Honest signaling in mouse lemur vocalizations?

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.

Honest signaling in academic publishing

Academic journals provide a key quality-control mechanism in science. Yet, information asymmetries and conflicts of interests incentivize scientists to deceive journals about the quality of their research. How can honesty be ensured, despite incentives for deception? Here, we address this question by applying the theory of honest signaling to the publication process. Our models demonstrate that several mechanisms can ensure honest journal submission, including differential benefits, differential costs, and costs to resubmitting rejected papers. Without submission costs, scientists benefit from submitting all papers to high-ranking journals, unless papers can only be submitted a limited number of times. Counterintuitively, our analysis implies that inefficiencies in academic publishing (e.g., arbitrary formatting requirements, long review times) can serve a function by disincentivizing scientists from submitting low-quality work to high-ranking journals. Our models provide simple, powerful tools for understanding how to promote honest paper submission in academic publishing.

Special Issue: Consciousness science and its theories A possible evolutionary function of phenomenal conscious experience of pain

Evolutionary accounts of feelings, and in particular of negative affect and of pain, assume that creatures that feel and care about the outcomes of their behavior outperform those that do not in terms of their evolutionary fitness. Such accounts, however, can only work if feelings can be shown to contribute to fitness-influencing outcomes. Simply assuming that a learner that feels and cares about outcomes is more strongly motivated than one that does is not enough, if only because motivation can be tied directly to outcomes by incorporating an appropriate reward function, without leaving any apparent role to feelings (as it is done in state-of-the-art engineered systems based on reinforcement learning). Here, we propose a possible mechanism whereby pain contributes to fitness: an actor-critic functional architecture for reinforcement learning, in which pain reflects the costs imposed on actors in their bidding for control, so as to promote honest signaling and ultimately help the system optimize learning and future behavior.

Animal Communication

Among Darwin’s brilliant ideas was his (1871) conception of animal communication signals as adaptive characteristics of a species. The idea was subsequently taken up by the ethologists of Europe in the 1930s (Lorenz, Tinbergen, and von Frisch in particular) in their studies of animal signaling systems in nature. For many subsequent researchers, human language was the implicit model for an animal communication system. Although not expecting the same level of complexity, these researchers assumed that animal signals transmitted information from sender to receiver that was honest, and that benefitted them both. However, the honest signaling/mutual benefit view was challenged by new researchers steeped in the sociobiology and behavioral ecology movement of the 1960s. The emphasis on competition in this new field inspired these researchers to reconceive the animal signaling process as one in which the sender manipulates the receiver to the sender’s advantage. This view was challenged in turn when researchers recognized that the receiver was not a passive party in the interaction, but fully capable of manipulating the sender to its advantage. The communication interaction can be viewed as an arm’s race. The handicap principle—the idea that honesty in signaling can be maintained if signals are costly—is one way the receiver may gain an edge in this competition. Eventually, game theory considerations led to the development of a revised perspective in which signals evolve only when both the sender and the receiver benefit on average, and where signals are honest on average. Researchers examining a particular signaling system’s signals these days ask not are the signals honest, but how reliable are the signals.

Integration of intra- and inter-sexual selection signaling

Sexual selection can drive the evolution of dramatic morphological and behavioral signals. This selection acts on both specific components of signals and overall signals that combine multiple sources of information. By studying the structure and variability of signals and their components we can improve our understanding of how sexual selection operates. Signal integration can be understood through the lens of classical signaling hypotheses or more recently defined systems approaches. Using crickets (Acheta domesticus), we evaluated competing hypotheses about signal integration and how observed patterns of signal integration fit into both systems approaches and classic signaling hypotheses. We measured three call types of 127 male crickets multiple times for a total of 930 observations. We found evidence for an underlying integrated signaling syndrome from which both intra- and intersexual signals stemmed. This syndrome was also affected by mass, suggesting honest signaling in the species. The presence of an integrated syndrome demonstrates that intra- and intersexual signals are incorporated in a redundant signal strategy in Acheta domesticus. This support for honest and redundant signaling is also consistent with a systems framework description of signals as degenerate and functionally modular—demonstrating one way in which classic hypotheses can be integrated with modern systems approaches.

Honest signaling of cooperative intentions

Trust can transform conflicting interests into cooperation. But how can individuals know when to trust others? Here, I develop the theory that reputation building may signal cooperative intent, or “trustworthiness.” I model a simple representation of this theory in which individuals 1) optionally invest in a reputation by performing costly helpful behavior (“signaling”); 2) optionally use others’ reputations when choosing a partner; and 3) optionally cooperate with that partner. In evolutionary simulations, high levels of reputation building, of choosing partners based on reputation, and of cooperation within partnerships emerged. Costly helping behavior evolved into an honest signal of trustworthiness when it was adaptive for cooperators, relative to defectors, to invest in the long-term benefits of a reputation for helping. I show using game theory that this occurs when cooperators gain larger marginal benefits from investing in signaling than do defectors. This happens without the usual costly signaling assumption that individuals are of two “types,” which differ in quality. Signaling of trustworthiness may help explain phenomena such as philanthropy, pro-sociality, collective action, punishment, and advertising in humans and may be particularly applicable to courtship in other animals.

Energetic and physical limitations on the breaching performance of large whales

The considerable power needed for large whales to leap out of the water may represent the single most expensive burst maneuver found in nature. However, the mechanics and energetic costs associated with the breaching behaviors of large whales remain poorly understood. In this study we deployed whale-borne tags to measure the kinematics of breaching to test the hypothesis that these spectacular aerial displays are metabolically expensive. We found that breaching whales use variable underwater trajectories, and that high-emergence breaches are faster and require more energy than predatory lunges. The most expensive breaches approach the upper limits of vertebrate muscle performance, and the energetic cost of breaching is high enough that repeated breaching events may serve as honest signaling of body condition. Furthermore, the confluence of muscle contractile properties, hydrodynamics, and the high speeds required likely impose an upper limit to the body size and effectiveness of breaching whales.

Condition-dependent trade-offs maintain honest signaling: A laboratory experiment

How and why animals and humans signal reliably is a key issue in biology and social sciences. For many years the dominant paradigm in biology was the Handicap Principle. It claims a causal relationship between honesty and signal cost and thus predicts that honest signals have to be costly to produce. However, contrary to the Handicap Principle, game theoretical models predict that honest signaling is maintained by condition dependent signaling trade-offs and honest signals need not be costly at the equilibrium. Due to the difficulties of manipulating signal cost and signal trade-offs there is surprisingly little evidence to test these predictions either from biology or from social sciences. Here we conduct a human laboratory experiment with a two-factorial design to test the role of equilibrium signal cost vs. signalling trade-offs in the maintenance of honest communication. We have found that the trade-off condition has much higher influence on the reliability of communication than the equilibrium cost condition. The highest level of honesty was observed in the condition dependent trade-off condition as predicted by recent models. Negative production cost, i.e. fix benefit-contrary to the prediction of the Handicap Principle-promoted even higher level of honesty than the other type of costs under this condition.