Testing brown lemurs (Eulemur fulvus) on the reverse-reward contingency task without a modified procedure

A common paradigm used to study inhibitory control is the reverse-reward contingency task in which the subject is presented with a choice between two different quantities of food and is rewarded with the non-chosen item. Most animals have problems inhibiting their impulsive choice towards the larger quantity, and need correction procedures to master the reverse-reward task. Recent studies have nonetheless shown that rhesus macaques and white crowned mangabeys were able to master the task without correction procedures after a large number of trials were applied.We previously demonstrated that, similar to other primates tested under the reverse-reward contingency task, lemurs initially showed an impulsive bias towards the larger quantity of food. But following introduction of a large-or-none contingency, all the subjects learned to reliably select the smaller quantity in order to gain access to the larger one. Here, we assessed the possibility that, similar to rhesus macaques and mangabeys, lemurs could master the reverse-reward task, without a modified procedure, by presenting a large number of trials. One of 5 subjects was able to master the task and then generalize performance to novel food arrays.     

The capacity of dogs to solve problems by operating with the empirical dimensions of figures]

An investigation was made into the dogs capacity for operating with empirical dimensions of figures, i.e. the animal's capacity for solving problems based on the fact that out of two figures a volumetric bait can be placed only in a volumetric figure and not in a flat one. In experiments using two methods (single and multiple presentations of figures, each time of a new pair), the dogs were incapable of solving the problems. They were able, however, to elaborate in the course of learning a visual differentiation of a volumetric figure from a flat one, which implies the formation of a generalization of the volume cue as the only invariant in all the pairs of figures. The investigation into operation with empirical dimensions of figures as one of the objective parameters in estimating elementary reasoning activity of animals indicates that by this criterion dogs range in the philogenetic series by far lower than the previously studied marmoset monkeys and dolphins.     

Humans can adopt optimal discounting strategy under real-time constraints

Critical to our many daily choices between larger delayed rewards, and smaller more immediate rewards, are the shape and the steepness of the function that discounts rewards with time. Although research in artificial intelligence favors exponential discounting in uncertain environments, studies with humans and animals have consistently shown hyperbolic discounting. We investigated how humans perform in a reward decision task with temporal constraints, in which each choice affects the time remaining for later trials, and in which the delays vary at each trial. We demonstrated that most of our subjects adopted exponential discounting in this experiment. Further, we confirmed analytically that exponential discounting, with a decay rate comparable to that used by our subjects, maximized the total reward gain in our task. Our results suggest that the particular shape and steepness of temporal discounting is determined by the task that the subject is facing, and question the notion of hyperbolic reward discounting as a universal principle.     

Male mate preference for large size overrides species recognition in allopatric flat lizards (<Emphasis Type="Italic"> Platysaurus broadleyi</Emphasis>)

Species recognition and mate preference both influence mate choice but can be in conflict with each other. In such cases the relative importance of the two functions depends on the costs of mating with heterospecifics and the frequency of such interactions. We tested whether male flat lizards (Platysaurus broadleyi) are able to discriminate between conspecific females and females of its allopatric sister species P. capensis. Given a simultaneous choice between equally sized females of both species, males courted conspecific females in 85% of trials. We then tested whether mate preference for large female body size can override species recognition. When offered a choice between a larger heterospecific female and a smaller conspecific, males showed no preference for conspecifics and courted larger heterospecific females in 58% of trials. Comparison of the two sets of trials showed a significant effect of female body size on male mate preference, supporting the hypothesis that mate quality can override species recognition.Communicated by K. Kotrschal     

Constituted through Conflict: Images of Community (and Nation) in Bulgarian Rural Ritual

Following the 20th anniversary of Benedict Anderson's Imagined Communities, this article extrapolates how attention to actual notions of community might redirect his important intervention. It suggests that locally and culturally specific ideas about collectivity shape the experience and expectations of national-level projections. To demonstrate this outcome the analysis focuses on Bulgarian mumming—spectacular winter rituals in which threatening masked figures transverse villages to banish evil and bring good fortune. While these rituals clearly reinforce social solidarity, they represent a local notion of community in which conflict, both intra-and interethnic, is elemental and constitutive. This image of community does not demand consensus or homogeneity when imagined on a national scale. Such variations in community notions may help explain the diversity of national experiences increasingly documented by ethnographers.     

