Behavior

Behavior may be defined as the outwardly expressed course of action produced in organisms in response to stimuli from a given situation. Behavior is limited to those responses, which are directed to external environment. All living organisms exhibit a variety of forms of behavioral activity. The complexity of the nervous system and endocrine system is especially important in determining the behavior of a living system. In general, organisms with most complex biological systems exhibit the most complex behavior.

Biologists study behavior in the laboratory and in natural environment. Ethology is the study of behavior in natural environments from the point of view of adaptations.

Classification of Behavior

Behavior has two major groups

(a) Innate Behavior

(b) Learning Behavior

Innate Behavior

Part of every organism's behavior is innate. Innate behavior passes from parent to offspring. Like any other type of inherited characteristics in the members of a species, innate behavior is adaptive. It promotes survival and reproduction. Innate behavior patterns include

(1) Orientation

(2) Simple reflex

(3) Instincts

All plant behavior is innate.

(1) Orientation

 It includes taxes and kinesis.

(a) Taxes: A taxis (sing) or taxic response is a movement of the whole animal in response to an external directional stimulus. Taxic movements may be towards the stimulus (positive), away from the stimulus (negative) or at particular angle to the stimulus.

(b) Kinesis: A kinetic response is a non-directional movement response in which the rate of movement is related to the intensity of the stimulus and not the direction of the stimulus. For example, the direction of movement of the tentacles of Hydra in search of food is random and slow but if water fleas are placed close to the Hydra the rate of movement of tentacles increases.

(2) Simple Reflexes

In vertebrate, a simple reflex is an involuntary stereotyped response of a part of an organism to a given stimulus. In terms of behavior, simple spinal reflexes are either flexion responses, involving withdrawal of a limb from a painful stimulus or stretch responses, involving the balance and posture of the organism.

(3) Instincts

Instincts are complex, inborn, stereotyped behavior patterns of immediate adaptive survival value to the organism and are produced in response to sudden changes in the environment. Instinct can equip an animal with a series of responses. This is important for animals with short life spans and with little or no parental care. Charles Darwin (1859) was the first to propose an objective definition of instincts in terms of animal behavior. He treated instinct as complex reflexes made of units' compatible (capable of coexistence) with mechanisms of inheritance, and thus, a product of natural selection that had evolved with other aspects of life.

Digger Wasp

Example: The female digger wasp (Ammophila Adriaanse) lays eggs in the summer and dies. The underground eggs develop. The flies emerge from the pupae in the spring. She mates with the male wasp. Then she prepares a nest, hunts and kills caterpillars, stores the caterpillars in the nest, lays eggs on these caterpillars and then closes the nest. After laying eggs, the female dies. The young ones that come out of the eggs, start feeding on the killed caterpillars, stored by their mother before death.

Three Spined Stickleback

Courtship Behavior - Three Spined Stickleback

Courtship behavior is example of a complex instinct in animals. Courtship is a series of ordered stimuli and responses between male and female prior to mating. The three-spined stickleback fish has an elaborate courtship pattern. A male has a red area on the underside of his belly. This red area is a necessary stimulus to a female. It is called a releaser or sign stimuli because it sets off a chain of responses. Once a female recognizes the releaser, she follows the male to a nest, which was prepared by the male.

After the female enters the nest, the male stimulates her to lay eggs by pushing against her. After the female lays her eggs, she is driven from the nest. Then, the male deposits sperms over the eggs.

Courtship behaviors are adaptive, and have survival value. Courtship is a necessary series of reactions that cause the male and female to release their gametes so the species is reproduced. The selective responses to stimuli suggested that there must be some built-in mechanism by which sign stimuli were recognized. This mechanism came to be called the Innate Releasing Mechanism (IRM). The important aspect of this concept is that the mechanism is envisaged (considered) as being innate, that is, both the recognition of the sign stimulus and the resulting response to it, are inborn and characteristic of the species.

Learning Behavior

It can be changed. Unlike instinctive behavior, learning involves some choice of responses to a given stimulus. In addition, learning is not directly controlled by genes as instinctive behavior i.e. animals with the greatest intelligence or capacity for learning are those with a complex nervous system.

The lion cub is quite helpless. The mother feeds it until it can move. It watches the parents and copies them, e.g. capturing of prey. It may catch live prey at the age of six months. Its behavior and method of hunting will change throughout its life. It will change according to circumstances.

Tinbergen Experiment

The figure illustrates a classic Tinbergen Experiment. It deals with the nesting behavior in digger wasp, which built its nest in a small burrow in the ground. A female wasp will often excavate and care for four or five separate nests flying to each one daily, cleaning it, and bringing food to the single larva in the nest. To test his prediction that the female digger wasp uses landmarks to keep track of her nest Tinbergen (1) placed a circle of pinecones around a nest opening and waited for the mother wasp to return. When she did, he watched as she tended the nest. When she flew away, he (2) moved the pinecones a few feet to one side of the nest opening. The next time the wasp returned she flew to the centre of the pinecone circle instead of to the actual nest opening. This experiment indicated that the wasp did use landmarks, and that she could learn new ones to keep track of her nests. However, it also raised another question. Did the wasp respond to the pinecones themselves or to their circular arrangement? To answer this question, Tinbergen (3) arranged the pinecones in a triangle around the nest and made a circle of small stones off to one side of the nest opening. This time, the wasp flows to the stones demonstrating that she cued in on the arrangement of this landmark rather than the landmarks themselves.

Types of Learning Behaviors

Learning is a process which manifests (that can be easily seen by the eye or perceived the mind) itself by adaptive changes in individual behavior because of experience. Two important features of learning's are:

(a) Learning results in adaptive changes.

