Signal detection: applying analysis methods from psychology to animal behaviour

Male crickets in poor condition engage in less same-sex sexual behavior

Same-sex sexual behavior (SSB) is widespread among animals and is often treated as an evolutionary anomaly or mistake. An alternative view is that SSB occurs because individuals have broader or more permissive "mating filters." A broader filter means directing courtship toward anything that resembles a potential mate, while a narrower filter means having stricter criteria about when to court. Broader filters help ensure animals do not miss out on mating opportunities. However, it may be advantageous for individuals to narrow their mating filters under some conditions, such as when the costs of courtship increase because courting individuals are in poor condition. We examined whether mating filters, and the expression of SSB, is condition dependent in the Pacific field cricket (Teleogryllus oceanicus). When males were in poor condition (because they were reared on a poor diet), they courted other males less. However, condition did not influence courtship toward females. This finding provides evidence that animals can decrease their expression of SSB by flexibly narrowing their mating filters when in poor condition. Our results demonstrate the benefits of a mating filters approach to studying SSB-rather than being a mistake or an anomaly in need of special explanation, SSB may be better viewed as a consequence of flexible, condition-dependent changes in mating behavior. Such an approach can be applied to other contexts where behavior is directed toward unintended targets. We emphasize that our results, like other studies of SSB in nonhuman animals, tell us nothing about sexual identities in humans.

The impact of task measurements on sequential dependence: a comparison between temporal reproduction and discrimination tasks

Decisions about a current stimulus are influenced by previously encountered stimuli, leading to sequential bias. However, the specific processing levels at which serial dependence emerges remain unclear. Despite considerable evidence pointing to contributions from perceptual and post-perceptual processes, as well as response carryover effects impacting subsequent judgments, research into how different task measurements affect sequential dependencies is limited. To address this gap, the present study investigated the role of task type in shaping sequential effects in time perception, employing a random-dot kinematogram (RDK) in a post-cue paradigm. Participants had to remember both the duration and the direction of the RDK movement and perform the task based on a post-cue, which was equally likely to be direction or duration. To delineate the task type, we employed the temporal bisection task in Experiment 1 and the duration reproduction task in Experiment 2. Both experiments revealed a significant sequential bias: durations were perceived as longer following longer previous durations, and vice versa. Intriguingly, the sequential effect was enhanced in the reproduction task following the same reproduction task (Experiment 2), but did not show significant variation by the task type in the bisection task (Experiment 1). Moreover, comparable response carryover effects were observed across two experiments. We argue that the differential impacts of task types on sequential dependence lies in the involvement of memory reactivation process in the decision stage, while the post-decision response carryover effect may reflect the assimilation by subjective, rather than objective, durations, potentially linking to the sticky pacemaker rate and/or decisional inertia.

Determining the efficacy of visual inspections at detecting non-biosecurity-compliant goods

Examination of imported commodities by trained inspectors searching for pest organisms is a common practice that phytosanitary regulatory agencies use to mitigate biosecurity risks along trade pathways. To investigate the effects of target size and color on the efficacy of these visual assessments, we affixed square decals to polystyrene models of mandarins. Sample units of 100 model fruit containing up to 10 marked models were examined by inspectors. Six sizes in six shades of brown were tested across two prevalence levels. The experiment consisted of five inspection rounds where 11 inspectors examined 77 sample units within an allocated time. The probability that decals were detected increased with mark size and color contrast. Smaller, low-contrast marks were mainly missed. The prevalence rate did not affect the detectability. Through the experiment, the false-positive rate dropped from 6% to 3%, whereas false-negative rates were constant throughout. Large, dark targets were readily found with a mean recall of >90%, whereas small, pale marks had a mean recall of 9%. Increased experience made inspectors more competent at recognizing decals, reducing the false positive rate. However, constant false-negative rates indicate that experience did not prevent inspectors from overlooking targets they could not perceive.

