Jeffrey C. Schank

Pseudoreplication is a pseudoproblem.

Pseudoreplication is one of the most influential methodological issues in ecological and animal behavior research today. At its inception, the idea of pseudoreplication highlighted important concerns about the design and analysis of experiments in ecology. The doctrine purported to provide a unified view of experimental design and analysis, wherein precise criteria could be used to assess manuscripts and research proposals for acceptance or rejection. Few methodological doctrines have had as much impact as pseudoreplication, yet there has been very little critical analysis of it. In this paper, the authors extend the growing criticism of the concept of pseudoreplication. The authors argue that the core ideas behind pseudoreplication are based on a misunderstanding of statistical independence, the nature of control groups in science, and contexts of statistical inference. The authors also highlight how other areas of research have found and responded to similar issues in the design and analysis of experiments through the use of more advanced statistical methods. Ultimately, there are no universal criteria for accepting or rejecting experimental research; all research must be judged on its own merits.

Do Norway rats (Rattus norvegicus) synchronize their estrous cycles

Estrous synchrony was tested using 10 pairs of sibling female rats (Rattus norvegicus). A Monte Carlo bootstrap simulation was used to construct random control groups to avoid previous statistical errors and to test for significance when there are irregular cycles. The 10 pairs of females did not exhibit estrous synchrony. The effect of cycle irregularity on the limits of synchrony was analyzed using an equation that the related degree of cycle regularity to the degree of synchrony. This equation significantly predicted the limits of synchrony: cycle irregularity limits both the maximum and minimum degree of synchrony that can occur between two females. Finally, simulations of the expected levels of synchrony in groups of five rats were compared to the original study on estrous synchrony. The simulations indicated that the results of the original study were consistent with chance levels of synchrony. It is concluded that there is no evidence that Norway rats synchronize their estrous cycles. Evolutionary implications are discussed.

Women Do Not Synchronize Their Menstrual Cycles

It is widely believed that women who live together or who are close friends synchronize their menstrual cycles. We reexamined this phenomenon in two ways. First, we collected data on menstrual cycles from 186 Chinese women living in dorms for over a year. We found that women living in groups did not synchronize their cycles. Second, we reviewed the first study reporting menstrual synchrony. We found that group synchrony in that study was at the level of chance. We then show that cycle variability produces convergences and subsequent divergences of cycle onsets and may explain perceptions of synchrony.

Menstrual-cycle synchrony: Problems and new directions for research.

Since M. K. McClintock (1971) published the 1st study on menstrual synchrony among women, a number of other studies have also reported synchrony using a variety of methods. The most recent reports of synchrony come from A. Weller, L. Weller, and colleagues, and their findings of synchrony have been getting stronger (by their own account). In this article, the author analyzes their new methodology and presents 2 simulation studies that demonstrate how biases and errors can produce synchrony as an artifact. Two mutually reinforcing categories of errors are identified: (a) errors in calculating the expected mean onset difference between cycles when there is cycle variability and (b) errors that may result from allowing participants to fill out menstrual-cycle-onset calendars, including recall biases and the mutual exchange of information. It is suggested that synchrony may be a biological state to be avoided and that cycle variability may facilitate female mate choice.

Recognition of partially concealed leopards by wild bonnet macaques (Macaca radiata): The role of the spotted coat

Wild bonnet macaques (Macaca radiata) have been shown to recognize models of leopards (Panthera pardus), based on their configuration and spotted yellow coat. This study examined whether bonnet macaques could recognize the spotted and dark melanic morph when partially concealed by vegetation. Seven troops were studied at two sites in southern India, the Mudumalai Wildlife Sanctuary and the Kalakad-Mundanthurai Tiger Reserve. The forequarters and hindquarters of the two leopard morphs were presented from behind thick vegetation to individuals at feeding stations 25 m away. Flight reaction times and frequency of flight were obtained from video for only those individuals who oriented towards the models prior to hearing alarm calls. Bonnet macaques exhibited faster reaction times and greater frequency of flight after looking at the spotted morphs forequarter than after looking at either its spotted hindquarter or the dark morphs forequarter. The hindquarter of the dark morph was ignored completely. Artificial neural network modeling examined the perceptual aspects of leopard face recognition and the role of spots as camouflage. When spots were integrated into the pattern recognition process via network training, these spots contributed to leopard face recognition. When networks were not trained with spots, spots did not act as camouflage by disrupting facial features.

