Lars Chittka

Behavioral flexibility—the ability to adapt behavior in response to changing conditions—is commonly measured using reversal learning tasks, where individuals must inhibit a previously rewarded response and adopt a new one after contingencies change. Despite widespread use, task comparability across species remains unclear. We systematically reviewed 206 empirical studies (2014–2023) spanning eight taxa: invertebrates, fishes, amphibians and reptiles, birds, rodents, non-human primates, humans, and other mammals. We extracted species coverage, sampling, learning and reversal criteria, cue types, and outcome measures, and characterized cross-taxon variation using nonparametric tests, correlation analyses, linear discriminant analyses, and model-based robustness checks. We identify three methodological obstacles. First, research is highly imbalanced, concentrated on humans, birds, and rodents. Most animal diversity remains virtually untested, with under 1% of described species represented in five of the seven non-human taxa. Second, research is taxonomically fragmented: 99% of studies examine only one taxon, limiting direct comparisons. Third, methodological standards diverge dramatically across taxa. Humans consistently face the strictest learning criteria, while other taxa typically use lower thresholds. Mean reversal phases differ more than threefold across taxa: single-reversal designs predominate in amphibians and reptiles, fishes, and invertebrates, whereas multi-reversal protocols are relatively more frequent in humans and non-human primates. Sample sizes, evaluation window lengths, cue types, and outcome measures also show taxon-specific patterns. These systematic design differences complicate cross-taxon comparisons, blurring the line between true cognitive variation and methodological artifacts. Greater methodological coordination and broader taxonomic coverage are needed, and emerging large-scale collaborations offer a promising path forward.

Honeybee comb is unique among animal architectures in its strikingly regular hexagonal cells, yet how this geometry emerges remains debated. Do bees construct perfect hexagons from the outset, or does regularity arise through later adjustments? We examined comb-building dynamics by presenting honeybees ( Apis mellifera ) with wax stimuli that constrained cell placement and angular space. Across three experiments, we tested predictions about how bees distribute the available angular range at cell junctions, shape cell bases, and correct irregularities over time. Initially, cells were uneven, with curved walls and variable angles. When the angular space was restricted to 180°, bees built cells with 90° internal angles; as construction progressed and barriers eroded, angles shifted toward 120°, equalizing the 360° range among three adjoining cells. Similarly, opposed cells formed flat bases orthogonal to side walls (≈90°), contrasting with the pyramidal bases of natural comb. When separate tongues of comb merged, cells at junctions were highly irregular, but subsequent work significantly reduced disparities in wall angles and cell size. These findings reveal that honeycomb cell geometry emerges through a self-organizing process: bees iteratively redistribute space and adjust cell boundaries until equilibrium is achieved. This dynamic optimization explains the iconic hexagonal pattern without invoking complex cognitive strategies.

Bee World: What initially sparked your interest in studying bees?Lars Chittka: As an undergraduate student, during a 1-month practical, we focussed on the pharmacology of associative learning, but ...

Male bees navigate complex tradeoffs between energy acquisition and reproductive signaling, yet their movement strategies remain understudied. Unlike workers that optimize foraging to support the colony, male bumblebees (Bombus terrestris) forage independently to collect nectar and deposit sex pheromones on selected plants. Using high-resolution 3D tracking in an indoor flight cage, we investigated how the spatial arrangement of nectar and scent-marking sites, along with nectar availability, influence male movement patterns. We manipulated the distribution of feeders (artificial flowers) and scent-marking locations (branches), and varied nectar delivery rates, to assess effects on foraging, scent-marking, and patrolling. Males responded strongly to spatial structure: in clumped arrays with evenly spaced resources, movements between consecutive visits were shorter and more localized, while in dispersed arrays with irregular spacing, transitions were longer and more variable. The combination of dispersed spacing and low nectar availability imposed the highest foraging demands, resulting in fewer feeding events and reduced total feeding time. Despite these increased costs, males maintained consistent investment in reproductive behaviors, suggesting a prioritization of mate-seeking over energy gain. Rather than reducing signaling, males adjusted their foraging strategy—favoring fewer but prolonged feeding bouts when nectar availability allowed. These findings reveal a unidirectional behavioral adjustment, in which foraging is modulated to sustain reproductive effort, and show how spatial resource structure and nectar availability together shape movement decisions in male pollinators.

