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Modelling Multi-modal Learning in a Hawkmoth
Abstract
The moth Macroglossum stellatarum can learn the colour and sometimes the odour of a rewarding food source. We present data from 20 different experiments with
different combinations of blue and yellow artificial flowers and the two odours honeysuckle and lavender. The experiments
show that learning about the odours depends on the colour used. By training on different colour-odour combinations and testing
on others, it becomes possible to investigate the exact relation between the two modalities during learning. Three computational
models were tested in the same experimental situations as the real moths and their predictions were compared to the experimental
data. The average error over all experiments as well as the largest deviation from the experimental data were calculated.
Neither the Rescorla-Wagner model or a learning model with independent learning for each stimulus component were able to explain
the experimental data. We present the new categorisation model, which assumes that the moth learns a template for the sensory
attributes of the rewarding stimulus. This model produces behaviour that closely matches that of the real moth in all 20 experiments.
... Associative learning theories predict that stimuli with a higher salience (conspicuousness) are more easily associated with rewards despite equal reinforcements, i.e. the same reward qualities (Rescorla and Wagner 1972). The salience of stimuli may be altered either by the concentration of individual compounds that contribute to a stimulus or by combining compounds of one or more modalities (Pelz et al. 1997; Balkenius et al. 2006; Chow and Frye 2008). In this study, we evaluated how the visual and olfactory salience of various uniand multimodal stimuli (naturally occurring floral volatiles and pigments) affects initial responses and learning success of bumblebees (Bombus terrestris) to address the following hypotheses: (a) The stimuli differ in their olfactory and visual salience and also associative strength, i.e. the learning success of bumblebees varies across stimuli, (b) the olfactory and visual salience of a compound stimulus (i.e. ...
Visual and olfactory cues are the first interface between flowers and their visitors and are adaptations to facilitate successful pollination. Initial responses to and associative learning of multimodal cues by flower visitors are based on the perception of colours and volatiles. In this study, we tested how visual, olfactory and multimodal stimuli affect the behaviour of bumblebees (Bombus terrestris) and correlated the properties of 28 stimuli in relation to the insects’ sensory equipment to these behaviours. Initial responses and associative learning were recorded using a radio frequency identification system, tracking the visitation sequences of individual bumblebees to artificial flowers treated with naturally occurring pigments and/or volatiles. The salience of the stimuli was evaluated as the colour contrast to the background and as electroantennogram responses. The main finding was that both initial responses and learning performance were positively correlated to the salience of the stimuli, suggesting that salience is a key feature of flower cues in the interactions with insects. The salience of compound stimuli consisting of two or more pigments and/or volatiles was largely additively determined by the saliences of individual compounds. Potentially, the valence of the stimuli may interfere with the positive relationship between salience and behaviour, which is indicated by our results, too. The salience of multimodal cues depends on the species-specific equipment of visual and olfactory receptors and thus enables flowers to be advertising for some but rather inconspicuous for other flower visitors.
... Note that this rule, unlike the previous one, can also lead to conditioned inhibition (negative values): for example, if B has initial value zero, and a positive US value predicted by A does not occur after presentation of AB, B will be decreased below zero. Balkenius, Kelber, and Balkenius (2006), modelling multimodal learning in hawkmoths, suggest an alternative rule for learning, based on the concept that the animal is attempting to form a template for the reinforced CS, whenever the US occurs, by increasing the value of elements present and decreasing the value of elements not present. It assumes: ...
In behavioral experiments, the hawkmoth Deilephila elpenor can learn both the color and the position of artificial flowers. When very similar colors are used, moths select the correct color during the first test on a given day, thus using a stimulus strategy, but after repeated rewards, they switch to a place strategy and choose the flower in the position where they received the reward. When dissimilar colors are used, the moths continue to select flowers based on color and ignore position. We show how a computational model can reproduce the behavior in the experimental situation. The aim of the model is to investigate which learning and behavior selection strategies are necessary to reproduce the behavior observed in the experiment. The model is based on behavioral data and the sensitivities of the moth photoreceptors. The model consists of a number of interacting behavior systems that are triggered by specific stimuli and control specific behaviors. The ability of the moth to learn the colors of different flowers and the adaptive processes involved in the choice between stimulus-approach and place-approach strategies are reproduced very accurately by the model. The model has implications both for further studies of the ecology of the animal and for robotic systems.
