Social context affects the motivation of laboratory mice, Mus musculus, to gain access to resources

Consumer demand studies measuring the motivation that animals have for resources have almost exclusively used gregarious species, but have tested animals housed in isolation. The motivation that gregarious animals have for resources could be increased or decreased by the presence or absence of companion animals, that is, the social context. I trained a single mouse from each of six groups to perform an operant task that was quantifiable and would not be performed fortuitously or learnt by nontrained mice. The trained mice were housed with nontrained cagemates in a start cage that required them to perform the operant task to enter a resource cage providing either additional space or a running wheel. The presence of cagemates in the start cage significantly decreased the number of visits/24 h to the running wheel, the number of bouts and the duration of wheel running, but had no effect on the number of visits to additional space. The presence of cagemates increased the time spent in the resource cage whether this provided additional space or a running wheel, indicating that the mice overcompensated for the reduced frequency of visits. These results show that social context can have a significant effect on the motivation that animals have for resources, and that this effect is resource dependent. The influence of social context should therefore be considered in the design and interpretation of consumer demand studies. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.       

Decision Making in Concurrent Multitasking: Do People Adapt to Task Interference?

While multitasking has received a great deal of attention from researchers, we still know little about how well people adapt their behavior to multitasking demands. In three experiments, participants were presented with a multicolumn subtraction task, which required working memory in half of the trials. This primary task had to be combined with a secondary task requiring either working memory or visual attention, resulting in different types of interference. Before each trial, participants were asked to choose which secondary task they wanted to perform concurrently with the primary task. We predicted that if people seek to maximize performance or minimize effort required to perform the dual task, they choose task combinations that minimize interference. While performance data showed that the predicted optimal task combinations indeed resulted in minimal interference between tasks, the preferential choice data showed that a third of participants did not show any adaptation, and for the remainder it took a considerable number of trials before the optimal task combinations were chosen consistently. On the basis of these results we argue that, while in principle people are able to adapt their behavior according to multitasking demands, selection of the most efficient combination of strategies is not an automatic process.     

A trade-off in task allocation between sensitivity to the environment and response time

Task allocation is the process that adjusts the number of workers in each colony task in response to the environment. There is no central coordination of task allocation; instead workers use local cues from the environment and from other workers to decide which task to perform. We examine two aspects of task allocation: the sensitivity to the environment of task distribution, and the rate of response to environmental changes. We investigate how these two aspects are influenced by: (1) colony size, and (2) behavioral rules used by workers, i.e. how a worker uses cues from the environment and from social interactions with other workers in deciding which task to perform. We show that if workers use social cues in their choice of task, response time decreases with increasing colony size. Sensitivity of task distribution to the environment may decrease or not with colony size, depending on the behavioral rules used by workers. This produces a trade-off in task allocation: short response times can be achieved by increasing colony size, but at the cost of decreased sensitivity to the environment. We show that when a worker's response to social interactions depends on the local environment, sensitivity of task distribution to the environment is not affected by colony size and the trade-off is avoided.     

Suppressing the Encoding of New Information in Memory: A Behavioral Study Derived from Principles of Hippocampal Function

