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It has been argued that men's hunting in many forager groups is not, primarily, a means of family provisioning but is a costly way of signaling otherwise cryptic qualities related to hunting ability. Much literature concerning the signaling value of hunting draws links to Zahavi's handicap principle and the costly signaling literature in zoology. However, although nominally grounded in the same theoretical paradigm, these literatures have evolved separately. Here I review honest signaling theory in both hunter-gatherer studies and zoology and highlight three issues with the costly signaling literature in hunter-gather studies: (a) an overemphasis on the demonstration of realized costs, which are neither necessary nor sufficient to diagnose costly signaling; (b) a lack of clear predictions about what specific qualities hunting actually signals; and (c) an insufficient focus on the broadcast effectiveness of hunting and its value as a heuristics for signal recipients. Rather than signaling hunting prowess, hunting might instead facilitate reputation-building., (© 2019 Wiley Periodicals, Inc.)

Humans frequently perform extravagant and seemingly costly behaviors, such as widely sharing hunted resources, erecting conspicuous monumental structures, and performing dramatic acts of religious devotion. Evolutionary anthropologists and archeologists have used signaling theory to explain the function of such displays, drawing inspiration from behavioral ecology, economics, and the social sciences. While signaling theory is broadly aimed at explaining honest communication, it has come to be strongly associated with the handicap principle, which proposes that such costly extravagance is in fact an adaptation for signal reliability. Most empirical studies of signaling theory have focused on obviously costly acts, and consequently anthropologists have likely overlooked a wide range of signals that also promote reliable communication. Here, we build on recent developments in signaling theory and animal communication, developing an updated framework that highlights the diversity of signal contents, costs, contexts, and reliability mechanisms present within human signaling systems. By broadening the perspective of signaling theory in human systems, we strive to identify promising areas for further empirical and theoretical work., (© 2019 Wiley Periodicals, Inc.)

Animal vocalizations may provide information about a sender's condition or motivational state and, hence, mediate social interactions. In this study, we examined whether vocalizations of gray mouse lemurs (Microcebus murinus) emitted in aggressive contexts (grunts, tsaks) co-vary with physical condition, which would underly and indicate honest signaling. We recorded calls from captive individuals that were subjected to a caloric restricted (CR) or ad libitum (AL) diet, assuming that individuals on an ad libitum dietary regime were in better condition. We analyzed 828 grunts produced by seven CR and nine AL individuals and 270 tsaks by eight CR and five AL individuals. Grunts consisted of two separate elements, with the 1st element having more energy in higher frequencies than the 2nd element. Body mass correlated negatively with acoustic features of grunts, and heavier individuals produced lower-frequency grunts. Acoustic features of grunts did not differ between sexes. Acoustic features of tsaks were predicted by neither body mass nor sex. However, tsaks produced by AL individuals were noisier than those of CR individuals. Hence, manipulation of body condition via dietary regimes affected acoustic features of calls given during aggression in different ways: acoustic features of grunts varied according to the rule of acoustic allometry, and can be considered as honest signals. Acoustic features of tsaks, however, varied according to motivational structural rules. Longitudinal studies are now indicated to examine whether intra-individual changes in body mass are also reflected in the acoustic structure of calls, allowing callers to signal more flexible variation in condition. [ABSTRACT FROM AUTHOR]

Signal reliability is a major focus of animal communication research. Aggressive signals are ideal for measuring signal reliability because the signal referent - attack or no attack - can be measured unambiguously. Signals of aggressive intent occur at elevated rates in aggressive contexts, predict subsequent aggression by the signaler, and elicit appropriate responses from receivers. We tested the 'predictive criterion' in smoothbilled anis, Crotophaga ani, by broadcasting one of two playback types ('ahnee' calls only or 'ahnee + hoot' calls), presenting a taxidermic mount, and observing the animals' behavior. Based on the hypotheses that 'hoot' calls and 'throat-inflation' displays signal aggressive intent, we predicted that they would be associated with attack, and that signaling rate would increase over the time period leading up to an attack. Indeed, both hoots and throat-inflation displays reliably predicted attack. The second prediction, that signaling rate increases in the time leading up to attack, was strongly supported for throat-inflation displays, which increased over the pre-attack period in both treatments. Hoots increased over the pre-attack period in ahnee playbacks but not in ahnee + hoot playbacks. Hierarchical signaling systems are characterized by early, lessreliable predictors of attack, and later, more reliable predictors of attack. During both natural and simulated interactions, the more-reliable throatinflation display tended to precede the less-reliable hoot call, suggesting that this signaling system is not hierarchical. In a comparison of 11 putative signals of aggressive intent in birds, the throat-inflation display had the second highest mutual information (reduction in uncertainty) among visual signals and non-passerine signals while hoots had below-average mutual information. Natural observations indicate that both hoots and throat-inflation displays occur in the context of aggressive between-group encounters, and hoots also occur during within-group interactions. Throat-inflation displays appear to be reliable indicators of aggressive intent, but the function of hoot calls is less clear. [ABSTRACT FROM AUTHOR]