It is common for a smell or a sound to trigger a vivid recollection of an associated event in the past, even if it involves a different sensory modality and the episode occurred a long time ago
1. Honeybees Apis mellifera ligustica were trained to work on a patch with artificial rewarding and non-rewarding flowers, coupled to an air extractor. The perceptual colour distance between the rewarding and the non-rewarding flowers was varied and the flower choice and the repellent scent-marking behaviour of the bees were recorded. 2. The discrimination between rewarding and non-rewarding flowers depended on their colour distance, improving with a greater colour difference. This task was guided thus visually and was not affected by activating the air extractor. 3. The scent-marking activity was only observable when the colour information of both groups of flowers was the same or very similar. This thus represents the first reported case of a modulation of an olfactory activity through the visual input provided by colour distances. When the air extractor was activated, rejections associated with the scent-marking behaviour disappeared, thus confirming the olfactory nature of this behaviour. 4. Honeybees are thus capable of using one or more sensory cues to enhance their foraging efficiency, according to the environmental situation. This great plasticity allows them to attain an enhanced efficiency while foraging. 5. We successfully applied the model of colour choice behaviour of the honeybee. Since the original theory was developed for Apis mellifera carnica, this work also constitutes the first attempt to describe the behaviour of the honeybee race, Apis mellifera ligustica, using the postulated model, and reaffirms thus its generality.
Foraging honeybees were trained in a concurrent blocking design with a compound stimulus (AX) reinforced and one of its components
(A) either reinforced for a blocking group or nonreinforced for a control group. In Experiment 1, a compound of two colors
was used; in Experiment 2, a compound of two odors was used; in Experiment 3, a color-position compound, with position defined
in terms of proximity to a distinctive visual landmark, was used; and, in Experiment 4, an odor-position compound was used.
In each of the first three experiments, the blocking group responded less than did the control group in a subsequent test
with X; in the fourth experiment, the two groups did not differ. The results are in accord with expectations based on those
of previous experiments with honeybees in which the independence assumption was found to hold for intermodal compounds but
not for intramodal compounds.
1.
Under natural day light conditions (700 Lx) individual bees were offered horizontaly situated spectral lights as food signals marking a two molar sucrose solution. The radiation density of the colours corresponds approximately to that of flowers under a hazy sun (Table 3).
2.
A method of quantitatively investigating learning of spectral colours in bees is described. After bees were introduced to the apparatus (=pre-training) the spontanious preference for one of two lights of different wave-length, but equal number of quants, was tested. Following the pre-training the learning process of one of these two lights (λ
+) is illustrated by curves (Figs. 5 and 6).
3.
The ratio of radiation (in quants) of the two lights so that they are equally spontaneously chosen by bees depends on the kind of pre-training. The learning of the colours, however, is not dependent on pre-training.
4.
Different spectral colours are learned at different speeds and with different rates of success. Already after the first trail violet (413, 428 nm) is chosen with a certainity of more than 85%, in contrast the other colours with a certainity of only 60–67%. Bees are slowest to learn blue-green (494 nm) (Figs. 8 and 9).
5.
External factores (temperature, sunshine, season, nectar-concurrence of neighborhood) do not markedly influence the learning process (Fig. 7).
6.
The alternative colour (λ
−) offered in the test situation do not effect the learning process, unless its hue is similar to that of the positive colour (λ
+) for bees. (Figs. 13–17).
7.
From a threshold radiation intensity which depends on the wave-length rate of learning increases rapidly reaching a plateau demonstrating that within a certain range learning is independent of radiation density (Figs. 18–22).
8.
The experimental data are compared with results on colour perception in bees and the significance of colour learning for the orientation to natural colour marks is discussed.
Flower-naive honeybees Apis mellifera L. flying in an enclosure were tested for their colour preferences. Bees were rewarded once on an achromatic (grey, aluminium or hardboard), or on a chromatic (ultraviolet) disk. Since naive bees never alighted on colour stimuli alone, a scent was given in combination with colour. Their landings on twelve colour stimuli were recorded. Results after one reward (first test) were analysed separately from those obtained after few rewards (late tests).1)
After pre-training to achromatic signals, bees preferred, in the first test, bee-uv-blue and bee-green colours. With increasing experience, the original preference pattern persisted but the choice of bee-blue and bee-green colours increased.
