Psychology 351 – Animal Behavior

Alcock, Chapter 3 – The Development of Behavior
Summary by Chris Mattox

Introduction
- Development is an interactive process in which genetic information interacts with changing internal and external environments in ways that assemble an organism with special properties and abilities.

The Interactive Theory of Development
- Genotype : many thousands of genes.
- Phenotype : measurable characteristics.
  • The information in the bee’s many thousands of genes (bee’s genotype) must respond to the environment in ways that influence the development of her measurable characteristics (bee’s phenotype), which include the proximate mechanisms underlying her behavior, such as the nervous system, and her behavioral traits as well.
- Microarray Technology : makes it possible to look for relative levels of activity in a large set of genes by detecting the products (messenger RNAs) made when those genes have “turned on.”

The Nature or Nurture Fallacy
- Bee foraging behavior cannot be purely “genetically determined” (Nature) because the behavior is the product of literally thousands of gene-environment interactions (Nurture), all of which are required to construct the bee’s brain and the rest of its body.
  • Gene Robinson : DNA is both inherited and environmentally responsive.

Behavioral Development Requires Both Genes and Environment
- The DNA (gene) contribution to behavioral development is evident in the ability to learn, since learned behaviors are so often said to be environmentally determined, even though they are not.
- The constraints on learning are a consequence of specialized features of the brain, which in turn arise through the interplay between information-rich genes and the environment.
- Imprinting : a young animal’s early social interactions, usually with its parents, lead to it’s learning such things as what constitutes an appropriate sexual partner.

What Causes Individuals to Develop Differently?
- One of the facts of development is that members of the same species frequently differ in their behavior.

Environmental Differences and Behavioral Differences
- Environmental differences are important whenever members of a species differ in a learned behavior.
  • Example : differences among individuals in their odor “environment” translate into learned differences in their behavior.

Genetic Differences and Behavioral Differences
- Many differences in behavioral phenotypes have been linked to genetic differences among individuals, which makes sense given the interactive, dual-factor nature of development.

Single-Gene Effects on Development
- A difference in even a single gene product can lead to many divergences in the gene-environment interactions occurring in different individuals, which may translate into large behavioral differences between them.
- The search for genetic variation that affects human behavioral development has led some researchers to one particular part of the brain, the lateral frontal cortex, which is known to contribute to human intelligence.
  • Humans have (23) pairs of chromosomes in all.

Evolution and Behavioral Development
- If there is a genetic variation that leads to behavioral variation in animal populations today, then surely the same applied to populations in the past.
  • The alleles that contribute to the development of reproductively superior phenotypes will become more common over time, while the other alleles will eventually disappear.

What do Artificial Selection Experiments Tell Us about Behavioral Evolution?
- Artificial Selection Experiments : researchers get to determine which behavioral phenotypes will reproduce and which will not.
  • If the phenotypic differences among the test subjects are hereditary, then over time, the particular allele(s) associated with the phenotypes that are allowed to reproduce should become more common in the experimental population, while the frequency of alternative alleles linked to less “successful” traits should decrease.

Adaptive Feature of Behavioral Development
- Considerable phenotypic variation characterizes most species.
- The developmental process often appears to be capable of generating a typical or average outcome even in the face of shortfalls in genetic information, such as those caused by mutation, or deficits in environmental inputs of the sort that one would think would be important to normal development.

Development Homeostasis : Protecting Development Against Disruption
- Developmental Homeostasis : a process by which animals have the ability to develop more or less normally, despite defective genes and deficient environments.


The Adaptive Value of Development Switch Mechanisms
- Polyphenisms : to identify the environmental cues that activate the developmental mechanisms that steer development down one or another pathway (the process of “canalization”), so that an individual acquires one or another distinct phenotype, rather than any variety of intermediates between the alternative forms.

The Adaptive Value of Learning
- Learning : the adaptive modification of behavior based on experience.
  • Learning can be considered a polyphenism of sorts.
- Brood Parasites : parasites that lay their eggs in other birds’ nests.
- Operant Conditioning : an animal learns to associate a voluntary action with the consequences that follow that action.