Route retracing: way pointing and multiple vector memories in trail-following ants.

Maintaining positional estimates of goal locations is a fundamental task for navigating animals. Diverse animal groups, including both vertebrates and invertebrates, can accomplish this through path integration. During path integration, navigators integrate movement changes, tracking both distance and direction, to generate a spatial estimate of their start location, or global vector, allowing efficient direct return travel without retracing the outbound route. In ants, path integration is accomplished through the coupling of pedometer and celestial compass estimates. Within path integration, it has been theorized navigators may use multiple vector memories for way pointing. However, in many instances, these navigators may instead be homing via view alignment. Here, we present evidence that trail-following ants can attend to segments of their global vector to retrace their non-straight pheromone trails, without the confound of familiar views. Veromessor pergandei foragers navigate to directionally distinct intermediate sites via path integration by orienting along separate legs of their inbound route at unfamiliar locations, indicating these changes are not triggered by familiar external cues, but by vector state. These findings contrast with path integration as a singular memory estimate in ants and underscore the system's ability to way point to intermediate goals along the inbound route via multiple vector memories, akin to trapline foraging in bees visiting multiple flower patches. We discuss how reliance on non-straight pheromone-marked trails may support attending to separate vectors to remain on the pheromone rather than attempting straight-line shortcuts back to the nest.

Directed retreat and navigational mechanisms in trail following Formica obscuripes.

Ant species exhibit behavioural commonalities when solving navigational challenges for successful orientation and to reach goal locations. These behaviours rely on a shared toolbox of navigational strategies that guide individuals under an array of motivational contexts. The mechanisms that support these behaviours, however, are tuned to each species' habitat and ecology with some exhibiting unique navigational behaviours. This leads to clear differences in how ant navigators rely on this shared toolbox to reach goals. Species with hybrid foraging structures, which navigate partially upon a pheromone-marked column, express distinct differences in their toolbox, compared to solitary foragers. Here, we explore the navigational abilities of the Western Thatching ant (Formica obscuripes), a hybrid foraging species whose navigational mechanisms have not been studied. We characterise their reliance on both the visual panorama and a path integrator for orientation, with the pheromone's presence acting as a non-directional reassurance cue, promoting continued orientation based on other strategies. This species also displays backtracking behaviour, which occurs with a combination of unfamiliar terrestrial cues and the absence of the pheromone, thus operating based upon a combination of the individual mechanisms observed in solitarily and socially foraging species. We also characterise a new form of goalless orientation in these ants, an initial retreating behaviour that is modulated by the forager's path integration system. The behaviour directs disturbed inbound foragers back along their outbound path for a short distance before recovering and reorienting back to the nest.

Varieties of visual navigation in insects.

The behaviours and cognitive mechanisms animals use to orient, navigate, and remember spatial locations exemplify how cognitive abilities have evolved to suit a number of different mobile lifestyles and habitats. While spatial cognition observed in vertebrates has been well characterised in recent decades, of no less interest are the great strides that have also been made in characterizing and understanding the behavioural and cognitive basis of orientation and navigation in invertebrate models and in particular insects. Insects are known to exhibit remarkable spatial cognitive abilities and are able to successfully migrate over long distances or pinpoint known locations relying on multiple navigational strategies similar to those found in vertebrate models-all while operating under the constraint of relatively limited neural architectures. Insect orientation and navigation systems are often tailored to each species' ecology, yet common mechanistic principles can be observed repeatedly. Of these, reliance on visual cues is observed across a wide number of insect groups. In this review, we characterise some of the behavioural strategies used by insects to solve navigational problems, including orientation over short-distances, migratory heading maintenance over long distances, and homing behaviours to known locations. We describe behavioural research using examples from a few well-studied insect species to illustrate how visual cues are used in navigation and how they interact with non-visual cues and strategies.

Good news is better than bad news, but bad news is not worse than no news.

Under certain conditions, pigeons will reliably prefer an alternative that leads to a lower probability of food over an alternative that leads to a higher probability of food (i.e., demonstrate suboptimal choice). A critical aspect of the typical procedure is that the alternative associated with less food provides differential stimuli that signal trial outcomes, but the alternative associated with more food does not. Few studies have investigated how partial signaling of an alternative influences preference. In Experiments 1-3, pigeons chose between two alternatives that each led to food 60% of the time with partially signaled trial outcomes. One alternative occasionally provided a stimulus that always preceded food (i.e., "good news") and the other alternative occasionally provided a stimulus that always preceded no food ("bad news"). Experiments 2 and 3 also assessed preference in conditions in which alternatives were either completely unsignaled (provided no differential stimuli) or always led to food. Pigeons consistently preferred the "good news" alternative over the "bad news" alternative and preferred 100% food over the "bad news" alternative. The results from conditions in which pigeons chose between the "bad news" alternative and an unsignaled alternative were inconclusive, but suggestive of a preference for bad news. The results are used to evaluate and distinguish between competing explanations of suboptimal choice.