(b) Learning can be measured indirectly only as what has been remembered because of learning. Learning can be classified as:

(a)      Habituation

(b)      Latent learning

(c)      Conditional reflex type-1       

(d)      Insight learning

(e)      Conditional reflex type-2

(f)      Imprinting (trial and error)

a) Habituation

It is a torn of learning in which animals learn not to response to "frequently occurring" external stimuli that are essentially irrelevant. It is the simplest form of learning. Habituation does not involve acquisition of new responses but the loss of old ones, Habituation it adaptive.

Example: A spider will crawl quickly to the place in its web which moves as a fly becomes entangle a in the web. If the web is moved with a glass rod, the spider also rushes over the moving area. If it is repeated a second time, a third, fourth, fifth time and so forth, the spider becomes less responsive. Finally, it does not respond at all until it is left undisturbed for some time.

b) Conditional Reflex Type-1

Ivan Pavlov

Ivan Pavlov was a Russian scientist. He got the Nobel Prize in 1904. He is famous for his experiments on conditioning and learning.

Experiment of Ivan Pavlov

Experiment of Ivan Pavlov

In this original conditioning experiment, Pavlov restrained a hungry dog in a harness (gear, equipment) and presented small portions of food at regular intervals. When he signaled the delivery of food by preceding it with an external stimulus like the sound of a bell, the behavior of the dog toward the stimulus gradually changed. The animal began by orienting to the bell, licking its lips and salivating. When Pavlov recorded the salvation systematically by placing a small tube in the salivary duct and collecting the saliva, he found that the amount of saliva collected increased as the animal experienced pairing between the sound of the bell and food presentation. It appeared that the dog had learned and associated the bell with the food.

Pavlov referred to the bell as the conditional stimulus and to the food as the unconditional stimulus while salivation in response to the bell was called the conditioned response Note: though Pavlov, originally used the word “conditional" and unconditional this terminology was mistranslated at an early stage and the term conditioned was introduced. However, it is modem practice to return to Pavlov original terminology i.e., “conditional”.

(c) Trial and Error

This type of learning is called conditional reflex-2. The animal learns by chance and by repeating it. The difference between conditional reflexes 1 and 2 is that the former depends on a reflexive response to a stimulus whereas the later uses the promise of a positive reinforcement to trigger a voluntary action, such as pressing of lever.

Thorndike (1908) used various problem boxes in his pioneer experiments on learning.

Thorndike experiment on cat

Experiment

Depressing a lever cage can be opened from inside. A cat was placed inside the cage. The   cat tried hard to escape. It moved about restlessly. By chance it stepped on the lever (or latch), and the door opened, By second, third, fourth etc., chances the cat learned to open the cage by pressing the lever (or latch). As the animal teams by chance i.e. trial, so this type of learning has been named “trial and error learning”. In this type animal learns when it is “rewarded” in the form of food, escape etc. It is nowadays called instrumental learning, the correct response being “instrumental” in providing access to reward.

Latent Learning , rat experiment

(d) Latent Learning

It takes place when an animal actively seeks to find out more about its environment. Such simple behavior may be called curiosity, this exploratory learning needs no reward. Latent learning is "the association of indifferent stimuli or situations without patent reward". Biologically, latent learning is Important for an animal to prepare for far important changes In its environment.

Example: A rat was put in a maze (maze is a network of path), The rat explores through It sniffing into corners. Then the rat will return to its cage. Place some food at the upper most comer of the maze. Then put the rat. The rat because of its previous experience will find the food quickly (hen a rat that has been put without previous exploratory experience.

Advantage: Animal having latent learning has advantage over an animal that has not learned to explore and retrace its path, or that needs a reward to learn anything.

(e) Insight learning

Insight learning is a much more complex type of learning because it requires that an animal must respond correctly to a particular situation it has never met before. Animals capable of insight learning seems to practice a sort of mental trial and error process, analyzing the possibilities for the solution of a problem before actually setting out to tackle it.

Experiment of Kohler 

Experiment of Kohler on Chimpanzees

Kohler placed a chimpanzee in a cage containing several boxes having outreached hung bananas. The chimpanzee solved this problem by stacking the boxes so that it could climb on them to reach the bananas. No experience provided the chimpanzee with his "plan of attack”. Somehow, he was able to “think" out the fact that putting the boxes on top of each other would provide a means for reaching the bananas. He used insight to solve the problem. The chimpanzee formed a “concept” or idea. The chimpanzee's idea was that added height would allow him to reach the bananas. This type of behavior is in direct contrast to trial and error learning. Although both forms involve experience, insight or reasoning enables the animal to “path” other than randomly try several approaches. In fact insight learning is common only among primates i.e. humans, apes, monkeys and is quite rare among other animals.

(f) Imprinting

It is a type of learning in which just a single experience or few experiences have a long lasting effect in changing the animal’s behavior. In 1930 Konrad Lorenz originated the term imprinting to show how newly hatched goslings permanently regard as their mother, any moving creature they can follow. Imprinting takes place during the first few hours of a bird’s life and is no longer possible after that crucial early period has passed.

Konrad Lorenz  

Experiment of Konrad Lorenz

Experiment of Konrad Lorenz

Lorenz raised ducklings and goslings and allowed them to follow him as he walked along quacking. When he introduced the young birds to adult members of their own species, the ducklings and goslings ran from the adults and hurried back to him. Later in life, many of these imprinted birds paid little attention to members of their own species, preferring the companionship of human beings.