Learning and organization of within-session sequences by pigeons (Columba livia).

Most animals engage in complex activities that are the combination of simpler actions expressed over a period of time. The mechanisms organizing such sequential behavior have been of long-standing biological and psychological interest. Previously, we observed pigeons' anticipatory behavior with a within-session sequence involving four choice alternatives suggestive of a potential understanding of the overall order and sequence of the items within a session. In that task, each colored alternative was correct for 24 consecutive trials as presented in a predictable sequence (i.e., A first, then B, then C, then D). To test whether these four already-trained pigeons possessed a sequential and linked representation of the ABCD items, we added a second four-item sequence involving new and distinct colored choice alternatives (i.e., E first for 24 trials, then F, then G, then H) and then alternated these ABCD and EFGH sequences over successive sessions. Over three manipulations, we tested and trained trials composed of combinations of elements from both sequences. We determined that pigeons did not learn any within-sequence associations among the elements. Despite the availability and explicit utility of such sequence cues, the data suggest instead that pigeons learned the discrimination tasks as a series of temporal associations among independent elements. This absence of any sequential linkage is consistent with the hypothesis that such representations are difficult to form in pigeons. This pattern of data suggests that for repeated sequential activities in birds, and potentially other animals including humans, there are highly effective, but underappreciated, clock-like mechanisms that control the ordering of behaviors.

Mechanisms of within-session sequential behavior in pigeons.

Correctly and efficiently selecting among options is critical to the organization of behavior across different time scales (minutes, days, seasons). As a result, understanding the mechanisms underlying the sequential behavior of animals has been a long-standing aim. In three experiments, four pigeons were tested in a four-choice simultaneous color discrimination. Across a session, they had to sequentially select a colored stimulus, and the correct color changed over four 24-trial phases (A→B→C→D). After learning this ABCD within-session sequence, tests identified that both timing and outcome feedback mechanisms contributed to the organization of pigeons' behavior. Different representational mechanisms are considered as accounts for the pigeons' observed sequential behavior.

Perceptual grouping and detection of trial-unique emergent structures by pigeons.

Detecting global patterns in the environment is essential to object perception and recognition. Consistent with this, pigeons have been shown to readily detect and locate geometrically arranged, structured targets embedded in randomized backgrounds. Here we show for the first time that pigeons can detect and localize trial-unique targets derived solely from global patterns resulting from periodicity, symmetry and their combination using randomly generated segments of black and white local elements. The results indicate pigeons can perceptually segment and detect a wide variety of emergent global structures and do so even when they are unique to each trial. The perceptual and cognitive mechanisms underlying this discrimination likely play important roles in the abilities of how pigeons, and likely other birds, detect and categorize the properties of natural objects at different spatial scales.

Towards describing scenes by animals: Pigeons' ordinal discrimination of objects varying in depth.

The perception of a complex scene requires visual mechanisms that include identifying objects and their relative placement in depth. To examine apparent depth perception in birds, we tested four pigeons with a novel multiple-sequential-choice procedure. We created 3D-rendered scene stimuli containing three objects located at different apparent depths based on a variety of pictorial cues and placed small circular target response areas on them. The pigeons were trained to sequentially choose among the multiple response areas to report the object closest in apparent depth (ordinal position; front then middle object). After the pigeons learned this sequential depth discrimination, their use of three different monocular depth cues (occlusion, relative size, height in field) was tested, and their flexibility evaluated using three novel objects. In addition to the contribution to understanding apparent depth perception in birds, the use of more flexible open-ended choice discriminations, as employed here, has considerable promise for creating informative production-like tasks in nonverbal animals.

Pigeons process actor-action configurations more readily than bystander-action configurations.

Behavior requires an actor. Two experiments using complex conditional action discriminations examined whether pigeons privilege information related to the digital actor who is engaged in behavior. In Experiment 1, each of two video displays contained a digital model, one an actor engaged in one of two behaviors (Indian dance or martial arts) and one a neutrally posed bystander. To correctly classify the display, the pigeons needed to conditionally process the action in conjunction with distinctive physical features of the actor or the bystander. Four actor-conditional pigeons learned to correctly discriminate the actions based on the identity of the actors, whereas four bystander-conditional birds failed to learn. Experiment 2 established that this failure was not due to the latter group's inability to spatially integrate information across the distance between the two models. Potentially, the colocalization of the relevant model identity and the action was critical due to a fundamental configural or integral representation of these properties. These findings contribute to our understanding of the evolution of action recognition, the recognition of social behavior, and forms of observational learning by animals.

