Human Perceptual and Phobic Biases for Snakes: A Review of the Experimental Evidence

In this paper I review the literature on the evolutionary origins of phobias and describe the current state of research on the neurobiology and developmental origins of ophidiophobia—fear of snakes. In doing so I compare experimental evidence related to evolutionary explanations for snake fears and phobias which are outlined in Seligman’s Preparedness Theory and Isbell’s Snake Detection Theory. These theories have been tested extensively using a variety of experimental paradigms aimed at determining the “innateness” of snake fears, the neural pathways involved in fear responses to snakes, and the perceptual biases associated with snake stimuli. However, in the vast majority of these experiments, the stimuli presented are photographs of snakes rather than the real thing. I argue that this point of methodology, while ironically supportive of the findings, is based on some assumptions about cognition and consciousness which run counter to neuroscience. In understanding human responses to snakes, we need to understand better the interplay between cognition and consciousness and how these represent a pluralism of mind in which perception is much more than we think.     

Daily Rhythms of Body Temperature in Acornys russatus: The Response to Chemical Signals Released by Acomys cahirinus

Two species of spiny mice of the genus Acomys—the golden spiny A. russaturs and the common spiny A. cuhirinus—are syrnpatnc in the and and hot parts of the Rift Valley in Israel. The coexistence of these two species is due to exclusion of A. russatus mice by A. cuhirinus mice from nocturnal activity. The aim of this research was to study if odor signals released by A. cahirinus mice can play a role in the exclusion of A. russatus mice. A. russatus mice with an implanted transmitter recording body temperature (T_b) were kept alone in a metabolic chamber under constant conditions of ambient temperature (27°C) and photoperiod (12 h light: 12 h dark). After 5 days of recording, chemical signals from an A. cuhirinus mouse were added through the air tube going into the metabolic chamber of the A. russatus mice. This treatment caused a shift of ～ 2 h inT_b daily rhythm of the naive tested A. russutus mice, whereas no shift was observed in A. russatus mice that had been kept in the same room with the A. cahirinus mouse before measurements. These results strongly support the idea that chemical signals released by A. cahirinus mice can entrain the T_b rhythms of A. russatus mice. Therefore, it may be assumed that the exclusion of A. russatus mice from nocturnal activity by A. cuhirinus mice could be achieved through the odor released by the latter.     

A Mathematical Model of the Stability Control of Human Thorax and Pelvis Movements During Walking

A mathematical model is developed to study the human thorax and pelvis movements in the frontal plane during normal walking. The model comprises of two-link base-excited inverted pendulums with one-degree of rotational freedom for each link. Since the linear motion of the pelvis has a significant effect on the upper body stability, this effect is included in the model by having a base point moving in the frontal plane in a general way. Furthermore, because the postural stability is the primary requirement of normal human walking, the control law is developed based on Lyapunov's stability theory, which guarantees the stability of the pendulum system around the up-right position. To evaluate the model, the simulation results, including the angular displacement of each link and the torque applied on each link, are compared with those from gait measurements. It is shown that the simulation results match those from gait measurements closely. These results suggest that the proposed model can provide a useful framework for analysis of postural control mechanisms.     

Energy Nonequipartition in a Sheared Granular Mixture

The kinetic granular temperatures of a binary granular mixture in simple shear flow are calculated by means of the Direct Simulation Monte Carlo method. The results show that the temperature ratio is clearly different from unity (as may be expected since the system is out of equilibrium) and strongly depends on the restitution coefficients as well as on the parameters of the mixture. The influence of the temperature differences on the rheological properties is also discussed. The results are compared with the theoretical predictions obtained from the Boltzmann kinetic theory by using a Sonine polynomial expansion. The comparison shows an excellent agreement over the range of parameters investigated.     

Calcitonin gene-related peptide and substance P in the pharynx and lung of the bullfrog,Rana catesbeiana

Indirect double immunofluorescence labelling in the pharynx and lung of the bullfrog, Rana catesbeiana, demonstrated the occurrence, distribution, and coexistence of two neuropeptides. In the pharynx, immunoreactive calcitonin gene-related peptide (CGRP) and substance P (SP) were localized in nerve fibers distributed within and just beneath the ciliated epithelium. In the lung, CGRP and SP were localized in nerve fibers in five principal locations: 1) within the smooth muscle layer in the interfaveolar septa; 2) in the luminal thickened edges of the septa; 3) around the pulmonary vasculature; 4) within, and 5) under the ciliated epithelium. Within the smooth muscle layer in the septa, luminal thickened septa, and around blood vessels, almost all fibers showed coexistence of CGRP and SP. Within and just beneath the ciliated epithelium in the thickened septa, all fibers showed coexistence of CGRP and SP. No immunoreactivity for vasoactive intestinal polypeptide, neuropeptide Y, galanin, somatostatin, FMRFamide, and leucine-and methionine-enkephalins was detected in the nerve fibers within the larynx and the lung. Together with our previous data, the present findings suggest that peptidergic mechanisms are involved in the regulation of amphibian respiratory systems throughout their life.     