2)
Neither colour distance of the test stimuli to the background or to the pre-training signal, nor their intensity, nor their green contrast, accounted for the colour choice of bees. Choices reflected innate preferences and were only associated with stimulus hue.
3)
Bees learned very quickly the pre-trained chromatic stimulus, the original colour preferences being thus erased.
4)
Colour preferences were strongly correlated with flower colour and its associated nectar reward, as measured in 154 flower species.
5)
Colour preferences also resemble the wavelength dependence of colour learning demonstrated in experienced bees.
Previous experiments have shown that honeybees trained with colored targets baited with 5- versus 20-µl drops of sucrose solution
fail to develop a preference for the 20-µl color when the location of the drop on each target is marked by a white dot (dot-color
overshadowing) but that discrimination is not impaired by dots when the targets differ in odor rather than in color. In Experiments
1–3, dot-color overshadowing failed to appear with differences in concentration rather than amount of sucrose (50% vs. 20%
or 0%), but it did appear in Experiments 4 and 5 with a difference in probability of reward (consistent vs. partial). Experiment
6 showed no dot-odor overshadowing with a difference in probability of reward. The results are not generally predictable from
the Rescorla-Wagner principle of shared associative strength, but point instead (in conjunction with those of earlier experiments)
to competition for visual attention.
Six experiments with color-odor compounds failed to produce convincing evidence of blocking in honeybees even when the possibility
of masking by within-compound association could be discounted. The parsimonious assumption that the components of a compound
stimulus gain and lose associative strength independently with reinforcement and nonreinforcement of the compounds (which
the experiments were designed to challenge) remains tenable for color-odor compounds, although perhaps not for intramodal
compounds.
The importance of innate preferences and learned associations in choice of flower colours were investigated for the pipevine swallowtail butterfly,Battus philenor(Papilionidae). Naive butterflies showed innate colour preferences for yellow and, to a lesser extent, blue and purple. Apart from their innate preferences, they were able to learn within 10 flower visits to associate floral colour with the presence of nectar rewards in yellow or magentaLantana camara(Verbenaceae) flowers. Continued experience resulted in greater discrimination in favour of the rewarding colour. Most individuals readily shifted their foraging behaviour when the colour of the rewarding flower was changed. A capacity for rapid and flexible associative learning presumably allows butterflies to adjust their foraging efforts in response to floral rewards that vary over space or time. 1997 The Association for the Study of Animal Behaviour
Food-deceptive flowers are pollinated by animals that expect a reward but are cheated. Such plants profit from their similarity to rewarding plants and should develop signals that hinder discrimination. We use artificial rewarding model flowers and nonrewarding mimicking flowers that present similar visual cues. We test how additional scent cues change flower choice of the mimic by bumble bees ( Bombus terrestris ) in two situations: (1) both flower types are simultaneously present and can be compared by the pollinator, and (2) both flower types are encountered successively in the absence of each other. We find that in situation 1, discrimination learning is greater if scents are used as cues for identifying the mimic, whether the mimic has a different scent or if it is scentless while the model is scented. In situation 2, a generalization task, a scented mimic is avoided faster than a scentless one. Discrimination of the mimic is poorest if it has the same scent as the model, thus demonstrating a potential for scent mimicry, which has not yet been proved to exist among differently rewarding flowers. Thus, the best strategy for a mimic would be to have the same scent as the model, but this strategy may not be used due to evolutionary constraints. Alternatively, if there are several potential models, then having no scent would be a better strategy than mimicking just one of the models. In situation 1 flower discrimination by color cues is enhanced in the mere presence of scent, compared to unscented controls, even if the scent does not provide a distinguishable cue itself. The results indicate that the presence of scent may enhance color discrimination by improving attention towards visual cues and/or that combined color/odor cues may lead to better memory formation and retrieval.
The diurnal hawkmoth Macroglossum stellatarum is known to feed from a variety of flower species of almost all colours, forms and sizes. A newly eclosed imago, however, has to find its first flower by means of an innate flower template. This study investigates which visual flower features are represented in this template and their relative importance. Newly eclosed imagines were tested for their innate preferences, using artificial flowers made out of coloured paper or projected onto a screen through interference filters. The moths were found to have a strong preference for 440 nm and a weaker preference for 540 nm. The attractiveness of a colour increases with light intensity. The background colour, as well as the spectral composition of the ambient illumination, influences the choice behaviour. Blue paper disks against a yellowish background are chosen much more often than the same disks against a bluish background. Similarly, under ultraviolet-rich illumination, the preference for 540 nm is much more pronounced than under yellowish illumination. Disks of approximately 32 mm in diameter are preferred to smaller and larger ones, and a sectored pattern is more attractive than a ring pattern. Pattern preferences are less pronounced with coloured than with black-and-white patterns. Tests using combinations of two parameters reveal that size is more important than colour and that colour is more important than pattern.
