Identification of analytic signals

This paper is devoted to the identification of analytic signals and to find a solution to the following problem. Given a realization of an analytic signal, it is necessary to find the analytic function by which the signal is described. The proposed approach to this problem is based on relatively simple relationships existing between many analytic signals and their respective derivatives. These relationships are closely related to the properties of the dynamic systems which generate the signals under investigation. Simple identification procedures are described and tested by means of computer simulation.     

Social learning and social transmission of foraging information in Norway rats (Rattus norvegicus)

Adult male Norway rats were tested in a first experiment to see whether foraging efficiency could be improved by social learning. Observers were placed in one of four conditions in which they were paired with demonstrators that either had or had not been previously trained to dig for buried carrot pieces, and in which the demonstrators either did or did not have carrot buried in the experimental enclosure. Observers in the group with trained demonstrators that did have carrot pieces buried in the experimental area during the observation period subsequently unearthed more buried carrot, did so more rapidly, and were generally more active than were the observers in the other three groups. In a second experiment, chains of transmission were established by allowing each observer to act as a demonstrator for the next naive observer. Enhanced levels of digging behavior were maintained across eight transmission episodes in three transmission groups relative to a no-transmission control group, the performance levels becoming stable after five transmission episodes at a level significantly above that of the control group. The study demonstrates that social learning and transmission mechanisms exist which might result in the diffusion of certain patterns of behavior through populations of Norway rats.     

A New Approach to Electrical Engineering Laboratories

A short analysis of the purposes and achievements of electrical engineering laboratories is given. As a result of this analysis, the conclusion is drawn that laboratories, as presently conceived, fail to accomplish their objectives. The new approach proposed is to limit the objectives as well as the laboratory time, which would result in an advanced electrical measurements course with an associated laboratory to demonstrate the lecture material.     

Simulation of modulated signals

A new formulation for the simulation of modulated signals based on a generalized structure is presented. In this approach a modulated signal is characterized in terms of a time-varying system whose differential equation is simulated. Algorithms presented in the paper may also be used to track signal parameters such as the envelope and the carrier. This concept is illustrated by several algorithms of AM and FM simulators.     

Social transmission of food preferences among norway rats by marking of food sites and by gustatory contact

Three experiments were conducted to investigate the social learning and transmission of food preferences by excretory marking among adult male Norway rats. The experiments extend our earlier findings that rats prefer to eat from a food bowl marked by the excretory deposits of conspecifics and that this mechanism can result in the communication and social learning of food preferences (Laland & Plotkin, 1991). Here we investigate whether a tradition of food and food site preferences can become established by these means. Experiment 1 established that the residual cues deposited by rats lose their powers of communication as “markers” of food sites over a 72-h period. Experiment 2 showed that while a socially enhanced preference for one flavored diet could be transmitted from one animal to the next along a chain, it was unstable for an alternative diet. This suggests that social transmission may be more stable when it reinforces a prior preference than when it conflicts with one. In Experiment 3, the stability of socially transmitted food preferences was bolstered by the addition of a second process for the communication of diet preferences-namely, gustatory cues on the demonstrator’s breath. This finding suggests that when a socially transmitted trait is mediated by more than one process, the processes may interact, and the diffusion is likely to be more stable.