Testing the cranial evolutionary allometric ‘rule’ in Galliformes

Recent comparative studies have indicated the existence of a common cranial evolutionary allometric (CREA) pattern in mammals and birds, in which smaller species have relatively smaller faces and bigger braincases than larger species. In these studies, cranial allometry was tested using a multivariate regression between shape (described using landmarks coordinates) and size (i.e. centroid size), after accounting for phylogenetic relatedness. Alternatively, cranial allometry can be determined by comparing the sizes of two anatomical parts using a bivariate regression analysis. In this analysis, a slope higher or lower than one indicates the existence of positive or negative allometry, respectively. Thus, in those species that support the CREA ‘rule’, positive allometry is expected for the association between face size and braincase size, which would indicate that larger species have disproportionally larger faces. In this study, I applied these two approaches to explore cranial allometry in 83 Galliformes (Aves, Galloanserae), ranging in mean body weight from 30 g to 2.5 kg. The multivariate regression between shape and centroid size revealed the existence of a significant allometric pattern resembling CREA, whereas the second analysis revealed a negative allometry for beak size and braincase size (i.e. contrary to the CREA ‘rule’, larger galliform species have disproportionally shorter beaks than smaller galliform species). This study suggests that the presence of CREA may be overestimated when using cranium size as the standard measurement.     

The Role of Sex-specific Plasticity in Shaping Sexual Dimorphism in a Long-lived Vertebrate,the Snapping Turtle <Emphasis Type="Italic">Chelydra serpentina</Emphasis>

Sex-specific plasticity, the differential response that the genome of males and females may have to different environments, is a mechanism that can affect the degree of sexual dimorphism. Two adaptive hypotheses have been proposed to explain how sex-specific plasticity affects the evolution of sexual size dimorphism. The adaptive canalization hypothesis states that the larger sex exhibits lesser plasticity compared to the smaller sex due to strong directional selection for a large body size, which penalizes individuals attaining sub-optimal body sizes. The condition-dependence hypothesis states that the larger sex exhibits greater plasticity than the smaller sex due to strong directional selection for a large body size favoring a greater sensitivity as an opportunistic mechanism for growth enhancement under favorable conditions. While the relationship between sex-specific plasticity and sexual dimorphism has been studied mainly in invertebrates, its role in long-lived vertebrates has received little attention. In this study we tested the predictions derived from these two hypotheses by comparing the plastic responses of body size and shape of males and females of the snapping turtle (Chelydra serpentina) raised under common garden conditions. Body size was plastic, sexually dimorphic, and the plasticity was also sex-specific, with males exhibiting greater body size plasticity relative to females. Because snapping turtle males are larger than females, sexual size dimorphism in this species appears to be driven by an increased plasticity of the larger sex over the smaller sex as predicted by the condition-dependent hypothesis. However, male body size was enhanced under relatively limited resources, in contrast to expectations from this model. Body shape was also plastic and sexually dimorphic, however no sex by environment interaction was found in this case. Instead, plasticity of sexual shape dimorphism seems to evolve in parallel for males and females as both sexes responded similarly to different environments.     

Physiological mechanisms underlying the control of meal size in Manduca sexta larvae

Abstract. Fifth stadium larvae of the tobacco hornworm, Manduca sexta (L.), ate larger meals than usual when they had been deprived of food for periods of time longer than the usual intermeal interval (c. 45 min). Meal size increased with time since the last meal until 180 min, when it was about 3 times normal. There was no evidence of a role for volumetric feedback from the gut in controlling meal size. Injections of a paraffin oil/wax mixture, or of petroleum jelly (Vaseline) into the foregut, midgut or rectum failed to decrease meal size. Cutting the recurrent nerve failed to alter meal size compared to sham-operated controls (although both groups took smaller meals than unoperated controls). By contrast, injections of an extract of soluble nutrients from the diet into the midgut inhibited feeding in some insects and reduced subsequent meal size in others. Appropriate controls showed that these effects were not due to the volumetric or osmotic effects of the injections. These results imply that nutrient feedback plays an important role in controlling meal size in Manduca caterpillars, while volumetric feedback is probably unimportant.     