The traditional approach to the study of selective attention in animal discrimination learning has been to ask if animals are capable of the central selective processing of stimuli, such that certain aspects of the discriminative stimuli are partially or wholly ignored while their relationships to each other, or other relevant stimuli, are processed. A notable characteristic of this research has been that procedures involve the acquisition of discriminations, and the issue of concern is whether learning is selectively determined by the stimulus dimension defined by the discriminative stimuli. Although there is support for this kind of selective attention, in many cases, simpler nonattentional accounts are sufficient to explain the results. An alternative approach involves procedures more similar to those used in human information-processing research. When selective attention is studied in humans, it generally involves the steady state performance of tasks for which there is limited time allowed for stimulus input and a relatively large amount of relevant information to be processed; thus, attention must be selective or divided. When this approach is applied to animals and alternative accounts have been ruled out, stronger evidence for selective or divided attention in animals has been found. Similar processes are thought to be involved when animals search more natural environments for targets. Finally, an attempt is made to distinguish these top-down attentional processes from more automatic preattentional processes that have been studied in humans and other animals.
Previous findings of intramodal but not of intermodal blocking in foraging honeybees prompted a new series of experiments with colours, odours, a proximal visual landmark, and a localized geomagnetic anomaly as stimuli. In Experiments 1-2, the landmark was blocked by both colour and odour. In Experiments 3-6, the anomaly was blocked by both colour and odour, but the anomaly failed to block either colour or odour. In Experiments 7-8, the anomaly failed again to block either colour or odour even though it could be shown to develop substantial associative strength in the course of the training. The several instances of intermodal blocking bring the results for honeybees into closer agreement than before with the results for vertebrates. The failures of blocking seem understandable in terms of the relative salience of the stimuli employed without reference to modal relationships. An attentional interpretation is suggested.
Floral volatiles play a major role in plant–insect communication. We examined the influence of two volatiles, phenylacetaldehyde andα -pinene, on the innate and learnt foraging behaviour of the moth Helicoverpa armigera. In dual-choice wind tunnel tests, adult moths flew upwind towards both volatiles, with a preference for phenylacetaldehyde. When exposure to either of these volatiles was paired with a feeding stimulus (sucrose), all moths preferred the learnt odour in the preference test. This change in preference was not seen when moths were exposed to the odour without a feeding stimulus. The learnt preference for the odour was reduced when moths were left unfed for 24 h before the preference test.
We tested whether moths could discriminate between flowers that differed in a single volatile component. Moths were trained to feed on flowers that were odour-enhanced using either phenylacetaldehyde or α-pinene. Choice tests were then carried out in an outdoor flight cage, using flowers enhanced with either volatile. Moths showed a significant preference for the flower type on which they were trained. Moths that were conditioned on flowers that were not odour-enhanced showed no preference for either of the odour-enhanced flower types. The results imply that moths may be discriminating among odour profiles of individual flowers from the same species. We discuss this behaviour within the context of nectar foraging in moths and odour signalling by flowering plants.
Diurnal and nocturnal hawkmoths have been shown to use colour vision for flower discrimination. Here, we present evidence that the nocturnal hawkmoth Deilephila elpenor and the diurnal hawkmoth Macroglossum stellatarum also have colour constancy. Colour constancy was shown in D. elpenor in two multiple-choice experiments with five different bluish colour patches under white and blue illumination and with five yellowish colour patches under white, blue and yellow illumination. The mechanism underlying colour constancy in both species was investigated in two dual-choice experiments. The choice behaviour is consistent with the use of the von Kries coefficient law. Although the moths have colour constancy, they react to the colour of the illumination. They make fewer choices when tested under the changed illumination, where they never receive a reward, compared with the training illumination. Even if colour constancy can be explained by a von Kries adaptation mechanism, the fact that the animals discriminate between different illuminations indicates that some additional process must be involved.