Cognitive processes do not occur in isolation. Interactions between cognitive processes can be observed as a cost in performance following a switch between tasks, a cost that is greatest when the cognitive requirements of the sequential tasks compete. Interestingly, the long-term mnemonic goals associated with specific cognitive tasks can also directly compete. For example, encoding the sequential order in which stimuli are presented in the commonly-utilised 2-Back working memory (WM) tasks is counter-productive to task performance, as this task requires the continual updating of the contents of one''s current mental set. Performance of this task consistently results in reduced activity within the medial temporal lobe (MTL), and this response is believed to reflect the inhibitory mnemonic component of the task. Conversely, there are numerous cognitive paradigms in which participants are explicitly instructed to encode incoming information and performance of these tasks reliably increases MTL activity. Here, we explore the behavioural cost of sequentially performing two tasks with conflicting long-term mnemonic goals and contrasting neural profiles within the MTL. We hypothesised that performing the 2-Back WM prior to a hippocampal-dependent memory task would impair performance on the latter task. We found that participants who performed the 2-Back WM task, prior to the encoding of novel verbal/face-name stimuli, recollected significantly fewer of these stimuli, compared to those who had performed a 0-Back control task. Memory processes believed to be independent of the MTL were unaffected. Our results suggest that the inhibition of MTL-dependent mnemonic function persists beyond the cessation of the 2-Back WM task and can alter performance on entirely separate and subsequently performed memory tasks. Furthermore, they indicate that performance of such tasks may induce a temporarily-sustained, virtual lesion of the hippocampus, which could be used as a probe to explore cognitive processes in the absence of hippocampal involvement.     

Subjective Size Perception Depends on Central Visual Cortical Magnification in Human V1

In the Ebbinghaus illusion, the context surrounding an object modulates its subjectively perceived size. Previous work implicates human primary visual cortex (V1) as the neural substrate mediating this contextual effect. Here we studied in healthy adult humans how two different types of context (large or small inducers) in this illusion affected size perception by comparing each to a reference stimulus without any context. We found that individual differences in the magnitudes of the illusion produced by either type of context were correlated with V1 area defined through retinotopic mapping using functional MRI. However, participants'' objective ability to discriminate the size of objects presented in isolation was unrelated to illusion strength and did not correlate with V1 area. Control analyses showed no correlations between behavioral measures and the overall V1 area estimated probabilistically on the basis of neuroanatomy alone. Therefore, subjective size perception correlated with variability in central cortical magnification rather than the anatomical extent of primary visual cortex. We propose that such changes in subjective perception of size are mediated by mechanisms that scale with the extent to which an individual''s V1 selectively represents the central visual field.     

Postural control during the Stroop test in dyslexic and non dyslexic teenagers

Postural control in quiet stance although simple still requires some cognitive resources; dual cognitive tasks influence further postural control. The present study examines whether or not dyslexic teenagers experience postural instability when performing a Stroop dual task for which their performances are known to be poor. Fifteen dyslexics and twelve non-dyslexics (14 to 17 years old) were recruited from the same school. They were asked to perform three tasks: (1) fixate a target, (2) perform an interference Stroop test (naming the colour or the word rather than reading the word), (3) performing flexibility Stroop task: the subject performed the interference task as in (2) except when the word was in a box, in which case he had to read the word. Postural performances were measured with a force platform. The results showed a main task effect on the variance of speed of body sway only: such variance was higher in the flexibility task than for the other two tasks. No group effect was found for any of the parameters of posture (surface, mediolateral and anteroposterior sway, variance of speed). Further wavelet analysis in the time-frequency domain revealed an increase in the spectral power of the medium frequency range believed to be related to cerebellum control; an accompanying increase in the cancellation time of the high frequency band related to reflexive loops occurred for non-dyslexics only. These effects occurred for the flexibility task and could be due to its high cognitive difficulty. Dyslexics displayed shorter cancellation time for the medium frequency band for all tasks, suggesting less efficient cerebellar control, perhaps of eye fixation and attention influencing body sway. We conclude that there is no evidence for a primary posture deficit in 15 year old teenagers who come from the general population and who were recruited in schools.     