Rapid learning of aversive stimuli is adaptive, but the persistence of the avoidance response in the absence of further reinforcement might depend on the severity of the adverse experience. For example, an experience involving injury would be expected to lead to more durable memory than the mere exposure to an unpleasant tastant, especially when new experiences indicate that the aversive stimulus is no longer present. We investigated how bumblebees (Bombus terrestris) learn and retain associations between flower colours and two types of aversive stimuli: electric shock and saturated salt (NaCl) solution. Using a conditioning paradigm, we examined how these stimuli influence avoidance learning across foraging bouts and tracked the process of extinction learning, the formation of new memory in response to the absence of the reinforcement, over two weeks. Our results show that bees rapidly learn to avoid both stimuli, and reach >90% accuracy of avoidance after six foraging bouts. We then examined how bees modified their avoidance behaviour in the absence of further aversive stimulation. Testing extinction learning on days 1, 3, 5, 7 and 14, we found that electric shock as a nociceptive stimulus induces a more persistent avoidance response, whereas exposure to the salt by engaging gustatory aversion pathways leads to a three times faster extinction rate. This suggests that although the initial training leads to equal levels of avoidance for both stimuli, bumblebees might display greater behavioural flexibility when updating the association between a colour and an unpleasant taste in comparison to a potentially injurious stimulus.

During high-speed behaviour, animals must synchronise perception and action despite rapid environmental and self-generated motion. How neural systems achieve such precision remains unclear. Here we show how the housefly ( Musca domestica ) maintains visual accuracy during fast motion. Using intracellular and photomechanical recordings during saccade-like stimulation, we traced information flow from photoreceptors to large monopolar cells (LMCs). Visual neurons achieved record-high information sampling (~2500 bits·s ^-1 ) and synaptic transmission (~4100 bits·s ^-1 ), far exceeding previous estimates. We identify a previously unknown mechanism - synaptic high-frequency jumping - in which photoreceptor-LMC synapses dynamically shift transmission toward higher frequencies during saccades, extending visual bandwidth to ~1000 Hz, effectively eliminating synaptic delays, and quadrupling classical flicker-fusion limits (~230 Hz). Behavioural experiments show flies respond synchronously within ~13-20 ms, even before photoreceptor responses peak. A biophysically realistic model reveals how photomechanical-stochastic-refractory quantal sampling and synaptic transmission co-adapt with saccadic behaviour: through self-motion, flies efficiently translate image motion into temporally-precise, predictive high-speed vision.

The honey bee waggle dance, which encodes food location, is often thought to involve only one-way information transfer from dancers to signal receivers. Here, we show that the information content of the dance is influenced by the presence of followers and the number of appropriately aged potential followers in the hive, rather than the total number of bees on the dance floor. Dancers reduced the precision of directional and distance communication when they had fewer actual and potential followers. Even when the dance floor was crowded with young bees that do not follow dances, dancers showed the same declines in precision. These declines appear to arise as a byproduct of audience seeking during the return run, when dancers with fewer followers spent more time moving and covered greater distances across the dance floor. Although their mean waggle run duration and the distance covered per waggle run remained unchanged, both measures became markedly more variable when followers were scarce. Dancers likely use quorum sensing of tactile contacts and, potentially, age-specific odors to sense audience size. These results reveal that waggle dancing is a socially responsive process shaped by feedback from followers, demonstrating bidirectional information flow within this communication system.

Consciousness is a state of subjective experience or awareness, e.g. of an emotion, the self or external objects. In humans, this awareness is underpinned by a suite of cognitive functions, from attention to metacognition. To understand the evolution of consciousness, the study of these cognitive functions across a variety of animal taxa is critical. Insects are useful organisms because we have a sophisticated understanding of their cognition from over a century of study and modern tools are revealing the intricacies of insect brains with increasing clarity. Here we cover the rich history of this venerable field as well as more recent discoveries relating to consciousness in insects, specifically focusing on the following areas: emotions, the distinction of self and other, prediction, attention and active sleep. There can still be no formal certainty about consciousness in insects; even in humans, there is currently no agreement over the particular combination of cognition and neural function that produces consciousness. Nonetheless, evidence from all the lines of investigation summarized here builds up to an increasing probability that insects might possess some form of subjective experience. We encourage further investigation of insects to explore the building blocks of consciousness and its evolutionary antecedents. This article is part of the theme issue ‘Evolutionary functions of consciousness’.