Natural disasters and infectious disease in Europe: a literature review to identify cascading risk pathways.

BACKGROUND: Natural disasters are increasing in their frequency and complexity. Understanding how their cascading effects can lead to infectious disease outbreaks is important for developing cross-sectoral preparedness strategies. The review focussed on earthquakes and floods because of their importance in Europe and their potential to elucidate the pathways through which natural disasters can lead to infectious disease outbreaks. METHODS: A systematic literature review complemented by a call for evidence was conducted to identify earthquake or flooding events in Europe associated with potential infectious disease events. RESULTS: This review included 17 peer-reviewed papers that reported on suspected and confirmed infectious disease outbreaks following earthquakes (4 reports) or flooding (13 reports) in Europe. The majority of reports related to food- and water-borne disease. Eleven studies described the cascading effect of post-disaster outbreaks. The most reported driver of disease outbreaks was heavy rainfall, which led to cross-connections between water and other environmental systems, leading to the contamination of rivers, lakes, springs and water supplies. Exposure to contaminated surface water or floodwater following flooding, exposure to animal excreta and post-disaster living conditions were among other reported drivers of outbreaks. CONCLUSIONS: The cascade effects of natural disasters, such as earthquakes and floods, include outbreaks of infectious disease. The projection that climate change-related extreme weather events will increase in Europe in the coming century highlights the importance of strengthening preparedness planning and measures to mitigate and control outbreaks in post-disaster settings.

An identified ensemble within a neocortical circuit encodes essential information for genetically-enhanced visual shape learning.

Advanced cognitive tasks are encoded in distributed neocortical circuits that span multiple forebrain areas. Nonetheless, synaptic plasticity and neural network theories hypothesize that essential information for performing these tasks is encoded in specific ensembles within these circuits. Relatively simpler subcortical areas contain specific ensembles that encode learning, suggesting that neocortical circuits contain such ensembles. Previously, using localized gene transfer of a constitutively active protein kinase C (PKC), we established that a genetically-modified circuit in rat postrhinal cortex, part of the hippocampal formation, can encode some essential information for performing specific visual shape discriminations. However, these studies did not identify any specific neurons that encode learning; the entire circuit might be required. Here, we show that both learning and recall require fast neurotransmitter release from an identified ensemble within this circuit, the transduced neurons; we blocked fast release from these neurons by coexpressing a Synaptotagmin I siRNA with the constitutively active PKC. During learning or recall, specific signaling pathways required for learning are activated in this ensemble; during learning, calcium/calmodulin-dependent protein kinase II, MAP kinase, and CREB are activated; and, during recall, dendritic protein synthesis and CREB are activated. Using activity-dependent gene imaging, we showed that during learning, activity in this ensemble is required to recruit and activate the circuit. Further, after learning, during image presentation, blocking activity in this ensemble reduces accuracy, even though most of the rest of the circuit is activated. Thus, an identified ensemble within a neocortical circuit encodes essential information for performing an advanced cognitive task.

Perception of Ebbinghaus-Titchener stimuli in starlings (Sturnus vulgaris).

Whether animals experience visual illusions is a fertile area of study for examining the evolution and operation of visual cognition across different species. Here, five starlings were tested to examine whether they experienced the Ebbinghaus-Titchener illusion. Across two experiments using an absolute target circle size discrimination, the size, similarity, distance, and number of the surrounding flankers were manipulated. The results suggest that this passerine species exhibits behavior inconsistent with the perception of the illusion, neither in a human-like fashion nor, as suggested by the first experiment, a reversed illusion. Instead, the typical training used to investigate this illusion caused the starlings to learn to integrate the irrelevant flankers into their decision process in a manner that precludes the study of illusory perception. The resulting discriminative behavior might best be described using a template-matching account. While illusion perception by animals remains an important comparative question, it requires additional validation to confirm the exact mechanisms of any illusory reports.

"Insight" in pigeons: absence of means-end processing in displacement tests.

