Excerpted from: Personality: A Behavioral Analysis by Robert W. Lundin, 1964, p 201.
Ch. 8 The Influence of
Biological and Early
Environmental Conditions
on Personality Development
8 - 11
EACH TIME AN ORGANISM learns a new response, personality is developing. In the preceding chapters, we considered the basic principles governing the acquisition of behavior. In subsequent chapters we shall consider supplemental principles. An approach to personality that stresses the processes in learning is a study of psychological development. We share with Freud the conviction that the best understanding of personality is to be had by taking the longitudinal approach. In the use of the case history, he asked his patients to recall the events of their past, including the significant experiences of their infancy, childhood, and adolescence. The reverse procedure is also possible by observing a young organism and noting the modifications of behavior which take place under many changing stimulus conditions. Any currently observable response or chain of responses is a function of the many variables that have affected the individual in his history of conditioning.
The viewpoint of this book has stressed and will continue to emphasize behavioral changes that take place as an organism interacts with the stimuli in his environment. In this chapter we shall limit ourselves to two special problems in personality development: (1) the biological limitations and potentialities for specific learning and (2) the effects of early environmental stimulation on later personality development.
HEREDITY
In Chapter 2 we made clear that heredity is not the cause of behavior. We do not inherit intelligence, special abilities, or personality characteristics. Heredity merely sets the limits within which an organism can respond. Between species and within species a great variation exists in the kinds of structures that have been inherited. In all species where reproduction is bisexual, the organism starts life as a uniting of two cells, one from each parent. Within this new cell unit are chromosomes (colored bodies) which occur in pairs, the two members of each pair having certain likenesses in appearance and function. In the union of the two original cells, one chromosome in each pair comes from both parents. The number of chromosomes in each cell differs from one species to another, but they are ordinarily the same in number within any one species. Within these chromosomes are the genes, the basic carriers of the hereditary traits.
Heredity, then, consists of the specific genes an individual receives from each parent at the moment of conception. Ordinarily, the genes are so minute that they are not visible even under a high-powered microscope. After the union of the two parent cells, a process of cell division takes place and continues until billions of cells, which make up the mature organism, have developed. All cells in the body thus possess the same heredity. The fact that some develop into eye cells, others into skin cells, and others into hair cells, and so forth depends on the special environment of the cells. This includes gravity, pressure, availability of oxygen, other chemicals that act differentially upon the cells, and the influence of each cell upon other cells.
At sexual maturity, a different kind of cell division occurs in which special cells for reproduction are formed. There is a reduction in the amount of division, since the chromosomes in each division have been reduced to half the original number. In this kind of division each reproductive cell can receive a different combination of chromosomes. When conception takes place by the uniting of the mother and father reproductive cells (ova and spermatozoon), the full number of chromosomes is restored and continues through subsequent cell division.
Even a simple biological characteristic depends on a number of genes. These interact in determining a particular structure that the parents transmit to the offspring. The traits that are passed on are only those that the parents themselves have received. The cells that eventually determine the mature structures, through a complex interaction, may represent a vast assortment of genes derived from the entire ancestry of the individual. It is possible to have a characteristic quite unlike one's parents but one that is still due to heredity. Brown-eyed parents usually produce brown-eyed children, but an occasional blue-eyed one is possible. The Mendelian laws explain quite clearly how this is possible. Some traits are dominant and others recessive, so that the presence of brown or blue eyes depends on the combination of genes inherited from both parents, which eventually determines the color.
The genes operate only in determining the structure of an individual. The growth of the structure progresses through an interaction with the environment. Early theorists supposed the possibility of the exclusive influence of heredity in determining a specific characteristic. However, in every developing structure there is both the influence of heredity and environment. An illustration of this interaction effect in determining a specific structure is seen in the fruit fly Drosophila, which has been extensively studied by geneticists. The number of facets in the eyes of the fruit fly differ in various types, depending on the particular gene constitution of each. However, the temperature at which the larvae are kept also influences the number of facets that will develop.
ENVIRONMENT
Environment has been used to refer to many things. We speak of the prenatal environment consisting of the diet, nutrition, glandular secretions, and other conditions of the mother which affect the growing fetus. The lasting influence of this environment is shown in the experimentally produced "monsters." Siamese-type twin fish can be developed by artificially subjecting the eggs to slower development, low temperatures, insufficient oxygen, or ultraviolet rays.1 Likewise, by the application of various chemicals, "two-headed" tadpoles can be produced. We are also familiar with the studies conducted to show the effects of radiation on prenatal development. Such exposure during the embryonic stage of growth results in a number of abnormalities, including changes in size and shape of the head and other parts of the body.2
Biologists also speak of intercellular environment, which consists of the surrounding cells in which each individual cell develops. These surrounding cells can influence the special way a designated cell grows. There is also intracellular environment. The genes within a cell are surrounded by a substance known as cytoplasm. Geneticists have suggested that these genes act as enzymes, inducing chemical changes in the cytoplasm. The action of a particular gene has different effects, depending on the specific chemical composition of a certain cell. Each gene also operates in an environment of other genes within any one cell.
