NCERT Book Class 11 Psychology The Bases of Human Behaviour

The Bases of Human Behaviour

Introduction

Human beings, the homo sapiens, are the most developed organisms among all creatures on this earth. Their ability to walk upright, larger brain size relative to body weight, and the proportion of specialised brain tissues make them distinct from other species. These features have evolved through millions of years and have enabled them to engage in several complex behaviours.

Scientists have attempted to study the relationship of complex human behaviour with the processes of the nervous system, particularly of the brain. They have tried to discover the neural basis of thoughts, feelings, and actions. By understanding the biological aspects of human beings, you will be able to appreciate how brain, environment and behaviour interact to generate unique forms of behaviour.

In this chapter, we begin with a general description of the nervous system in an evolutionary perspective. You will also study the structure and functions of the nervous system. You will learn about the endocrine system, and its influence on human behaviour. Later in this chapter, you will also study the notion of culture and show its relevance to the understanding of behaviour. This will be followed by an analysis of the processes of enculturation, socialisation, and acculturation.

EVOLUTIONARY PERSPECTIVE

You must have observed that people differ with respect to their physical and psychological characteristics. The uniqueness of individuals results from the interaction of their genetic endowments and environmental demands. In this world, there are millions of different species of organisms differing in a variety of ways. Biologists believe that these species werenot always like this; they have evolved to their present form from their pre-existing forms. It is estimated that the characteristics of modern human beings developed some 2,00,000 years ago as a result of their continuous interaction with the environment.

Evolution refers to gradual and orderly biological changes that result in a species from their pre-existing forms in response to the changing adaptational demands of their environment. Physiological as well as behavioural changes that occur due to the evolution process are so slow that they become visible after hundreds of generations.

Evolution occurs through the process of

natural selection. You know that members of each species vary greatly in their physical structure and behaviour. The traits or characteristics that are associated with high rate of survival and reproduction of those species are the most likely ones to be passed on to the next generations. When repeated generation after generation, natural selection leads to the evolution of new species that are more effectively adapted to their particular environment.

This is very similar to the selective breeding of horses or other animals these days. Breeders select the fittest and the fastest male and female horses from their stock, and promote them for selective breeding so that they can get the fittest horses. Fitness is the ability of an organism to survive and contribute its genes to the next generation.

Three important features of modern human beings differentiate them from their ancestors: (i) a bigger and developed brain with increased capacity for cognitive behaviours like perception, memory, reasoning, problem solving, and use of language for communication, (ii) ability to walk upright on  two legs, and (iii) a free hand with a workable opposing thumb. These features have been with us for several thousand years. Our behaviours are highly complex and more developed than those of other species because we have got a large and highly developed brain. Human brain development is evidenced by two facts. Firstly, the weight of  the brain is about 2.35 per cent of the totalbody weight, and it is the highest among all species (in elephant it is 0.2 per cent). Secondly, the human cerebrum is more evolved than other parts of the brain.

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