Division of labor in the hyperdiverse ant genus Pheidole is associated with distinct subcaste- and age-related patterns of worker brain organization

The evolutionary success of ants and other social insects is considered to be intrinsically linked to division of labor among workers. The role of the brains of individual ants in generating division of labor, however, is poorly understood, as is the degree to which interspecific variation in worker social phenotypes is underscored by functional neurobiological differentiation. Here we demonstrate that dimorphic minor and major workers of different ages from three ecotypical species of the hyperdiverse ant genus Pheidole have distinct patterns of neuropil size variation. Brain subregions involved in sensory input (optic and antennal lobes), sensory integration, learning and memory (mushroom bodies), and motor functions (central body and subesophageal ganglion) vary significantly in relative size, reflecting differential investment in neuropils that likely regulate subcaste- and age-correlated task performance. Worker groups differ in brain size and display patterns of altered isometric and allometric subregion scaling that affect brain architecture independently of brain size variation. In particular, mushroom body size was positively correlated with task plasticity in the context of both age- and subcaste-related polyethism, providing strong, novel support that greater investment in this neuropil increases behavioral flexibility. Our findings reveal striking levels of developmental plasticity and evolutionary flexibility in Pheidole worker neuroanatomy, supporting the hypothesis that mosaic alterations of brain composition contribute to adaptive colony structure and interspecific variation in social organization.     

Effects of the Ebbinghaus illusion on different behaviors: one- and two-handed grasping; one- and two-handed manual estimation; metric and comparative judgment

Many studies have suggested that visually-guided action is largely immune to the effects of several pictorial illusions that strongly influence perceptual judgments. The judgments in these experiments, however, have usually involved comparisons of multiple elements within a display, whereas the visually-guided actions have typically involved a pincer grip directed to only one display element. The three experiments presented here assess the influence of this confound on the perception versus action illusion dissociation. In general, the studies suggest (a) that the confound affects perceptual judgment but not grasping or manual estimation, and (b) that difficult visuomotor tasks are more affected by the Ebbinghaus illusion than easier tasks. In Experiment 1, participants reached for or made judgments about plastic disks placed in the center of the Ebbinghaus illusion display. Some participants reached for or made judgments about only the disk on the right, whereas others reached for or judged both disks simultaneously. A large effect of the illusion was found for grasping and comparative judgment, but not for manual estimation or metric judgment. In Experiment 2, the disks were elevated slightly to make gripping the targets easier, and the effects of the illusion on grasping were greatly reduced. For Experiment 3, participants performed the manual estimation task while the hands were placed in view, on the surface of the table, and the effects of the illusion were significantly increased. Taken together, the experiments indicate that task difficulty and hand visibility affect whether a task will be influenced by pictorial illusions or not. One- and two-handed grasping seem to be affected approximately equally.     

Neural Congruency Effects in the Multi-Source Interference Task Vanish in Healthy Youth after Controlling for Conditional Differences in Mean RT

According to the conflict monitoring model of cognitive control, reaction time (RT) in distracter interference tasks (e.g., the Stroop task) is a more precise index of response conflict than stimulus congruency (incongruent vs. congruent). The model therefore predicts that RT should be a reliable predictor of activity in regions of the posterior medial frontal cortex (pMFC) that are posited to detect response conflict. In particular, pMFC activity should be (a) greater in slow-RT than in fast-RT trials within a given task condition (e.g., congruent) and (b) equivalent in RT-matched trials from different conditions (i.e., congruent and incongruent trials). Both of these effects have been observed in functional magnetic resonance imaging (MRI) studies of adults. However, neither effect was observed in a recent study of healthy youth, suggesting that (a) the model does not accurately describe the relationship between RT and pMFC activity in this population or (b) the recent study was characterized by high variability due to a relatively small sample size. To distinguish between these possibilities, we asked a relatively large group of healthy youth (n = 28) to perform a distracter interference task - the multi-source interference task (MSIT) - while we recorded their brain activity with functional MRI. In this relatively large sample, both of the model’s predictions were confirmed. We conclude that the model accurately describes the relationship between pMFC activity and RT in healthy youth, but that additional research is needed to determine whether processes unrelated to response conflict contribute to this relationship.     