The understanding of functional relations between action and consequence is a critical component of intelligence. To examine this linkage in pigeons, we investigated their understanding of the relations of the elements tested in an extension of Köhler's box stacking task to this species. In the experiments, the pigeons had to move a spatially displaced box under an out-of-reach target. Experiment 1 successfully replicated and extended the previous finding showing that when separately trained to move a box and stand on it to peck the target, pigeons can synthesize these behaviors to solve the single-box displacement problem quickly on their first attempt. Experiment 2 tested whether pigeons, when given a simultaneous choice between two boxes with identical reinforcement histories, would selectively choose the box with the correct functional affordance (i.e., permitting standing) to solve the problem rather than a non-functional one. Their extensive, equivalent, and undirected behavior in moving both boxes during these tests suggests the pigeons did not possess a means-end understanding of the functional properties of the boxes. Instead, their results were consistent with an analysis of their earlier synthetic behavior as being due to the temporal and spatial relations of the physical elements in the task and their prior learned behaviors.

Visual control of an action discrimination in pigeons.

Recognizing and categorizing behavior is essential for all animals. The visual and cognitive mechanisms underlying such action discriminations are not well understood, especially in nonhuman animals. To identify the visual bases of action discriminations, four pigeons were tested in a go/no-go procedure to examine the contribution of different visual features in a discrimination of walking and running actions by different digital animal models. Two different tests with point-light displays derived from studies of human biological motion failed to support transfer of the learned action discrimination from fully figured models. Tests with silhouettes, contours, and the selective deletion or occlusion of different parts of the models indicated that information about the global motions of the entire model was critical to the discrimination. This outcome, along with earlier results, suggests that the pigeons' discrimination of these locomotive actions involved a generalized categorization of the sequence of configural poses. Because the motor systems for locomotion and flying in pigeons share little in common with quadruped motions, the pigeons' discrimination of these behaviors creates problems for motor theories of action recognition based on mirror neurons or related notions of embodied cognition. It suggests instead that more general motion and shape mechanisms are sufficient for making such discriminations, at least in birds.

Impact of equivalence class training on same/different learning by pigeons.

Separating and isolating the contributions of perception to concept formation in animals has been a long-standing and persistent challenge. Here we describe a novel approach to assessing this question by using equivalence training consisting of unrelated images as the basis for subsequent same/different (S/D) learning. Following equivalence class training, two groups of pigeons attempted to learn a go/no-go discrimination task constructed from these classes. In the go/no-go task, a consistent group was given an S/D assignment that aligned with this prior training (same vs. different classes). An inconsistent group was given go/no-go assignments that were misaligned with their established classes. The consistent group exhibited better learning and stimulus control in their S/D task than did the inconsistent group. These results suggest that pigeons can use trained properties derived from class-based information to learn an S/D task without the aid of perceptual similarity. This novel approach holds promise for helping to evaluate the contribution of perceptual similarity to different types of concept learning. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Identified circuit in rat postrhinal cortex encodes essential information for performing specific visual shape discriminations.

Learning theories hypothesize specific circuits encode essential information for performance. For simple tasks in invertebrates and mammals, the essential circuits are known, but for cognitive functions, the essential circuits remain unidentified. Here, we show that some essential information for performing a choice task is encoded in a specific circuit in a neocortical area. Rat postrhinal (POR) cortex is required for visual shape discriminations, protein kinase C (PKC) pathways mediate changes in neuronal physiology that support learning, and specific PKC genes are required for multiple learning tasks. We used direct gene transfer of a constitutively active PKC to prime a specific POR cortex circuit for learning visual shape discriminations. In the experiment, rats learned a discrimination, received gene transfer, learned new discriminations, received a small lesion that ablated approximately 21% of POR cortex surrounding the gene transfer site, and were tested for performance for discriminations learned either before or after gene transfer. Lesions of the genetically targeted circuit selectively interfered with performance for discriminations learned after gene transfer. Activity-dependent gene imaging confirmed increased activity in the genetically targeted circuit during learning and showed the essential information was sparse-coded in approximately 500 neurons in the lesioned area. Wild-type rats contained circuits with similar increases in activity during learning, but these circuits were located at unpredictable, different positions in POR cortex. These results establish that some essential information for performing specific visual discriminations can be encoded in a small, identified, neocortical circuit and provide a foundation for characterizing the circuit and essential information.