Psychologists speak of the behavioral environment, a rather inclusive concept referring to current stimuli with which an organism interacts and to his earlier history of stimulation. Kantor3 suggests environment to be the sum total of stimulation a person has received from conception until death. Since the stimuli in an organism's environment (discriminative, reinforcing, and so forth) and the responses he makes to these stimuli are difficult to separate in his developmental history, Kantor proposes the concept of reactional biography, which constitutes the sum total of responses an organism has made to stimuli up to any particular stage in his development. It is his total life history of interacting with stimuli. This conception of environment not only includes the ordinary notion of present environment as stimuli but the past environment as well, since at any point in the development of an organism, the present responding is going to be a function of both. The concept of behavioral environment is not merely limited to objects in one's physical surroundings, for unless they act as stimuli, they will not exert any influence on his behavior.
Stimuli have different kinds of functions, depending on the relationships that exist between them and the responses an organism makes. There are eliciting stimuli found in respondent behavior. These can, if appropriate, "pull out" a response with or without prior conditioning, depending on their properties. (Salivation can occur on presentation of meat or the ringing of a bell if the appropriate stimulus association has developed.) We have frequently mentioned reinforcing stimuli which strengthen or weaken a response when they are presented or withdrawn. Discriminative stimuli set the occasion for an organism to respond or not to respond, according to the contingencies of reinforcement presented or withheld. Furthermore the secondary or conditioned reinforcing stimuli take on the function of a primary reinforcer through prior association with it. In the next section we shall discuss aversive stimuli, which are really not classified as special stimuli because their functions are also involved in primary and secondary reinforcement and discrimination. However, their effects on the responses tend to be the opposite of positive reinforcement. Those stimuli, then, both present and in the past history of the organism, that exert and have exerted an influence on its behavior (whether they be primary or conditioned, internal or external) constitute what we call the organism's psychological or behavioral environment.
BIOLOGICAL LIMITATIONS AND POTENTIALITIES
In speaking of limitations or potentialities, we are referring to opposite sides of the same coin. Certain structures can act as an advantage in learning some behavior or a disadvantage in acquiring other kinds of behavior. For example, inheriting two hands with four fingers and the opposed thumb on each is an advantage or structural potentiality for acquiring many kinds of manipulatory behavior. An absence or a defect in structure acts as a disadvantage and limits the possibilities of acquiring certain behaviors. Birds, lacking hand structures, cannot acquire many manipulatory behaviors, but having wings, can locomote in a manner unavailable to most mammals.
1. Hereditary Structures. The nature and development of bodily structures limit in some cases the possibility of behavior acquisition. The cat cannot learn to fly nor can the dog learn to climb a tree. The fact that humans have hands, vocal mechanisms, an upright posture, and a nervous system more complex than lower forms acts as a potentiality for the development of behavior not found among some other species. On the other hand, birds can see better, dogs can smell better, and monkeys can climb better than man because of structural advantages. The presence of a structure is a necessary but not a sufficient condition for behavioral acquisition. It does not assure a response. If no bars ever existed in the rat's environment, he would not learn to press them, although he has the structure that allows the possibility of this response. At the human level, the structural equipment of most persons allows a tremendous and almost limitless variety of behavioral possibilities. These structures are inherited, but the behavior is not. The structure merely acts as a limitation or potentiality within which behavior can or cannot be acquired, depending on the environmental contingencies.
2. Structural Defects. An individual may possess structural limitations that can be due either to heredity, accident, or disease. These last two conditions are, in the strict sense, environmental. The child with cerebral palsy is limited because of brain damage before birth in the acquisition of certain coordinated and skilled movements. He has been the victim of an environmental accident in the same sense that a man is blinded by fire. Often, following epidemic encephalitis (sleeping sickness), a child (or adult) is left mentally deficient after recovery from the immediate effects of the virus. Because of cerebral inflammation, his brain has been left damaged, thus limiting to some degree the kinds of behavior he can emit or will be able to learn in the future. Many forms of structural abnormalities leading to peculiar development and deficiency are the result of environmental accident, disease, insufficient nutrition, drugs, and poisons to which the fetus was subjected in its prenatal development.
Structural defects can also be inherited. Thyroid deficiency has been fairly well established as operating in a disorder known as cretinism. The child's condition is readily diagnosed by his stunted growth, coarse, thick skin, underdeveloped genitalia; and protruding abdomen. If defective genes were contributing to the inadequate thyroid development, the disorder would be, in this sense, inherited. From a point of view of behavior, the physical weaknesses have limited the possibility of the cretin's learning many responses, some intellectual in character, which are typical of the normal child. Another clearly identifiable disorder which acts as a limiter in behavior acquisition is a condition known as phenylpyruvic oligophrenia. The disorder is typified by the presence of phenylpyruvic acid in the urine because of the inability of the liver to manufacture an enzyme to utilize it. Geneticists believe that the condition depends on the presence of a simple recessive gene. The individual has very limited ability and is severely retarded mentally as a result. He often cannot learn to talk or to control his bladder or bowel movements. The heredity condition in this unusual case has placed a severe limitation on the amount and kinds of behavior that can be acquired.
Heredity does not cause behavior or lack of it. Neither do accidents or disease cause mental deficiency. In both cases the biological limitations and disadvantages have limited the acquisition of behavior through structures of the body. By structure we mean any organic, somatic, or psysiognomic condition. Included are anatomical, physiological, and biochemical conditions that might indirectly influence behavioral development and acquisition.4