Thomas S. Ray

Open problems in artificial life

This article lists fourteen open problems in artificial life, each of which is a grand challenge requiring a major advance on a fundamental issue for its solution. Each problem is briefly explained, and, where deemed helpful, some promising paths to its solution are indicated.

Automated evolutionary design, robustness, and adaptation of sidewinding locomotion of a simulated snake-like robot

Inspired by the efficient method of locomotion of the rattlesnake Crotalus cerastes, the objective of this work is automatic design through genetic programming (GP) of the fastest possible (sidewinding) locomotion of simulated limbless, wheelless snake-like robot (Snakebot). The realism of simulation is ensured by employing the Open Dynamics Engine (ODE), which facilitates implementation of all physical forces, resulting from the actuators, joints constrains, frictions, gravity, and collisions. Reduction of the search space of the GP is achieved by representation of Snakebot as a system comprising identical morphological segments and by automatic definition of code fragments, shared among (and expressing the correlation between) the evolved dynamics of the vertical and horizontal turning angles of the actuators of Snakebot. Empirically obtained results demonstrate the emergence of sidewinding locomotion from relatively simple motion patterns of morphological segments. Robustness of the sidewinding Snakebot, which is considered to be the ability to retain its velocity when situated in an unanticipated environment, is illustrated by the ease with which Snakebot overcomes various types of obstacles such as a pile of or burial under boxes, rugged terrain, and small walls. The ability of Snakebot to adapt to partial damage by gradually improving its velocity characteristics is discussed. Discovering compensatory locomotion traits, Snakebot recovers completely from single damage and recovers a major extent of its original velocity when more significant damage is inflicted. Exploring the opportunity for automatic design and adaptation of a simulated artifact, this work could be considered as a step toward building real Snakebots, which are able to perform robustly in difficult environments.

Psychedelics and the Human Receptorome

We currently understand the mental effects of psychedelics to be caused by agonism or partial agonism of 5-HT2A (and possibly 5-HT2C) receptors, and we understand that psychedelic drugs, especially phenylalkylamines, are fairly selective for these two receptors. This manuscript is a reference work on the receptor affinity pharmacology of psychedelic drugs. New data is presented on the affinity of twenty-five psychedelic drugs at fifty-one receptors, transporters, and ion channels, assayed by the National Institute of Mental Health – Psychoactive Drug Screening Program (NIMH-PDSP). In addition, comparable data gathered from the literature on ten additional drugs is also presented (mostly assayed by the NIMH-PDSP). A new method is introduced for normalizing affinity (Ki) data that factors out potency so that the multi-receptor affinity profiles of different drugs can be directly compared and contrasted. The method is then used to compare the thirty-five drugs in graphical and tabular form. It is shown that psychedelic drugs, especially phenylalkylamines, are not as selective as generally believed, interacting with forty-two of forty-nine broadly assayed sites. The thirty-five drugs of the study have very diverse patterns of interaction with different classes of receptors, emphasizing eighteen different receptors. This diversity of receptor interaction may underlie the qualitative diversity of these drugs. It should be possible to use this diverse set of drugs as probes into the roles played by the various receptor systems in the human mind.

Host Tree Location Behavior of a Tropical Vine (Monstera gigantea) by Skototropism

Although still about 30 percent too lowfor population stability, productivity of California brown pelicans at their two northern colonies has improved significantly since 1971. Numbers of adults breeding probably reflect food supplies and recruitment from more successful colonies to the south, but improvingfledging rates (up to 0.9 young per nest in 1974) reflect better egg survival and improving eggshell condition, with declining DDE contamination in anchovies, their majorfood source.

Evolution, complexity, entropy and artificial reality

Abstract The process of Darwinian evolution by natural selection was inoculated into four artificial worlds (virtual computers). These systems were used for a comparative study of the rates, degrees and patterns of evolutionary optimizations, showing that many features of the evolutionary process are sensitive to the structure of the underlying genetic language. Some specific examples of the evolution of increasingly complex structures are described. In addition a measure of entropy (diversity) of the evolving ecological community over time was used to study the relationship between evolution and entropy.

Early experience as a variable in mate selection

Summary An experiment has been presented using pigeons as subjects in which early experience with parent colour (black-white) was varied systematically. Parent colour has been shown to influence later mate choice by males but not by females. Alternative explanations offered were: Mate choice in pigeons is predominately a male-dominate process, mate choice in female pigeons may not be a function of early experience, or mate choice in female pigeons may be based on early experience with parental characteristics other than colour.

Foraging behaviour in tropical herbaceous climbers (Araceae)

Climbing aroids grow through the forest, and demonstrate changes in their shoot developmental patterns associated with the changes in microhabitat resulting from displacement of the apex. Through allometric development or metamorphosis, shoots are able to shift growth forms: by altering their mobility, meristems of climbing species may disperse from their site of germination on the ground to their site of maturation on tree trunks, and then become sessile. Some species have the ability to become mobile again should environmental conditions change (...)

Aesthetically Evolved Virtual Pets

The author applies aesthetic, emotional and empathetic selection to a derivative of Karl Simss Evolved Virtual Creatures. The resulting Creatures can be beautiful or strange and provoke strong reactions in human observers. The author posits that it may therefore be possible to evolve virtual pets to which humans can form strong emotional bonds.

Measures of evolvability in Tierra

A variety of indices are tested for their ability to discriminate periods of evolution from periods of stasis in Tierra. Measures which recognize the emergence of new adaptations are favored. To remove artifacts, the shadow method of Bedau is used. A promising measure tracks the positive derivative of Simpsons index.

Evolution of side-winding locomotion of simulated limbless, wheelless robots

Inspired by the efficient method of locomotion of the rattlesnake Crotalus cerastes, the objective of this work was the automatic design through genetic programming of the fastest possible, side-winding locomotion of simulated limbless, wheelless artifacts. The realism of the simulation is ensured by employing open dynamics engine (ODE), which allows accounting for all the physical forces resulting from the actuators (muscles), friction, gravity, collisions, and joint constraints. The empirically obtained results demonstrate that the complex side-winding locomotion emerges from relatively simple motion patterns of morphological segments (vertebrae). The robustness of automatically evolved locomotion is verified by (i) the reasonable performance degradation when partial damage to the artifact is inflicted, and (ii) the ability to tackle obstacles. Contributing to the better understanding of the unique, side-winding locomotion, this work could be considered as a step toward building real limbless, wheelless robots, featuring unique engineering characteristics, which are able to perform robustly in difficult environments.