Pigeons discount continuously changing perspective during action recognition.

An important challenge for animal and artificial visual systems is separating the system's own motions from the movements of other animals or events. To examine this issue in birds, we conducted three experiments testing four pigeons in a go/no-go action discrimination. The pigeons discriminated whether a digital human model was exhibiting an extended series of articulated motions or one of a set of static poses from the same video. They were required to do so while the rendering camera's perspective changed continually during each trial's 20-s video presentation. Experiment 1 found that pigeons easily discount the camera's continuous motion. Experiments 2 and 3, by testing novel sequences of the behavior, novel behaviors, silhouettes, and a form of conditional discrimination, revealed this to be a general capacity. Overall, the discrimination was predominantly mediated by global action cues, although a small contribution of image-based statistical features was detected. Collectively, the experiments reveal pigeons can readily separate and discount constantly changing perspectives while processing others' actions. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Dynamically occluded action recognition by pigeons.

Identifying the behaviors of organisms is essential for an animal's survival. This ability is particularly challenged when the "actors" are dynamically occluded by other objects and become fragmented as they move through an environment. Even when fragmented in time and across space, humans readily recognize the behavior of these dynamically occluded objects and actors. How animals process such fragmented information, especially when involving motion, remains uncertain. In three experiments, we investigated the ability of six pigeons to discriminate between the running and walking actions of digital animal models when dynamically occluded. The pigeons were tested in a go/no-go procedure using three models that transited behind multiple occluders in a semirealistic scene. Without ever seeing the entirety of the animal model at one time, all the pigeons learned to discriminate among these two behaviors. This discrimination transferred to an unfamiliar model, transit direction, transiting rates, camera perspectives, and occluders. Tests with different static and dynamic features indicated that the pigeons relied on motion features for the discrimination, especially articulated motion. These experiments demonstrate that pigeons, like humans, can discriminate actions even when their view of the actor is fragmented in time and space.

Modeling within-session dynamics of categorical and item-memory mechanisms in pigeons.

Past studies have shown that pigeons can learn complex categories and can also remember large numbers of individual objects. In recent work, Cook et al. Psychonomic Bulletin & Review, 28, 548-555, (2021) provided evidence that pigeons may use a dynamic combination of both category-based information and item-specific memorization to solve a categorical variation of the mid-session reversal (MSR) task, which is an influential task for exploring the nature of temporally organized behaviors in animals. To provide greater insight into these pigeons' behaviors, in this article we developed and investigated different computational models and their variations to account for these data. Of these, two models emerged as good candidates. One was a multinomial-processing-tree categorization/memory model, formalizing the two-process mechanism initially proposed by Cook et al. Psychonomic Bulletin & Review, 28, 548-555, (2021). The second was a new object/time-coding model, which posits the storage of object-specific memories with an additional within-session time code and assumes that a basic stimulus generalization process underlies the pigeons' choice behavior. Both provided high-quality fits to the published sets of training and transfer data collected in the categorical MSR task. These computational efforts give deeper insights into the theoretical mechanisms underlying the temporal and sequential structure of behavior in animals and stimulate future empirical research further revealing the organization of the pigeons' cognitive processes.

Same/different discrimination of motion by pigeons.

Telling that one object or moment is different from another one is fundamental to cognition and intelligent behavior. Most investigations examining same/different (S/D) concepts in animals have relied on testing static visual stimuli. To move beyond this limitation, we investigated how five pigeons learned and performed a motion S/D discrimination. Using a go/no-go task, dynamic motion fields built from dot elements were presented in sequence to display repeating (same) or changing (different) motions. Each trial consisted of 10 motion segments presented in succession using the direction and rate of dot movement in the motion field to exemplify the S/D relations. The pigeons learned this motion S/D discrimination. We further tested their performance by varying the number and persistence of the dots in the motion fields. The results indicated the pigeons likely extracted globally integrated perceptual summaries of the motions for comparison across the segments. Testing differing organizations of the S/D relations across segments indicated that this discrimination could be determined from as few as two segments and involved an updating comparison of at least four or more segments of the sequence during their presentation. Collectively, the experiments establish for the first time that pigeons can use motion features to classify sequential same and different experiences. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

CaMKII, MAPK, and CREB are coactivated in identified neurons in a neocortical circuit required for performing visual shape discriminations.