Morphometric Analysis of Sunflower (<Emphasis Type="Italic">Helianthus annuus</Emphasis> L.) Achenes from Mexico and Eastern North America<Superscript>1</Superscript>

Morphometric Analysis of Sunflower ( Helianthus annuus L.) Achenes from Mexico and Eastern North America. Sunflower (Helianthus annuus L.) has played a major role in the evolution of agricultural systems in the Americas. The discovery of ancient domesticated remains from archaeological deposits in pre-Columbian Mexico offers new dimensions to widely accepted viewpoints on the domestication pattern of H. annuus. Although American sunflower populations north of Mexico have been examined extensively, Mexican indigenous domesticated landraces have not been studied in any detail. In this study, we morphologically assessed wild and domesticated sunflower achenes from Mexico and compared them to similar datasets from eastern North America. Additionally, we evaluated the utility of four computer-assisted shape measurements in discriminating between wild and domesticated sunflower achenes (fruits) and compared variation in achene size among modern wild and cultivated populations from both Mexico and the U.S. We found that, of the shape parameters tested, none were informative in distinguishing wild achenes from domesticated varieties. Subsequent size analysis, using conventional parameters of length, width, and thickness, showed that modern wild populations from Mexico had smaller achenes compared to modern populations from eastern North America. Domesticated achenes unearthed from Mexican archaeological sites, however, were significantly larger than the early domesticated specimens recovered from eastern North America. Our methodological results indicate that variation in archaeological sunflower achenes is better described by conventional size parameters rather than computerized shape analysis.     

Categorical Biases in Perceiving Spatial Relations

We investigate the effect of spatial categories on visual perception. In three experiments, participants made same/different judgments on pairs of simultaneously presented dot-cross configurations. For different trials, the position of the dot within each cross could differ with respect to either categorical spatial relations (the dots occupied different quadrants) or coordinate spatial relations (the dots occupied different positions within the same quadrant). The dot-cross configurations also varied in how readily the dot position could be lexicalized. In harder-to-name trials, crosses formed a “+” shape such that each quadrant was associated with two discrete lexicalized spatial categories (e.g., “above” and “left”). In easier-to-name trials, both crosses were rotated 45° to form an “×” shape such that quadrants were unambiguously associated with a single lexicalized spatial category (e.g., “above” or “left”). In Experiment 1, participants were more accurate when discriminating categorical information between easier-to-name categories and more accurate at discriminating coordinate spatial information within harder-to-name categories. Subsequent experiments attempted to down-regulate or up-regulate the involvement of language in task performance. Results from Experiment 2 (verbal interference) and Experiment 3 (verbal training) suggest that the observed spatial relation type-by-nameability interaction is resistant to online language manipulations previously shown to affect color and object-based perceptual processing. The results across all three experiments suggest that robust biases in the visual perception of spatial relations correlate with patterns of lexicalization, but do not appear to be modulated by language online.     

Realistic Weight Perception and Body Size Assessment in a Racially Diverse Community Sample of Dieters

Recently, a shift in obesity treatment away from emphasizing ideal weight loss goals to establishing realistic weight loss goals has been proposed; yet, what constitutes “realistic” weight loss for different populations is not clear. This study examined notions of realistic shape and weight as well as body size assessment in a large community-based sample of African-American, Asian, Hispanic, and white men and women. Participants were 1893 survey respondents who were all dieters and primarily overweight. Groups were compared on various variables of body image assessment using silhouette ratings. No significant race differences were found in silhouette ratings, nor in perceptions of realistic shape or reasonable weight loss. Realistic shape and weight ratings by both women and men were smaller than current shape and weight but larger than ideal shape and weight ratings. Compared with male dieters, female dieters considered greater weight loss to be realistic. Implications of the findings for the treatment of obesity are discussed.     

Neural Mechanisms Underlying the Cost of Task Switching: An ERP Study

Background

When switching from one task to a new one, reaction times are prolonged. This phenomenon is called switch cost (SC). Researchers have recently used several kinds of task-switching paradigms to uncover neural mechanisms underlying the SC. Task-set reconfiguration and passive dissipation of a previously relevant task-set have been reported to contribute to the cost of task switching.

Methodology/Principal Findings

An unpredictable cued task-switching paradigm was used, during which subjects were instructed to switch between a color and an orientation discrimination task. Electroencephalography (EEG) and behavioral measures were recorded in 14 subjects. Response-stimulus interval (RSI) and cue-stimulus interval (CSI) were manipulated with short and long intervals, respectively. Switch trials delayed reaction times (RTs) and increased error rates compared with repeat trials. The SC of RTs was smaller in the long CSI condition. For cue-locked waveforms, switch trials generated a larger parietal positive event-related potential (ERP), and a larger slow parietal positivity compared with repeat trials in the short and long CSI condition. Neural SC of cue-related ERP positivity was smaller in the long RSI condition. For stimulus-locked waveforms, a larger switch-related central negative ERP component was observed, and the neural SC of the ERP negativity was smaller in the long CSI. Results of standardized low resolution electromagnetic tomography (sLORETA) for both ERP positivity and negativity showed that switch trials evoked larger activation than repeat trials in dorsolateral prefrontal cortex (DLPFC) and posterior parietal cortex (PPC).