Over a century ago workers such as J. Lubbock and K. von Frisch developed behavioural criteria for establishing that non-human animals see colour. Many animals in most phyla have since then been shown to have colour vision. Colour is used for specific behaviours, such as phototaxis and object recognition, while other behaviours such as motion detection are colour blind. Having established the existence of colour vision, research focussed on the question of how many spectral types of photoreceptors are involved. Recently, data on photoreceptor spectral sensitivities have been combined with behavioural experiments and physiological models to study systematically the next logical question: 'what neural interactions underlie colour vision?' This review gives an overview of the methods used to study animal colour vision, and discusses how quantitative modelling can suggest how photoreceptor signals are combined and compared to allow for the discrimination of biologically relevant stimuli.
Important breakthroughs have recently been made in our understanding of the cognitive and sensory abilities of pollinators: how pollinators perceive, memorise and react to floral signals and rewards; how they work flowers, move among inflorescences and transport pollen. These new findings have obvious implications for the evolution of floral display and diversity, but most existing publications are scattered across a wide range of journals in very different research traditions. This book brings together for the first time outstanding scholars from many different fields of pollination biology, integrating the work of neuroethologists and evolutionary ecologists to present a multi-disciplinary approach. Aimed at graduates and researchers of behavioural and pollination ecology, plant evolutionary biology and neuroethology, it will also be a useful source of information for anyone interested in a modern view of cognitive and sensory ecology, pollination and floral evolution.
The Nobel Prize-winning scientist offers a precise, full, and accessible exposition of his landmark work in experimental psychology. Pavlov details the technical means by which he established experiments and controls, the experiments, observations on formation of conditioned reflexes, external and internal reflex inhibitions, the function of cerebral hemispheres and cortex, and more. 18 figures.
To better understand the biological role of floral scents for
butterflies, electrophysiological responses to floral scents were
investigated using combined gas chromatography and electroantennographic
detection (GC-EAD). The antennal responses of three butterfly species,
Aglais urticae L. (Nymphalidae), Inachis io L. (Nymphalidae), and
Gonepteryx rhamni L. (Pieridae) to floral scent compounds from both
natural and synthetic mixtures were examined. Floral scents were
collected from the butterfly nectar plants Cirsium arvense (L.)
(Asteraceae), and Buddleja davidii Franchet cv. (Loganicaeae) with
dynamic head-space methods on Tenax-GR and eluted with pentane. These
eluates, composed of natural floral scent blends, represent an array of
compounds in their natural state. In the GC-EAD analyses eleven
compounds were identified from C. arvense with the benzenoid compound
phenylacetaldehyde in highest abundance. Seventeen compounds were
identified from B. davidii with the irregular terpene oxoisophorone in
highest abundance. Thirty-nine synthetic floral scent compounds were
mixed in pentane, in equal amounts; about 35 ng were allowed to reach
the antennae. The butterflies showed antennal responses to most of the
floral scent compounds from both natural and synthetic blends except to
the highly volatile monoterpene alkenes. Certain benzenoid compounds
such as phenylacetaldehyde, monoterpenes such as linalool, and irregular
terpenes such as oxoisophorone, were emitted in relatively large amounts
from C. arvense and B. davidii, and elicited the strongest antennal
responses. These compounds also elicited strong antennal responses when
present in the synthetic scent blends. Thus, the butterflies seem to
have many and /or sensitive antennal receptors for these compounds,
which points to their biological importance. Moreover, these compounds
are exclusively of floral scent origin. For B. davidii, which depends
highly on butterflies for pollination, the exclusive floral scent
compounds emitted in high abundance could be the result of an adaptive
pressure to attract butterflies.
For butterflies to be efficient foragers, they need to
be able to recognize rewarding flowers. Flower signals such as colours
and scents assist this recognition process. For plant species to attract
and keep butterflies as pollinators, species-specific floral signals are
crucial. The aim of this study is to investigate foraging responses to
floral scents in three temperate butterfly species, Inachis io L.
(Nymphalidae), Aglais urticae L. (Nymphalidae), and
Gonepteryx rhamni L. (Pieridae), in behavioural choice
bioassays. The butterflies were allowed to choose bet-ween flower models
varying in scent and colour (mauve or green). Flowers or vegetative
parts from the plants Centaurea scabiosa L. (Asteraceae),
Cirsium arvense (L.) (Asteraceae), Knautia arvensis (L.)