Encoding Context Determines Risky Choice.

Both memory and choice are influenced by context: Memory is enhanced when encoding and retrieval contexts match, and choice is swayed by available options. Here, we assessed how context influences risky choice in an experience-based task in two main experiments (119 and 98 participants retained, respectively) and two additional experiments reported in the Supplemental Material available online (152 and 106 participants retained, respectively). Within a single session, we created two separate contexts by presenting blocks of trials in distinct backgrounds. Risky choices were context dependent; given the same choice, people chose differently depending on other outcomes experienced in that context. Choices reflected an overweighting of the most extreme outcomes within each local context rather than the global context of all outcomes. When tested in the nontrained context, people chose according to the context at encoding and not retrieval. In subsequent memory tests, people displayed biases specific to distinct contexts: Extreme outcomes from each context were more accessible and judged as more frequent. These results pose a challenge for theories of choice that rely on retrieval as guiding choice.

Role of the pheromone for navigation in the group foraging ant, Veromessor pergandei.

Navigation is comprised of a variety of strategies which rely on multiple external cues to shape a navigator's behavioral output. Here, we explored in the ant Veromessor pergandei, the interactions between the information provided by the pheromone trail and the home vector guided by the celestial compass. We found that a cross sensory interaction between the pheromone cue and the path integrator underlies correct orientation during the inbound journey. The celestial compass provides directional information, while the presence of the trail pheromone acts as a critical context cue, triggering distinct behaviors (vector orientation, search, and backtracking). While exposed to the pheromone, foragers orient to the vector direction regardless of vector state, while in the pheromone's absence, the current remaining vector determines the forager's navigational behavior. This interaction also occurs in foragers with no remaining path integrator, relying on the activation of a celestial compass-based memory of the previous trip. Such cue interactions maximize the foragers' return to the nest and inhibit movement off the pheromone trail. Finally, our manipulations continuously rotated foragers away from their desired heading, yet foragers were proficient at counteracting these changes, steering to maintain a correct compass heading even at rotational speeds of ~ 40°/s.

Pheromone cue triggers switch between vectors in the desert harvest ant, Veromessor pergandei.

The desert harvester ant (Veromessor pergandei) employs a mixture of social and individual navigational strategies at separate stages of their foraging trip. Individuals leave the nest along a pheromone-based column, travelling 3-40 m before spreading out to forage individually in a fan. Foragers use path integration while in this fan, accumulating a direction and distance estimate (vector) to return to the end of the column (column head), yet foragers' potential use of path integration in the pheromone-based column is less understood. Here we show foragers rely on path integration both in the foraging fan and while in the column to return to the nest, using separate vectors depending on their current foraging stage in the fan or column. Returning foragers displaced while in the fan oriented and travelled to the column head location while those displaced after reaching the column travel in the nest direction, signifying the maintenance of a two-vector system with separate fan and column vectors directing a forager to two separate spatial locations. Interestingly, the trail pheromone and not the surrounding terrestrial cues mediate use of these distinct vectors, as fan foragers briefly exposed to the pheromone cues of the column in isolation altered their paths to a combination of the fan and column vectors. The pheromone acts as a contextual cue triggering both the retrieval of the column-vector memory and its integration with the forager's current fan-vector.

The Near-Miss Effect in Slot Machines: A Review and Experimental Analysis Over Half a Century Later.

In games of chance, a near miss is said to occur when feedback for a loss approximates a win. For instance, obtaining "cherry-cherry-lemon" on a slot machine could be considered a near miss. Sixty-six years ago, B.F. Skinner first proposed the idea that near-miss events might reinforce continued play in slot machines, and despite some inconsistencies in the experimental literature, belief in this "near-miss effect" has remained strong. In the present manuscript, we will review this literature and present experimental assessments of the near-miss effect on the frequency of the gambling response. Experiment 1 used a tightly controlled resistance-to-extinction procedure in pigeons to evaluate the putative reinforcing effect of near misses relative to a control "far-miss" reel pattern. Experiment 2 extended Experiment 1's procedure to human participants. The results of both experiments failed to support the near-miss effect hypothesis. Experiment 3 used a further simplified procedure to assess the validity of the resistance-to-extinction paradigm when a probable conditional reinforcer was present on the reel stimuli. Although a clear conditional response was obtained from the reel, subsequent testing in extinction revealed no conditionally reinforcing function of this stimulus on operant response frequency.

Terrestrial cue learning and retention during the outbound and inbound foraging trip in the desert ant, Cataglyphis velox.