Conclusions/Significance

The results provide evidence that both RSI and CSI modulate the neural activities in the process of task-switching, but that these have a differential role during task-set reconfiguration and passive dissipation of a previously relevant task-set.     

Unabhängigkeit der bewertung zweier musterparameter von deren unterschiedlichkeitsgrad bei der Dressur

Bees were trained on a black disc (rewarded) against a smaller grey disc (unrewarded). Thus the bees had the choice of distinguishing between the two training figures by relying on the difference in size or on the difference in greyness or on both parameters. The aim of the present investigation was whether the relative weight of these parameters depended upon the differences in size and greyness presented during the training phase. 1. During the first two days of training the relative rating of these parameters changed in some, though not all individuals. In these cases the size of the discs rose in importance while the greyness was rated uniformly high (Fig. 3). Later, from the third day of training onwards the parameters were rated constantly. 2. Whenever size and greyness of the two training figures differed noticeably the bee relied on both parameters. The bee rated both parameters independently of the quantity of the differences in size and greyness presented during the training (Fig. 5). Thus the bee's analysis of the tested patterns cannot be attributed solely to the training paradigm, but seems to rely also on given (innate) “analyzers” (cf. Sutherland and Mackintosh, 1971). The type of training patterns only determines which “analyzers” influence the choice reaction. 3. The bee's “analyzer for size” had an influence on the choice reaction only if there was a noticeable size-difference between the training figures. The “analyzer for shades of grey”, however, strongly influenced the choice reactions also in those cases where the training figures showed no difference in greyness but only differences in size (Fig. 2).     

Influence of the Emotional Perception of a Signal on the Electroencephalographic Correlates of Creative Activity

Subjects were asked to invent as many definitions (ideas of a definition) of emotionally positive, emotionally negative, or neutral notions as possible using notions of other semantic fields. In the control task, the notions to be defined and to be used in definition were of the same or close semantic fields. The EEG was recorded during task performance. Significant differences in EEG local power (LS) and spatial synchronization (SS) were established in comparison of EEGs recorded during performance of creative tasks differing in complexity, complex creative tasks differing in emotional background (positive and negative), and tasks performed with or without emotional induction. Differences in LS and SS were most distinct in the medio- and posterotemporal areas of both hemispheres. Positive emotions increased LS and differently affected SS. Negative emotions predominantly increased SS. Analysis of self-reports of the subjects showed that both positive and negative induced emotions increased the fluency of association of notions from different semantic fields but decreased the originality of the ideas produced by a subject to define a notion.     

A lengthy solution to the optimal propagule size problem in the large-bodied South American freshwater turtle, <Emphasis Type="Italic">Podocnemis unifilis</Emphasis>

In oviparous vertebrates lacking parental care, resource allocation during reproduction is a major maternal effect that may enhance female fitness. In general, resource allocation strategies are expected to follow optimality models to solve the energy trade-offs between egg size and number. Such models predict that natural selection should optimize egg size while egg number is expected to vary with female size, thus maximizing offspring fitness and consequently, maternal fitness. Deviations from optimality predictions are commonly attributed to morphological constraints imposed by female size, such as reported for small-bodied turtle species. However, whether such anatomical constraints exist in smaller-bodied females within large-bodied clades remains unstudied. Here we tested whether resource allocation of the river turtle Podocnemis unifilis (a relatively smaller member of the large-bodied Podocnemididae) follows optimality theory, and found a pattern of egg elongation in smaller females that provides evidence of morphological constraints and of a reproductive trade-off with clutch size, whereas egg width supports the existence of an optimal egg size and no trade-off. Moreover, larger females laid larger clutches composed of rounder eggs, while smaller females laid fewer and relatively more elongated eggs. Elongated eggs from smaller females have larger volume relative to female size and to round eggs of equal width. We propose that elongated eggs represent a solution to a potential morphological constraint suffered by small females. Our results suggest that larger females may optimize fitness by increasing the number of eggs, while smaller females do so by producing larger eggs. Our data supports the notion that morphological constraints are likely more widespread than previously anticipated, such that they may not be exclusive of small-bodied lineages but may also exist in large-bodied lineages.     