Current theories postulate that the essential information for specific cognitive tasks is widely dispersed in multiple forebrain areas. Nonetheless, synaptic plasticity and neural network theories hypothesize that activation of specific signaling pathways, in specific neurons, modifies synaptic strengths, thereby encoding essential information for performance in localized circuits. Consistent with these latter theories, we have shown that gene transfer of a constitutively active protein kinase C into several hundred glutamatergic and GABAergic neurons in rat postrhinal cortex enhances choice accuracy in visual shape discriminations, and the genetically-modified circuit encodes some of the essential information for performance. However, little is known about the role of specific signaling pathways required for learning, in specific neurons within a critical circuit. Here we show that three learning-associated signaling pathways are coactivated in the transduced neurons during both learning and performance. After gene transfer, but before learning a new discrimination, the calcium/calmodulin-dependent protein kinase (CaMKII), MAP kinase, and CREB pathways were inactive. During learning, these three pathways were coactivated in the transduced neurons. During later performance of the discrimination, CaMKII activity declined, but MAP kinase and CREB activity persisted. Because the transduced neurons are part of a circuit that encodes essential information for performance, activation of these learning-associated signaling pathways, in these identified neurons, is likely important for both learning and performance.

Discrimination and categorization of actions by pigeons.

Recognizing and categorizing behavior is essential for animals (e.g., during mate selection, courtship, and avoidance of predators). In a study examining if and how animals classify different actions, a go/no-go procedure was used to train 4 pigeons to discriminate among "walking" and "running" digital animal models (each portrayed from 12 different viewpoints). Action discrimination acquired for two models significantly transferred to six novel animal models moving in novel and biomechanically characteristic ways. Randomization of frame order in the animated sequences, stimulus inversion, and static presentation all disrupted this discrimination, whereas changes in the direction and speed (both increases and decreases) of the actions did not. These results suggest that the pigeons discriminated the behaviors on the basis of generalized recognition of the models' sequence of poses across time and provide the best evidence yet that animals use action categories to identify contrasting behavioral units.

Use of different attentional strategies by pigeons and humans in multidimensional visual search.

To study comparative attentional allocation strategies, pigeons and humans were tested using simultaneously available discrimination tasks. Given visual search displays containing 32 items from two orthogonal dimensions, participants were reinforced for selecting the eight brightest (or darkest) of 16 brightness items and the eight most vertical (or horizontal) of 16 orientation items. Consistent with a sequential dimensional strategy, humans preferentially chose items from one dimension before switching to the other to complete the search. In contrast, the pigeons did not preferentially stay within one dimension over consecutive choices. Instead, they chose the items most likely to yield reward based on item discriminability. Computational models that incorporated a "dimensional staying" factor accounted best for the human data, while simulations using only discriminability reproduced the pigeons' data. These results suggest that humans are sensitive to the benefits of attentional staying and the costs of switching between dimensional tasks, while there was no evidence that these factors influenced the pigeons' choice behavior. These findings suggest fundamental differences in how pigeons and humans allocate attention in complex choice situations. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Adaptive testing of the critical features in 2D-shape discrimination by pigeons and starlings.

An innovative adaptive discrimination procedure examined how two bird species, pigeons and starlings, recognize and discriminate two-dimensional (2D) visual shapes. Prior results suggest a comparative divergence between mammals and birds in their relative reliance on vertices versus line segments to mediate discrimination. To address this potentially important difference, four pigeons and five starlings were tested with a square versus triangle discrimination in two experiments. An adaptive genetic algorithm guided the selection and organization of the training and test stimuli. Both species showed considerable flexibility in accurately selecting triangles despite wide variation in stimulus appearance and location. Most critically, Experiment 2 revealed that both bird species relied more on the figures' vertices during successful discrimination than their connecting line segments. This reliance was revealed by both traditional accuracy differences using contour-deleted displays and genetic algorithm-based shifts in "gene values" caused by the birds' selection. These results, in contrast to previous findings, indicate that mammals and birds likely converge in their reliance on vertices as a highly critical feature in visual shape discrimination. (PsycInfo Database Record (c) 2021 APA, all rights reserved).