Modeling the time-dependent effect of the Ebbinghaus illusion on grasping

Various authors have reported a small but consistent effect of the Ebbinghaus illusion on the maximum opening of the hand during prehension. This effect has been interpreted in various ways. In the present study, we focus on the time-course of the effect of contextual elements on grasping. The analysis presented here is based on a model for the control of the digits that uses two movement parameters (the approach parameter and the intended contact positions). These two parameters are based on different spatial attributes (flanker-target distance and target-edge position). As we assume that the perception of both attributes is veridical, there is no need for on-line corrections in the model. We show that this model predicts all time-dependent effects of the Ebbinghaus display on grasping. Human behavior can show a reduction in context effects over time without assuming an underlying shift from illusory towards veridical size information.     

Generalization of motor learning depends on the history of prior action

Generalization of motor learning refers to our ability to apply what has been learned in one context to other contexts. When generalization is beneficial, it is termed transfer, and when it is detrimental, it is termed interference. Insight into the mechanism of generalization may be acquired from understanding why training transfers in some contexts but not others. However, identifying relevant contextual cues has proven surprisingly difficult, perhaps because the search has mainly been for cues that are explicit. We hypothesized instead that a relevant contextual cue is an implicit memory of action with a particular body part. To test this hypothesis we considered a task in which participants learned to control motion of a cursor under visuomotor rotation in two contexts: by moving their hand through motion of their shoulder and elbow, or through motion of their wrist. Use of these contextual cues led to three observations: First, in naive participants, learning in the wrist context was much faster than in the arm context. Second, generalization was asymmetric so that arm training benefited subsequent wrist training, but not vice versa. Third, in people who had prior wrist training, generalization from the arm to the wrist was blocked. That is, prior wrist training appeared to prevent both the interference and transfer that subsequent arm training should have caused. To explain the data, we posited that the learner collected statistics of contextual history: all upper arm movements also move the hand, but occasionally we move our hands without moving the upper arm. In a Bayesian framework, history of limb segment use strongly affects parameter uncertainty, which is a measure of the covariance of the contextual cues. This simple Bayesian prior dictated a generalization pattern that largely reproduced all three findings. For motor learning, generalization depends on context, which is determined by the statistics of how we have previously used the various parts of our limbs.     

No Evidence of the Ego-Depletion Effect across Task Characteristics and Individual Differences: A Pre-Registered Study

Ego-depletion, a psychological phenomenon in which participants are less able to engage in self-control after prior exertion of self-control, has become widely popular in the scientific community as well as in the media. However, considerable debate exists among researchers as to the nature of the ego-depletion effect, and growing evidence suggests the effect may not be as strong or robust as the extant literature suggests. We examined the robustness of the ego-depletion effect and aimed to maximize the likelihood of detecting the effect by using one of the most widely used depletion tasks (video-viewing attention control task) and by considering task characteristics and individual differences that potentially moderate the effect. We also sought to make our research plan transparent by pre-registering our hypotheses, procedure, and planned analyses prior to data collection. Contrary to the ego-depletion hypothesis, participants in the depletion condition did not perform worse than control participants on the subsequent self-control task, even after considering moderator variables. These findings add to a growing body of evidence suggesting ego-depletion is not a reliable phenomenon, though more research is needed that uses large sample sizes, considers moderator variables, and pre-registers prior to data collection.     

Development of size structure in tiger salamanders: the role of intraspecific interference

Cannibalism affects patterns of density-dependent mortality and may regulate population size. In many cases, rates of cannibalism depend on size structure, the frequency distribution of body sizes in the population, because cannibals can often only capture and consume smaller individuals. Size differences within single-age groups can be caused by a variety of factors. In this research we tested the hypothesis that size variation among larval tiger salamanders is due, in part, to interference interactions among individuals of different sizes. We found that size variation was greater when we raised larvae in groups rather than in isolation. This increase in size variation was due more to a relative deceleration of growth among smaller individuals rather than acceleration among larger individuals. We also found that smaller larvae had lower feeding rates than larger larvae when in groups, but not when isolated. Including spatial structure to limit physical interactions did not affect the size specificity of feeding rate, although it reduced feeding rates overall. We argue that these results are consistent with the hypothesis that larger larvae interfere, probably indirectly, with the feeding behavior of small individuals and this contributes to increases in size variation over time. We hypothesize that this indirect interference is caused by a behavioral response of smaller larvae to the risk of predation (cannibalism) by larger individuals. Received: 18 May 1998 / Accepted: 29 April 1999     