You Do the Math: Coding of Bets and Outcomes in a Gambling Task in the Feedback-Related Negativity and P300 in Healthy Adults

The feedback-related negativity (FRN) is an event-related potential (ERP) component associated with processing of performance feedback, with more negative amplitudes for losses relative to wins. The amplitude of the FRN following near misses, i.e. the experience of coming close to winning, is between the amplitude elicited by losses and wins. In gambling, however, outcome value may not always be obvious since initially placed bets need to be taken into account when evaluating wins or losses. It is still unclear if initial bet size is reflected in the FRN or the later P300 component. The present study applied a virtual card gambling task to investigate the sensitivity of FRN and P300 to the manipulation of outcome magnitude as implemented through the presence or absence of initial bets, resulting in wins, losses or ambivalent outcomes, with the latter representing losses with and wins without bets. The FRN was larger for trials with bets compared to trials without bets. Wins were associated with a smaller FRN than losses or ambivalent outcomes, while losses and ambivalent outcomes did not differ. P300 amplitudes were larger for trials without bets, and wins were associated with a larger P300 than losses or ambivalent outcomes. Crucially, P300 amplitudes were also smaller for ambivalent outcomes compared to losses. Thus, the different dimensions determining outcome value appear to be integrated in early and late stages of feedback processing. However, only at later stages reflected in the P300 were ambivalent outcomes with and without bet clearly distinguished from other outcomes.     

Aggression and RHP in the Northern Swordtail Fish, Xiphophorus cortezi: The Relationship Between Size and Contest Dynamics in Male–Male Competition

Current theory predicts that contest outcome, as well as decisions on whether to initiate a contest, escalate during a contest or retreat are decided by asymmetries in resource holding potential (RHP) and/or expected payoffs between contestants. In this investigation, dyadic contests were staged between male swordtail fish (Xiphophorus cortezi) where individuals were paired based on cumulative fight records and were ranked at the end of the trials in order to approximate RHP. Size was the only asymmetry that I did not attempt to control for and as a result, I was able to determine the relationships between size, contest initiation, escalation and outcome. Individuals changed their contest initiation strategy based on their size relative to that of their opponents, and contrary to predictions, the smaller of the two males in each contest was more likely to initiate the conflict than was the larger male. However, the larger of the two males was more likely to win and standard length proved to be a moderate predictor of an individual's final rank. Regardless of size, initiators fared poorly, winning only 31% of the contests. In instances where the smaller males won the contests, they were no more likely to initiate the encounter than was the larger male. However, when small males did win, fights lasted longer, suggesting that in some cases smaller males may be able to outlast their opponents.     

Forming of the visual cognitive structures in the monkey conditioned-reflex behaviour: the dependence on the sensory information

In monkeys, changes in size and shape of figures led to a significant decrease of correct solutions in training and a considerable increase of refusals from solution of tasks as well as the time of their motor response. The invariance of differentiation in this case was achieved after additional training. The data obtained show that, based on the stimulus sensory processing in conditioned-reflex training, in the long-term memory some differentiating signs are formed: the cognitive structures (the functional neurophysiological mechanisms) maintaining the classification of visual images. With these structures, temporary conditioned connection will be established. Their formation will be determined by the type of sensory information and provided for by existence in the long-term memory of separate subsystems for spatial as well as non-spatial information.     

Egg size plasticity corresponding to maternal food conditions in an annual fish,Ayu <Emphasis Type="Italic">Plecoglossus altivelis</Emphasis>

The classic model of Smith and Fretwell predicts that the optimal egg size will vary according to the shape of the relationship between offspring size and offspring fitness, which may vary among environments. Adaptive significance of intrapopulation egg size variation was examined using Ayu (Plecoglossus altivelis). The species has an annual and migratory life history. Fish under controlled rearing conditions become sexually mature with a trend that smaller females produced larger eggs later in the season. Observed egg size variation was explained by the maternal specific growth rate, which was composed of maternal body size and growing period. Hatchlings from larger eggs had a larger notochord length, larger yolk-sac and grew faster. Such offspring traits provide general advantages of increased larval size, which confer competitive ability for assuring early survivorship. In conclusion, egg size plasticity in Ayu suggests higher offspring fitness through enhancement of their accessibility to food.