiency, but it currently remains unclear whether wind-induced mechano-sensory inputs are also integrated with visual information to facilitate decision making. Individual honeybees were trained in a linear flight arena with appetitive-aversive differential conditioning to use a context-setting cue of 3 m s^-1 cross-wind direction to enable decisions about either a 'blue' or 'yellow' star stimulus being the correct alternative. Colour stimuli properties were mapped in bee-specific opponent-colour spaces to validate saliency, and to thus enable rapid reverse learning. Bees were able to integrate mechano-sensory and visual information to facilitate decisions that were significantly different to chance expectation after 35 learning trials. An independent group of bees were trained to find a single rewarding colour that was unrelated to the wind direction. In these trials, wind was not used as a context-setting cue and served only as a potential distracter in identifying the relevant rewarding visual stimuli. Comparison between respective groups shows that bees can learn to integrate visual and mechano-sensory information in a non-elemental fashion, revealing an unsuspected level of sensory processing in honeybees, and adding to the growing body of knowledge on the capacity of insect brains to use multi-modal sensory inputs in mediating foraging behaviour.

Functional Significance of Labellum Pattern Variation in a Sexually Deceptive Orchid (Ophrys heldreichii): Evidence of Individual Signature Learning Effects

Mimicking female insects to attract male pollinators is an important strategy in sexually deceptive orchids of the genus Ophrys, and some species possess flowers with conspicuous labellum patterns. The function of the variation of the patterns remains unresolved, with suggestions that these enhance pollinator communication. We investigated the possible function of the labellum pattern in Ophrys heldreichii, an orchid species in which the conspicuous and complex labellum pattern contrasts with a dark background. The orchid is pollinated exclusively by males of the solitary bee, Eucera berlandi. Comparisons of labellum patterns revealed that patterns within inflorescences are more similar than those of other conspecific plants. Field observations showed that the males approach at a great speed and directly land on flowers, but after an unsuccessful copulation attempt, bees hover close and visually scan the labellum pattern for up to a minute. Learning experiments conducted with honeybees as an accessible model of bee vision demonstrated that labellum patterns of different plants can be reliably learnt; in contrast, patterns of flowers from the same inflorescence could not be discriminated. These results support the hypothesis that variable labellum patterns in O. heldreichii are involved in flower-pollinator communication which would likely help these plants to avoid geitonogamy.