SWEET-HOME ICT technologies for the assessment of elderly subjects

Functional assessments are designed to ascertain a person's ability to perform activities of daily living (ADL) and provide valuable diagnostic as well as care-planning information. Currently, the gold standard for the assessment of functional ability involves clinical rating scales. However, scales are often limited in their ability to provide objective and sensitive information. In contrast, information and communication technologies (ICT) may overcome these limitations by capturing more fully the functional, as well as behavioral and cognitive disturbances associated with Alzheimer disease (AD). In this context, the ANR Tec San 2009 SWEET-HOME project aims at building an innovative framework for modeling ADL. The first result of the SWEET-HOME project has been the installation in a classical consultation setting of a specific room equipped with audio and video sensors. This leads to the following results: (1) physical activity recognition done by patients, (e.g., balance test, repeated transfers between sitting and standing): the monitoring system is able to detect the full set of activities with a detection rate varying from 96.9% to 100% (true positive rate); (2) activity of daily living: the monitoring system had an average sensitivity of 90% and an average precision of 83.51%. Using a functional score it is possible to differentiate AD patients from healthy controls; (3) acceptability of the system: results of the survey (all the 64 participants who accepted to be assessed using the system) indicated that the assessment has been perceived as pleasant (83%).     

Social learning of a novel foraging patch in families of free-living Florida scrub-jays

Free-living juvenile Florida scrub-jays, Aphelocoma coerulescens, learned to forage in a novel patch (the centre of a ring) when in proximity to other family members that foraged successfully. We were able to distinguish the contributions of social learning and of individual learning, and to show that social learning occurred. The foraging task required individual jays to dig for peanut bits (chopped fragments) buried in sand in the centre of a 33-cm plastic ring. Jays were trained in their family groups to perform the task during a summer season, and were allowed to perform the task in the presence of juveniles (aged 40-85 days) in later years. Jays living in 18 control families received partial exposure to the training situation, but received no exposure to the ring before being presented with the task in the presence of their young. Juveniles in 16 families with trained jays were able to witness demonstrations and to scrounge peanut pieces from the models as they completed the task. These 41 juveniles learned more of the task than the 33 juveniles in control families. Seven juvenile jays and two older, nonbreeding jays in the trained families completed the task at least once, whereas no jays in control families completed the task. A modified task that prevented snatching also prevented transmission of the complete task, although the 22 juveniles that observed the modified task learned more of the task than the 33 control juveniles. Further analysis indicated that demonstrations had their greatest effect in increasing the probability that juveniles would enter the ring. Copyright 2000 The Association for the Study of Animal Behaviour.     

Is the Cultural Transmission of Irrelevant Tool Actions in Adult Humans (Homo Sapiens) Best Explained as the Result of an Evolved Conformist Bias?

Background

Recent studies of social learning have revealed that adult humans are “over-imitators” who frequently reproduce a model''s causally irrelevant tool actions to the detriment of task efficiency. At present our knowledge of adult over-imitation is limited to the fact that adults do over-imitate, we know very little about the causes of this behavior. The current study aimed to provide novel insights into adult over-imitation by extending a paradigm recently used with human children to explore social aspects of over-imitation. In the child study observers saw two models demonstrate a tool-use task using the same inefficient approach, or two models demonstrate different approaches to the task (one inefficient and one efficient). The manipulation of social influence came in the testing phase where the observer completed the task in the presence of either an inefficient model or an efficient model.