(Dipsacaceae), Buddleja davidii Franchet (Loganicaeae), Origanum vulgareL. (Lamiaceae), Achillea millefolium L. (Asteraceae), and
Philadelphus coronarius L. (Hydrangiaceae) were used as scent
sources. All visits to the models — those that included probing and
those that did not — were counted, as was the duration of these
behaviours. Both flower-naive and flower-experienced (conditioned to
sugar-water rewards, the colour mauve, and specific floral scents)
butterflies were tested for their preference for floral versus
vegetative scents, and to floral scent versus colour. The butterflies
were also tested for their ability to switch floral scent preferences in
response to rewards. Flower-naive butterflies demonstrated a preference
for the floral scent of the butterfly-favourable plants C.
arvense and K. arvensis over the floral scent of the non-favourable
plants Achillea millefolium (Asteraceae), and Philadelphus
coronarius cv. (Hydrangiaceae). Most of the butterflies that were
conditioned to floral scents of either C. arvense, K. arvensis,
or B. davidii readily switched theirfloral scent preferences to
the one most recently associated with reward, thus demonstrating that
floral scent constancy is a result from learning. These findings suggest
that these butterflies use floral scent as an important cue signal to
initially identify and subsequently recognize and distinguish among
rewarding plants.
Hymenopterans have long been shown to choose colours by means of the spectral distribution and independently of the intensity
(true colour vision). The same ability has only very recently been proven for two butterfly species. We present evidence for
the existence of true colour vision in the European hummingbird hawkmoth, Macroglossum stellatarum. Moths were trained in dual-choice situations to spectral lights of a rewarding and an unrewarding wavelength. After training,
unrewarded tests were performed during which the intensities of the lights were changed. The results confirm that the species
has three spectral receptor types and uses true colour vision when learning the colour of a food source. If colour vision
is not possible since only one receptor type is receiving input from both stimuli, the moths learn to associate some achromatic
cue correlated to the receptor quantum catch, with the reward. The moths learn spectral cues rapidly and choose correctly
after one to several rewarded visits even when trained to different colours in sequence.
Communication between flowering plants and their pollinators involves innate, learned and deceptive sensory signals. Nocturnal, hawkmoth-pollinated flowers are among the most reflective and strongly scented known, suggesting the potential for multimodal sensory communication with pollinators. We measured the relative importance of these overstated signals, both alone and in combination, to nectar feeding by naı̈ve male hawkmoths, Manduca sexta. In the absence of fragrance, moths hovered and repeatedly passed (in flight) within 1 m above arrays of model paper flowers. The presence of plant odours elicited significantly more hovers and close passes, as well as three additional behaviours: approaches to the paper flowers, approaches to the hidden odour source and nectar feeding. However, approaches to odour sources never resulted in proboscis extension or probing in the absence of a visual target. Nectar feeding increased six-fold when paper and natural flowers were presented in mixed arrays, but moths did not show preferential visits or constancy to either type of flower. Significantly ordered behavioural sequences were observed when both visual and olfactory stimuli were present, but not when fragrance was absent. The largest conditional probabilities indicated a chain of responses beginning with hovering and leading to floral approach and nectar feeding. As single modality cues, both floral fragrance and visual display are innately attractive to male M. sexta, but the combination thereof is required to elicit proboscis extension and feeding.
Stimulus intensity is an important determinant for perception, learning and behaviour. We studied the effects of odorant concentration on classical conditioning involving odorants and odorant-mechanosensory compounds using the proboscis-extension reflex in the honeybee.
Our results show that high concentrations of odorant (a) support better discrimination in a feature-positive task using rewarded odorant-mechanosensory compounds versus unrewarded mechanosensory stimuli, (b) have a stronger capacity to overshadow learning of a simultaneously trained mechanosensory stimulus, and (c) induce better memory consolidation. Furthermore, honeybees were trained discriminatively to two different concentrations of one odorant. Honeybees are not able to solve this task when presented with rewarded low versus unrewarded high concentrations.
Taken together, our results suggest that high concentrations of odorant support stronger associations (are more ‘salient’) than low concentrations. Our results, however, do not indicate that honeybees can treat two different concentrations of one odorant as qualitatively different stimuli. These findings fill a gap in what is known about honeybee olfactory learning and are a first step in relating behaviour to recent advances in the physiological analysis of coding for odorant concentration in honeybees.