In many plant species, larger flowers offer larger or higher quality rewards to visitors, and flower visitors preferentially visit these larger, more rewarding flowers. Limited evidence suggests that plants in which flower size provides more reliable information about reward value have higher reproductive success than plants in which flower size offers less reliable information. We tested whether bumblebees could learn to respond to flower size when it was an informative reward cue while simultaneously learning not to respond to it when it was not informative. We also tested whether bees would develop a preference for a flower type that provided reward cues over one that did not. Bees were allowed to forage on an artificial array containing 2 flower types, each with a unique color and scent. In the informative flower type, large flowers contained sucrose rewards, whereas small flowers contained quinine solution (a deterrent). In the uninformative flower type, both flower sizes were equally likely to contain sucrose or quinine. Bees learned to prefer large flowers in the informative flower type and to be indifferent to flower size in the uninformative type. However, contrary to expectations, bees did not develop a preference for the informative type. These results suggest that although bees may benefit from floral cues that give information about rewards, plants offering these cues may not receive more flower visits than plants that do not. [ABSTRACT FROM AUTHOR]

According to signaling theory and a large body of supporting evidence, males across many taxa produce courtship signals that honestly advertise their quality. The cost of producing or performing these signals maintains signal honesty, such that females are typically able to choose the best males by selecting those that produce the loudest, brightest, longest, or otherwise highest-intensity signals, using signal strength as a measure of quality. Set against this background, human flirting behavior, characterized by its frequent subtlety or covertness, is mysterious. Here we propose that the explanation for subtle and ambiguous signals in human courtship lies in socially imposed costs that (a) vary with social context and (b) are amplified by the unusual ways in which language makes all interactions potentially public. Flirting is a class of courtship signaling that conveys the signaler' s intentions and desirability to the intended receiver while minimizing the costs that would accompany an overt courtship attempt. This proposal explains humans' taxonomically unusual courtship displays and generates a number of novel predictions for both humans and non-human social animals. Individuals who are courting should vary the intensity of their signals to suit the level of risk attached to the particular social configuration, and receivers may assess this flexible matching of signal to context as an indicator of the signaler's broader behavioral flexibility and social intelligence. [ABSTRACT FROM AUTHOR]

The most commonly cited mechanism by which biological signals are kept honest is Zahavi’s (1975) ‘handicap principle’. This suggests that individuals must pay a high price to give their own signals to maintain honesty. Recently, a number of criticisms of this idea have been published. This manuscript clarifies, reiterates, and develops some of these arguments. I emphasize that measuring the costs individuals pay to give their own signal is not a useful approach for experimentalists.The honesty of animal communication has long been disputed and continues to be largely associated with the “handicap principle,” in which strategic costs are paid by signalers in order to maintain signal honesty. Recently, several manuscripts have forcefully made the point that costly signaling models do not require handicaps (realized signal costs) to be paid by signalers. The aim of the present manuscript is to reiterate, clarify, and develop some of those ideas. Although the message that handicaps are not necessary for honest signaling seems to have been readily accepted, the point that handicaps are also not sufficient for honest signaling has been less well understood by the communication community. I argue that the central separation should not be between “handicaps” and “other” mechanisms such as “indices” and “punishment of cheaters.” Indices, for example, are in fact a trivial exemplar of costly signaling, in which the cost functions associated with exhibiting a greater level of signal of signal expression are simply infinite. I advocate that the essential distinction is between circumstances where there is alignment of interest between signaler and receiver and those where there is not. I reenforce the view that the current focus on measuring the realized costs of signals (“handicaps”) is misplaced, as without further constraints the costly signaling paradigm makes no predictions about whether honest signalers pay strategic costs for giving their own signals. Rather, it only predicts potential costs for individuals giving dishonest signals—costs that are often not paid in an honest system. [ABSTRACT FROM PUBLISHER]