Increased Costs of Cooperation Help Cooperators in the Long Run

It has long been proposed that cooperation should increase in harsh environments, but this claim still lacks theoretical underpinnings. We modeled a scenario in which benefiting from altruistic behavior was essential to survival and reproduction. We used a spatial agent-based model to represent mutual cooperation enforced by environmental adversity. We studied two factors, the cost of unreciprocated cooperation and the environmental cost of living, which highlight a conflict between the short- and long-term rewards of cooperation. In the long run, cooperation is favored because only groups with a sufficient number of cooperators will survive. In the short run, however, harsh environmental costs increase the advantage of defectors in cooperator-defector interactions because the loss of resources leads to death. Our analysis sheds new light on the evolution of cooperation via interdependence and illustrates how selfish groups can incur short-term benefits at the cost of their eventual demise. We demonstrate how harsh environments select for cooperative phenotypes and suggest an explanation for the adoption of cooperative breeding strategies in human evolution. We also highlight the importance of variable population size and the role of socio-spatial organization in harsh environments.

Rat pups and random robots generate similar self-organized and intentional behavior

Biorobotic research continually demonstrates that behavior and cognition can be the emergent products of (1) embodied agents that are (2) dynamically embedded within an environment and (3) equipped with simple sensorimotor rules. Thigmotaxis is an orientation response to contact manifested in infant rats by wall following, corner burrowing, and group aggregation. Orientation responses have been long thought to be mediated only by sensory or central processes. Here we show that a random control architecture in a morphologically similar robot embedded in a scaled environment can reproduce thigmotaxic behaviors seen in infant rats. We conclude that (1) and (2) may play a larger role than previously thought in the generation of complex behaviors.

A Biorobotic Investigation of Norway Rat Pups (Rattus norvegicus) in an Arena

Biorobotics research typically focuses on simulating specific aspects of animal biomechanics, sensory systems, and computational abilities. We have developed a novel methodology for integrating the study of biorobotics and animal behavior. We describe several metrics for characterizing and comparing rat pup and robot behavior without presupposing behavioral goal states. In the rat pup and robot experiments, we found that when 10-day-old Norway rats (Rattus Norvegicus) are placed in an arena, they typically follow walls to a single corner and stay there. However, our thigmotaxic robots followed walls but typically circumnavigated the entire arena, contacting all corners, and exhibiting asymmetric corner behavior. After observing the latter behavior in robots, we found that rat pups also exhibited asymmetric corner behavior. Thus, our robotic experiments, while not quantitatively matching pup behavior, led to the discovery of a previously unrecognized pattern of behavior in rat pups. This illustrates the value of models in leading to discovery of new patterns of behavior in the system modeled. Our results also show that simple thigmotaxic architectures alone may not explain pup behavior in an arena.

Beyond reductionism: refocusing on the individual with individual-based modeling

A s a psychologist, my research focuses on the behavior of individual organisms. Such research often requires the integration of causes at multiple levels of organization to explain, predict, and control behavior (e.g., lower levels include genetic, physiological, hormonal, and neurological causes; upper levels include, group, social, and ecological causes of behavior). A question of fundamental importance is whether focusing on the individual is more than a disciplinary perspective. Do individual organisms hold a special place in our understanding of the world? If so, how can we hope to integrate information from multiple levels of organization into a deeper understanding of the complex behavior of individual organisms? In this essay, I argue that individual organisms do hold a special place in our world. My starting point is the precept that individual organisms are complex systems that are intractable to reductionistic explanation. This does not imply that JEFFREY C. SCHANK

Menstrual-cycle variability and measurement: further cause for doubt

This paper critically examines Weller and Wellers preferred last month only method for measuring synchrony. Within-woman and between-women menstrual-cycle variability are distinguished. If there is within-woman cycle variability, synchrony requires a process of entrainment. Between-women cycle variability precludes synchrony between rhythms that are not integer multiples of each other. The assumptions of Weller and Wellers last month only measurement model are tested by computer simulation under conditions of cycle variability. It is demonstrated that these assumptions are biased towards finding synchrony when it does not exist and that the degree of error is an increasing function of cycle variability. Indeed, the error uncovered quantitatively predicts the peculiar skew in their data distributions. Synchrony is almost impossible when there is cycle variability and finding synchrony may be an indicator of a methodological artifact rather than a phenomenon.