We use binary odorant compounds to investigate 'blocking' in honeybees which learn to associate an odorant (A-D) with a sucrose reward as the reinforcer (+). 'Blocking' means that learning about a stimulus B is reduced when trained in compound with a stimulus A that has previously been trained alone. Thus, reinforcement of B in these circumstances is not sufficient to induce learning. Such blocking is a frequently observed phenomenon in vertebrate learning and has also recently been reported in honeybee olfactory learning. To explain blocking, current models of conditioning include cognition-like concepts of attention or expectation which, consequently, seem also to apply to honeybees. Here, we first reproduce a blocking-like effect in an experimental design taken from the literature. We identify two confounding variables in that design and experimentally demonstrate their potential to support a blocking-like effect. After eliminating these confounding variables using a series of different training procedures, the blocking-like effect disappeared. Thus, convincing evidence for blocking in honeybee classical conditioning is at present lacking. This casts doubt on the applicability of cognition-like concepts to honeybees.
Many animals produce and respond to signals made up of multiple components. For example, many avian sexual displays are highly extravagant combinations of visual and acoustic elements, and are described as being 'multicomponent'. One possible reason for the evolution of such complex signals is that they provide more reliable information for receivers. However, receivers also influence signal evolution in another important way, by how they perceive and process signals: signallers will be selected to produce signals that are more easily received. The potential role of receiver psychology in the evolution of multicomponent signals has not previously been considered; in this review I present psychological results that support the notion that two components are better received than one alone. Detection can be improved by producing two components together, thus reducing the reaction time, increasing the probability of detection and lowering the intensity at which detection occurs. Discriminability of multicomponent stimuli is also made easier through better recognition, faster discrimination learning and multidimensional generalization. In addition, multicomponent stimuli also improve associative learning. I show that multicomponency does indeed improve signal reception in receivers, although the benefits of producing components in two sensory modalities (bimodal multicomponent signals) may be larger and more robust than producing them in just one (unimodal multicomponent signals). This highlights the need for consideration of receiver psychology in the evolution of multicomponent signals, and suggests that where signal components do not appear to be informative, they may instead be performing an important psychological function. Copyright 1999 The Association for the Study of Animal Behaviour.
Nectar-feeding animals can use vision and olfaction to find rewarding flowers and different species may give different weight to the two sensory modalities. We have studied how a diurnal or nocturnal lifestyle affects the weight given to vision and olfaction. We tested naïve hawkmoths of two species in a wind tunnel, presenting an odour source and a visual stimulus. Although the two species belong to the same subfamily of sphingids, the Macroglossinae, their behaviour was quite different. The nocturnal Deilephila elpenor responded preferably to the odour while the diurnal Macroglossum stellatarum strongly favoured the visual stimulus. Since a nocturnal lifestyle is ancestral for sphingids, the diurnal species, M. stellatarum, has evolved from nocturnal moths that primarily used olfaction. During bright daylight visual cues may have became more important than odour.
The hummingbird hawkmoth, Macroglossum stellatarum, learns colour fast and reliably. It has earlier been shown to spontaneously feed from odourless artificial flowers. Now, we have studied odour learning. The moths were trained to discriminate feeders of the same colour but marked with different odours. They did not learn to discriminate two natural flower odours when they were presented with the innately preferred colour blue, but they did learn this discrimination combined with yellow or green colours that are less attractive to the moth. The yellow colour could be trained to become as attractive as the innately preferred blue colour and the blue colour could be trained to become less attractive. This is the first proof of odour learning in a diurnal moth. The results show that M. stellatarum can use more than one modality in their foraging behaviour and that the system is plastic. By manipulating the preferences for the different colours, their influence on odour learning could be changed.
Sensory responses to flowers in night-flying moths The pollinaton of flowers by insects
- N B M Brantjes
Data fusion and sensor integration: state-of-the-art 1990s Data Fusion in Robotics and Machine Intelligence
- R C Luo
- M G Kay
Ein vielseitiger Futterspender für anthophile Insekten
- M Pfaff
- A Kelber
- M. Pfaff
Der Farbensinn und Formensinn der Biene
- K Von Frisch
- K. Frisch von
Menzel Colour preferences of flower-naive honeybees
- Giurfa
- Núñez
- R Chittka
Sensory responses to flowers in night-flying moths
- N B M Brantjes
- N.B.M. Brantjes