Foraging ants are able to acquire and retain long-term memories of panorama cues around the nest and along known routes. Here we explore foragers' ability to learn and retain skyline cues experienced on only the outbound or inbound portion of the foraging trip. Foragers exposed to the skyline on the outbound portion showed single trial learning of these cues. Furthermore, the navigational performance of these "Outbound-Only" foragers was on par with foragers that experienced the full route. In contrast, foragers experiencing the skyline only on the inbound portion, "Inbound-Only" foragers, took 5 trips to successfully learn these cues. These performance differences persisted for long-term memory retention. Outbound-Only foragers successfully oriented after a 3-day delay and showed similar performance to the full route control, whereas Inbound-Only foragers were no longer able to orient successfully to these cues after 3 days. Additionally, long-term memory formation of skyline cues appears to require multiple presentations, as foragers with only one outbound experience of the skyline could not successfully orient after the delay. Our results suggest that terrestrial cue learning and retention is more robust when cues are experienced on the outbound segment of the foraging trip.

Not just going with the flow: foraging ants attend to polarised light even while on the pheromone trail.

The polarisation pattern of skylight serves as an orientation cue for many invertebrates. Solitary foraging ants, in particular, rely on polarised light to orient along with a number of other visual cues. Yet it is unknown, if this cue is actively used in socially foraging species that use pheromone trails to navigate. Here, we explore the use of polarised light in the presence of the pheromone cues of the foraging trail. The desert harvester ant, Veromessor pergandei, relies on pheromone cues and path integration in separate stages of their foraging ecology (column and fan, respectively). Here, we show that foragers actively orient to an altered overhead polarisation pattern, both while navigating individually in the fan and while on the pheromone-based column. These heading changes occurred during twilight, as well as in the early morning and late afternoon before sunset. Differences in shift size indicate that foragers attend to both the polarisation pattern and the sun's position when available, yet during twilight, headings are dominated by the polarisation pattern. Finally, when the sun's position was experimentally blocked before sunset, shift sizes increased similar to twilight testing. These findings show that celestial cues provide directional information on the pheromone trail.

Odometry and backtracking: social and individual navigation in group foraging desert harvester ants (Veromessor pergandei).

Veromessor pergandei harvester ants are group foragers which use a combination of social cues (pheromone-marked columns) and individual cues (e.g., self-generated movement, visual cues) when exploring foraging areas for resources. Upon finding food, individuals navigate back to the column, which guides their return to the nest. The direction and length of columns change between foraging bouts, and hence the end of the column (unlike the nest location) is non-stationary. We conducted displacement tests on returning foragers and present three novel findings. First, returning individual ants accurately estimate their distance from the foraging area to the end of the column. Second, ants that reached the column but only traveled a small proportion of the distance to the nest either show homeward or random orientation; random orientation was seen when the column was long. Third, ants that have traveled most of the way back to the nest along the column show backtracking when they are displaced-orienting in the direction opposite to the nest-similar to Australian desert ants Melophorus bagoti. This commonality suggests that some navigation strategies are general across species, and are utilized by ants that navigate individually or socially.

Chickadees discriminate contingency reversals presented consistently, but not frequently.

Chickadees are high-metabolism, non-migratory birds, and thus an especially interesting model for studying how animals follow patterns of food availability over time. Here, we studied whether black-capped chickadees (Poecile atricapillus) could learn to reverse their behavior and/or to anticipate changes in reinforcement when the reinforcer contingencies for each stimulus were not stably fixed in time. In Experiment 1, we examined the responses of chickadees on an auditory go/no-go task, with constant reversals in reinforcement contingencies every 120 trials across daily testing intervals. Chickadees did not produce above-chance discrimination; however, when trained with a procedure that only reversed after successful discrimination, chickadees were able to discriminate and reverse their behavior successfully. In Experiment 2, we examined the responses of chickadees when reversals were structured to occur at the same time once per day, and chickadees were again able to discriminate and reverse their behavior over time, though they showed no reliable evidence of reversal anticipation. The frequency of reversals throughout the day thus appears to be an important determinant for these animals' performance in reversal procedures.

Sensitivity of the avian motion system to light and dark stimuli.

Global motion perception is important for mobile organisms. In laterally eyed birds, global motion appears to be processed in the entopallium, a neural structure that is part of the tectofugal pathway. Electrophysiological research has shown that motion selective cells in the entopallium are most responsive to small dark moving targets. Here, we investigated whether this bias toward dark targets of entopallial cells is mirrored by perceptual performance in a motion detection task in pigeons. We measured the detection thresholds of pigeons using random dot stimuli that consisted of either black or white dots on a gray background. We found that thresholds were significantly lower when using black dots as opposed to white dots. This heightened sensitivity is also noted in the learning rates of the pigeons. That is, we found that the pigeons learned the detection task significantly faster when the stimuli consisted of black dots. We believe that our results have important implications for the understanding of the functional role of the entopallium and the ON and OFF pathways in the avian motion system.

