From past lectures.... behaviors are a manifestation of three basic things:

Genes

Environmental input

Neuronal networks (receptors, transmitters, and processors)

This raises several questions:

Given the behavioral repertoire of most animals, do we expect a separate circuit for each behavior or class of behaviors?

How do we explain why animals do not behave the same way towards the same stimulus.

 

Understanding how signals are organized and processed within neuronal networks (including the brain) provides further insight as to how complex behaviors are produced.

The hierarchy of behaviors: one "decision" or behavior sets the stage for others

Example: a female frog's response to stimuli

Three main points

Initial state may determine very different outcomes

Some environmental stimuli may be ignored depending on physiological state

Despite this strongly mechanistic process, we expect the eventual outcome to be an adaptive response.

 

Initial state is determined by various factors, most relating to condition and life history (age, sex, time since last meal, etc.)

Classic ethology characterized many of these conditions as producing "drives", "motivations", or "tendencies".

Examples: Hunger Drive, Sex Drive, Thirst Drive.

These drives are often associated with behaviors that strongly affect fitness

Evidence: Animals may go to more extremes when these "drives" are presumably strongest

 

Problem: "Drive Theory" does not explain the process, just gives it a name.

Also, a specific "drive" can almost always be subdivided into other drives.

 

Although definitions of "drive" may be inadequate, clearly there is an organization to neural circuitry that helps an individual meet certain biological goals.

 

The following two examples highlight how physiological condition feeds back to influence patterns of behavior.

 

The blowfly searching for food

 

The receptivity of a female Anolis lizard during a reproductive season

 

Now, consider the importance of only doing one thing at a time

What happens when more that one physiological state is considered (e.g. eat or have sex, walk or attack prey)?

 

Animals have the ability to sort these conflicts out, with many neuronal checks and balances

Example: the preying mantis - walking and grasping with legs, but not doing both at the same time.

Take home message: Neural inhibition allows for more complex ranges of behavior

 

The response should depend on the relationship between each state and an animals fitness

 

Often: Avoid death first, then get energy, then make babies.

Life history theory examines the relationship between fitness and either reproducing now or waiting to a later time. Obviously, the likelihood of surviving to the next breeding opportunity plays a critical role in determining an organism's "priorities".

 

This suggests many variations on basic hierarchy given above

 

In many cases, physical environmental factors determine the likelihood of surviving, getting energy, and finding mates.

 

For many animals, social cues also influence physiological state.

 

Example: Temperature + male signals = reproductive activity by female Anolis lizards

 

Example: House mice and the "Bruce effect".

 

When it has been studied, it is clear that most animals have a number of complicated feedback mechanisms built into their ability to detect certain aspects of the physical and social environment. Again, these are shaped by natural selection

Example: the reproductive behavior of white-crown sparrows