Honesty, reliability, and information content of floral signals

Plants advertise their presence by displaying attractive flowers, which pollinators use to locate a floral reward. Understanding how floral traits scale with reward status lies at the heart of pollination biology, because it connects the different interests of plants and pollinators. Studies on plant phenotype-reward associations often use different terms and concepts, which limits developing a broader synthesis. Here, we present a framework with definitions of the key aspects of plant phenotype-reward associations and provide measures to quantify them across different species and studies. We first distinguish between cues and signals, which are often used interchangeably, but have different meanings and are subject to different selective pressures. We then define honesty, reliability, and information content of floral cues/signals and provide ways to quantify them. Finally, we discuss the ecological and evolutionary factors that determine flower phenotype-reward associations, how context-dependent and temporally variable they are, and highlight promising research directions.

The evolution of eavesdropping on heterospecific alarm calls: Relevance, reliability, and personal information

Interceptive eavesdropping on the alarm calls of heterospecifics provides crucial information about predators. Previous research suggests predator discrimination, call relevance, reliability, and reception explain when eavesdropping will evolve. However, there has been no quantitative analysis to scrutinize these principles, or how they interact. We develop a mathematical framework that formalizes the study of the key principles thought to select for eavesdropping. Interceptive eavesdropping appears to be greatly affected by the threat faced by caller and eavesdropper, as well as presence of informational noise affecting the detection of calls and predators. Accordingly, our model uses signal detection theory to examine when selection will favor alarm calling by a sender species and fleeing by an eavesdropping receiver species. We find eavesdropping is most strongly selected when (1) the receiver faces substantial threats, (2) species are ecologically similar, (3) senders often correctly discriminate threats, (4) receivers often correctly perceive calls, and (5) the receiver's personal discrimination of threats is poor. Furthermore, we find (6) that very high predation levels can select against eavesdropping because prey cannot continuously flee and must conserve energy. Reliability of heterospecific calls for identifying threats is thought to be important in selecting for eavesdropping. Consequently, we formally define reliability, showing its connection to specificity and sensitivity, clarifying how these quantities can be measured. We find that high call relevance, due to similar vulnerability to predators between species, strongly favors eavesdropping. This is because senders trade-off false alarms and missed predator detections in a way that is also favorable for the eavesdropper, by producing less of the costlier error. Unexpectedly, highly relevant calls increase the total number of combined errors and so have lower reliability. Expectedly, when noise greatly affects personally gathered cues to threats, but not heterospecific calls or detection of predators, eavesdropping is favored.

How honey bees make fast and accurate decisions

Honey bee ecology demands they make both rapid and accurate assessments of which flowers are most likely to offer them nectar or pollen. To understand the mechanisms of honey bee decision-making, we examined their speed and accuracy of both flower acceptance and rejection decisions. We used a controlled flight arena that varied both the likelihood of a stimulus offering reward and punishment and the quality of evidence for stimuli. We found that the sophistication of honey bee decision-making rivalled that reported for primates. Their decisions were sensitive to both the quality and reliability of evidence. Acceptance responses had higher accuracy than rejection responses and were more sensitive to changes in available evidence and reward likelihood. Fast acceptances were more likely to be correct than slower acceptances; a phenomenon also seen in primates and indicative that the evidence threshold for a decision changes dynamically with sampling time. To investigate the minimally sufficient circuitry required for these decision-making capacities, we developed a novel model of decision-making. Our model can be mapped to known pathways in the insect brain and is neurobiologically plausible. Our model proposes a system for robust autonomous decision-making with potential application in robotics.

Rethinking same-sex sexual behaviour: male field crickets have broad mating filters

Same-sex sexual behaviour (SSB) occurs in many animals and is often treated as an anomaly requiring special explanation. One common explanation for SSB is mistaken identity. However, animals make similar 'mistakes' in other contexts-such as attempting to mate with immature individuals or inanimate objects. Framing such behaviours as 'mistakes' risks misinterpreting how animals make flexible mating decisions. Here we make a case for an alternative approach to thinking about SSB by instead considering an individual's mating filter. A broad filter means directing courtship toward anything that resembles a potential mate, whilst a narrow filter means only courting with receptive targets. We illustrate this approach by examining the mating filters of male Pacific field crickets (Teleogryllus oceanicus). We find that males engage in SSB but also misdirect courtship toward juveniles (but not plastic crickets). This finding suggests that SSB is not an anomaly and is better considered alongside other misdirected behaviours. We argue that by viewing misdirected behaviours through the lens of mating filters rather than as 'mistakes' we can build a more nuanced understanding of reproductive behaviour and begin to determine when having a broader mating filter can be advantageous.