The contribution of nonrigid motion and shape information to object perception in pigeons and humans.

The ability to perceive and recognize objects is essential to many animals, including humans. Until recently, models of object recognition have primarily focused on static cues, such as shape, but more recent research is beginning to show that motion plays an important role in object perception. Most studies have focused on rigid motion, a type of motion most often associated with inanimate objects. In contrast, nonrigid motion is often associated with biological motion and is therefore ecologically important to visually dependent animals. In this study, we examined the relative contribution of nonrigid motion and shape to object perception in humans and pigeons, two species that rely extensively on vision. Using a parametric morphing technique to systematically vary nonrigid motion and three-dimensional shape information, we found that both humans and pigeons were able to rely solely on either shape or nonrigid motion information to identify complex objects when one of the two cues was degraded. Humans and pigeons also showed similar 80% accuracy thresholds when the information from both shape and motion cues were degraded. We argue that the use of nonrigid motion for object perception is evolutionarily important and should be considered in general theories of vision at least with respect to visually sophisticated animals.

Pigeons perform poorly on a midsession reversal task without rigid temporal regularity.

Animals make surprising anticipatory and perseverative errors when faced with a midsession reversal of reinforcer contingencies on a choice task with highly predictable stimulus-time relationships. In the current study, we asked whether pigeons would anticipate changes in reinforcement when the reinforcer contingencies for each stimulus were not fixed in time. We compared the responses of pigeons on a simultaneous choice task when the initially correct stimulus was randomized or alternated across sessions. Pigeons showed more errors overall compared with the typical results of a standard midsession reversal procedure, and they did not show the typical anticipatory errors prior to the contingency reversal. Probe tests that manipulated the spacing between trials also suggested that timing of the session exerted little control of pigeons' behavior. The temporal structure of the experimental session thus appears to be an important determinant for animals' use of time in midsession reversal procedures.

Multiple cue use and integration in pigeons (Columba livia).

Encoding multiple cues can improve the accuracy and reliability of navigation and goal localization. Problems may arise, however, if one cue is displaced and provides information which conflicts with other cues. Here we investigated how pigeons cope with cue conflict by training them to locate a goal relative to two landmarks and then varying the amount of conflict between the landmarks. When the amount of conflict was small, pigeons tended to integrate both cues in their search patterns. When the amount of conflict was large, however, pigeons used information from both cues independently. This context-dependent strategy for resolving spatial cue conflict agrees with Bayes optimal calculations for using information from multiple sources.

Look up: Human adults use vertical height cues in reorientation.

Numerous studies have shown that people and other animals readily use horizontal geometry (distance and directional information) to reorient, and these cues sometimes dominate over other cues when reorienting in navigable environments. Our study investigated whether horizontal cues (distance/angle) dominate over vertical cues (wall height) when they are in conflict. Adult participants learned two locations (opposite corners) in either a rectangular room (with distance information) or a rhombus room (with angle information). Both training rooms had 2 opposite high walls as height cues. On each trial, participants were disoriented and then asked to locate the correct corners. In testing, the rooms were modified to provide (a) distance or angle cues only, (b) height cues only, and (c) both height and horizontal cues in conflict. Participants located the correct corners successfully with horizontal (distance/angle) or height cues alone. On conflict tests, participants did not show preference for the horizontal information (distance/angle) over the height cues. The results are discussed in terms of the geometric module theory and the adaptive combination theory.

Re-evaluating birds' ability to detect Glass patterns.

Glass patterns (GPs) are static stimuli that consist of randomly positioned dot-pairs that are spatially integrated to create the perception of a global form. However, when multiple independently generated static GPs are presented sequentially (termed 'dynamic' GP), observers report a percept of coherent motion, and data show an improvement in sensitivity. This increased sensitivity has been attributed to a summation of the form signals provided by the individual GPs. In Experiment 1, we tested whether pigeons also show a heightened sensitivity to dynamic GPs. Our results show that pigeons are significantly better at learning to discriminate dynamic GPs from noise compared with static GPs. However, in contrast to previous research, we found that pigeons did not perform well enough with our static GPs to extract sensitivity measurements. In Experiment 2, we compared our static GPs to those that have been used previously. We show that the difference in the comparison noise patterns is important. We used dipole noise patterns, while previous studies used uniform noise patterns that differ in mean dot spacing to the S+. We argue that prior findings from the use of GPs in pigeons should be re-evaluated using dynamic GP stimuli with noise that consist of dipoles.