Methodology/Principal Findings

We adapted the paradigm used in the child study to provide the first systematic exploration of factors which may lead to adult over-imitation including: 1) the presence of the model(s) during testing, 2) the presence of a competing efficient task demonstration, 3) the presence of a majority displaying the inefficient approach, and 4) the ‘removal’ of the experimental context during task completion. We show that the adult participants only over-imitated in conditions where the inefficient strategy was the majority approach witnessed. This tendency towards over-imitation was almost entirely eliminated when the participants interacted with the task when they believed the experiment to be complete.

Conclusions

Our results suggest that adult over-imitation is best explained as a result of an evolved ‘conformist bias’ argued to be crucial to the transmission of human cultural behavior and one which may be unique in the animal kingdom.     

Discrimination of Infant Isolation Calls by Female Greater Spear-Nosed Bats, Phyllostomus hastatus

In colonial species, recognition of offspring should be under strong selection. For accurate identification to occur offspring must emit individually distinctive signals and parents must be able to discriminate between signals. Female greater spear-nosed bats (Phyllostomus hastatus) roost in stable social groups and use infant vocalizations, termed isolation calls, to locate and identify their young. In this study, we investigate both the production and perception of isolation calls in P. hastatus. First, we measured acoustic features and found that after controlling for ontogenetic effects, sufficient variation exists between pups for isolation calls to function as individual signatures. Moreover, pups from the same social group emit calls with more similar spectral and spectro-temporal features than pups from different social groups, indicating that these features are likely heritable. We used psychoacoustic experiments in the laboratory to determine if adult females could discriminate between calls from pups in the same or different social group. Females discriminated between pups when faced with a template-matching task and their performance was correlated with the salience of spectral and spectro-temporal features. We found no difference in performance when females had to discriminate between pups from the same and different social groups. These results indicate that females should be able to accurately identify their young using isolation calls.     

Sometimes slower is better: slow-exploring birds are more sensitive to changes in a vocal discrimination task

Animal personality, defined as consistent individual differences across context and time, has attracted much recent research interest in the study of animal behaviour. More recently, this field has begun to examine how such variation arose and is maintained within populations. The habitat-dependent selection hypothesis, which posits that animals with differing personality types may fare better (i.e. have a fitness advantage) in different habitats, suggests one possible mechanism. In the current experiment, we tested whether slow- and fast-exploring black-capped chickadees (Poecile atricapillus), determined by performance in a novel environment exploration task, perform differentially when the demands of an acoustic operant discrimination (cognitive) task were altered following successful task acquisition. We found that slow-exploring birds learn to reverse previously learned natural category rules more quickly than faster exploring conspecifics. In accordance with the habitat-dependent selection hypothesis, and previous work with great tits (Parus major), a close relative of the black-capped chickadee, our results suggest that fast-exploring birds may perform better in stable, predictable environments where forming a routine is advantageous, while slow-exploring birds are favoured in unstable, unpredictable environments, where task demands often change. Our results also support a hypothesis derived from previous work with great tits; slow-exploring birds may be generally more flexible (i.e. able to modify their behaviour in accordance with changes in environmental stimuli) in some learning tasks.     

Always Gamble on an Empty Stomach: Hunger Is Associated with Advantageous Decision Making

Three experimental studies examined the counterintuitive hypothesis that hunger improves strategic decision making, arguing that people in a hot state are better able to make favorable decisions involving uncertain outcomes. Studies 1 and 2 demonstrated that participants with more hunger or greater appetite made more advantageous choices in the Iowa Gambling Task compared to sated participants or participants with a smaller appetite. Study 3 revealed that hungry participants were better able to appreciate future big rewards in a delay discounting task; and that, in spite of their perception of increased rewarding value of both food and monetary objects, hungry participants were not more inclined to take risks to get the object of their desire. Together, these studies for the first time provide evidence that hot states improve decision making under uncertain conditions, challenging the conventional conception of the detrimental role of impulsivity in decision making.