Creating the conditions for peacemaking: theories of practice in ethnic conflict resolution

Establishing the conditions for effective intergroup peacemaking is a formidable task in severe ethnic conflicts. Conflict resolution practitioners argue that a critical first step is developing preconditions which convince competing groups that there are opponents to whom it is worth talking, that it is possible to create structural changes conducive to a stable peace, and that an agreement is possible which can meet each side's basic concerns and needs. This article compares six theories of practice of ethnic conflict resolution: community relations, principled negotiation; human needs; psychoanalytically rooted identity; intercultural miscommunications and conflict transformation, examining how each understands ethnic conflict; the goals it articulates; the effects of good practice on participants in interventions; the mechanisms by which the project achieves its impact; and the dynamics of transfer affecting the course of a wider conflict. It is argued that clearer articulation of these assumptions will improve both theory and practice in the search for settlements to severe ethnic conflict.     

Behavioral investigation of the coexistence of substance P,corticotropin releasing factor,and acetylcholinesterase in lateral dorsal tegmental neurons projecting to the medial frontal cortex of the rat

Colocalization of substance P (SP), corticotropin releasing factor (CRF), and acetylcholinesterase (AChE) was detected by retrograde tracing and immunocytochemical staining in the nucleus tegmentalis dorsalis lateralis (ntdl) projecting to the medial frontal cortex (MFC), septum, and thalamus of the rat. The histochemical results suggest that SP and CRF coexist within a subpopulation of ntdl cholinergic neurons that project to a number of forebrain regions including the MFC. Behavioral studies of the effects of SP, CRF, and the cholinergic agonist, carbachol, employed microinjections into the MFC of rats. SP and CRF did not elicit any behavioral effects when administered alone. Carbachol (1–5 μg/side) produced a stereotyped motor behavior, consisting of rapid forepaw treading while in an upright posture, resembling “boxing.” SP (1 μg/side) increased carbachol-induced “boxing.” CRF (1–10 ng/side) decreased carbachol-induced “boxing.” One possible functional significance of the coexistence of SP, CRF, and acetylcholinesterase, in neurons projecting to the medial frontal cortex in rats, appears to be a modulatory potentiation of cholinergic response by SP, and a modulatory inhibition of the cholinergic response by CRF.     

Simple rules for the coexistence and competitive dominance of plants mediated by mycorrhizal fungi

Mycorrhizal fungi have been demonstrated to be important in the makeup of plant communities. Likely, their most important role is in altering mineral nutrition of plants, which, in turn, is thought to be among the most important determinants of plant competitive ability. Using mathematical models we examine what role these fungi can play in determining the competitive outcome between two plants in competition for one mineral resource. Depending on different relationships between the benefit accrued to the plant and the fungi, the presence of mycorrhizal fungi can (i) have no impact on which plant wins in competition, (ii) change the order of competitive dominance or (iii) enable coexistence when compared with the system in the absence of mycorrhizal fungi. Furthermore, environmental conditions, such as light and nutrient levels, can determine if coexistence is possible. We describe the necessary biological trade‐offs for coexistence and experimental tests for these trade‐offs.     

Theorems on the invasion process in stage-structured populations with density-dependent dynamics

 Several theoretical results on evolution in stage-structured models with density-dependent dynamics are obtained. The first one concerns the invadable condition of mutant types when ‘density’ is considered as the weighted sum of the population densities at each stage. In the second and third results, it is shown that the invadability is equivalent to the increase of the weighted sum at equilibrium when certain conditions are satisfied. It is also shown that the sensitivity for the dominant eigenvalue is proportional to that for the weighted sum at equilibrium. Finally, a theorem on the coexistence of a wild and the mutant types is obtained and the condition for coexistence is discussed. A part of these results are the extended theorems of what Charlesworth (1971, 1980, 1994) has already obtained. Received: 26 October 1996