The Biological Basis for Human Thought and Behavior

Abstract

This paper addresses the biological basis for human thought and behavior, within the context of the historical basis of biopsychology, the structure of the brain, the mechanisms of neural activity, and the link between biopsychology and other fields of psychology. 

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Biological Psychology Paper

The structure of the brain and the function of the brain are two entirely distinctive, but complementary means by which to understand the physical happenings of human thought. The basic underlying assumption of biopsychology is that human thought can be boiled down to nothing more or less than a complex network of neurochemical reactions in the material world (Wickens, 2005). This is an assumption that James Mill would embrace wholeheartedly, but his son, John Stuart Mill would argue that “…the whole is greater than the sum of its parts” (Goodwin, 2005, p. 47). However, regardless of whether the sum of the parts is equal to the whole or not, the inner workings of the parts are still the subject of this paper. Incumbent on the understanding of the physicality of human thought is the historical development of biological psychology, an examination of the core mechanisms of neural activity and the structure of the brain, and a thorough look at the link between behavioral genetics and biopsychology.        

There are two main methods by which to approach matters of history: personalistic history, the “Great Man” theory; and naturalistic history, which is wholly concerned with how historical mechanisms act on individuals (Goodwin, 2005). The history of the development of biopsychology is littered with great people and great discoveries, so the personalistic approach would seem fitting. As with many great western discoveries, Plato (429 – 348 BC) was a progenitor of the belief that the brain was the basis of reason; however, as with most of Plato’s insights he was ahead of his time, understanding the what without the how. From there, Galen (AD 130 – 200) proposed that animal spirit in the ventricles of the brain, fueled by the vital spirit from the heart and air through the nostrils, explained human behavior and voluntary movement. Nemesius took the next step and hypothesized localized brain function between the various ventricles claiming that “…the lateral ventricles were the site of sensory and mental impression, the third ventricle was the site of reason and the fourth ventricle was the site of memory” (Wickens, 2005, p. 5). Furthermore, Descartes (1596 – 1650) mixed the aforementioned theories and suggested that the animal spirits in the brain were acted upon by the pineal gland, at the bequest of the soul, as a link between the cerebrospinal fluid of the third ventricle (i.e. animal spirits, the soul) and the brain. It was not until Galvani that the electrical nature of the neural activity was put into a cohesive, experimentally reproducible system. However, Galvani still held to the animal spirits of Galen and Descartes as the underlying mechanism of neural activity, albeit with an electrical twist. Nonetheless, it was not until after the discovery of the cell that Golgi (1843 – 1926) was able to stain and microscopically examine a nerve cell for the first time. Then Cajal (1852 – 1934), using Golgi’s staining procedure, subsequently mapped nearly every type of cell in the human brain. It was left to Otto Loewi (1873 – 1961) in 1921 to discover that nerve cells communicated by chemical transmission. Finally, in 1952 Hodgkin and Huxley, building on the discoveries of John Young, published their work summarizing the neural action and chemical composition of a giant squid neuron, thereby finally elucidating the actual means by which neurons produce electrical impulses. Now, with the history of biopsychology firmly in hand, the other hand is free to grasp the actual mechanics of neural activity and brain structure.

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It would seem prudent to progress from the macro to the micro, so first brain structure and then the building blocks of human thought, neurons. The nervous system is broken up into two main sections: the central nervous system and the peripheral nervous system. The purpose of the peripheral nervous system is to relay sensory and motor impulses from/to the rest of the body back to/from the central nervous system. The central nervous system is separated into two segments: the brain and the spinal cord. The spinal cord is the link between the peripheral nervous system and the brain but does have some capability to receive, interpret, and manipulate sensory and motor impulses. The brain itself is broken up into three main divisions: the brain stem, which handles involuntary responses (breathing, heart rate, posture), the midbrain, which is concerned with visual and auditory functioning as well as the regulation of cerebral stimulation, and the forebrain, which houses the link between the brain and the endocrine system (hypothalamus) and the place of learning, memory, and language (cerebral cortex). The brain accomplishes all of these extraordinary feats of cognitive ingenuity through the mechanism of the neuron. The neuron’s basic structure is comprised of a cell body, the axon hillock, the axon, and the axon terminals. The cell body encompasses the nucleus of the cell as well as the place of normal cell metabolism and the dendrites, which receive signals from other neurons. The axon hillock is the place where the cell body meets the axon and is pivotal in the conduction of electrical impulses (action potentials). The axon is the long, slender projection of a neuron that acts to conduct electrical impulses away from the cell body to the axonal terminals. The axonal terminals then release neurotransmitters into the synapses, the gap between the neurons, which in turn excite the next neuron. It is in this manner that electrical impulses or action potentials are conducted from one neuron to the next, and it is through this process that human thought takes place on a physical level. Now, with both hands full it is time to metaphorically sink the teeth of exploration into the relationship between biological psychology and other branches of psychology.

The nature vs. nurture debate…controversy…dichotomy has been the subject of much discussion in the field of psychology for some time now. It is only recently that we have begun to understand that nature, the genetic and biological foundation of human behavior, and nurture, the environmental building blocks of human behavior, are complementary rather than opposing. For example, which plays more of the music…the violin or the violinist? This question is null from the onset because without the violin there would be no music, without the violinist there would be no music (Kowalski & Westen, 2005). In the same way, nature and nurture form a unified web of interaction which brings about human behavior. A prime example of this relationship is scientific research which shows that heritability of traits is lower during infancy and higher during middle childhood, which would imply that nurture acts to reinforce nature, rather than contradict nature (Plomin & Spinath, 2004). There is also evidence to suggest that nurture also encourages diversity between siblings, underscoring the long-held belief that, “…nature prevails enormously over nurture” (Plomin & Spinath, 2004; Plomin & Crabbe, 2000). In all, the genetic basis of human behavior between monozygotic twins, adopted out at birth (or closely thereafter) is only a correlation of .50, which leaves plenty of room for nurture. As behavioral genetics searches the human genome for a genetic basis for human behavior, biological psychology at the same time seeks a purely physical explanation for human behavior, wrapped up in the understanding of the neuronal activity. 

In conclusion, with both hands full, one with the historical context of biological psychology and the other with the underlying mechanisms of neural activity and the structure of the brain, and the teeth of exploration satiated by an ample comprehension of the nature vs. nurture debate; it should be clear that the structure of the brain and the function of the brain are two entirely distinctive, but complementary, means by which to understand the physical happenings of human thought  

References

Goodwin, C. J. (2005). A history of modern psychology (2nd ed.). Hoboken, NJ: Wiley.

Kowalski, R., & Westen, D. (2005). Psychology (4th ed.). Hoboken, NJ: Wiley.

Plomin, R., & Crabbe, J. (2000). DNA. Psychological Bulletin, Psychology in the 21st Century, 126(6), 806-828. Retrieved March 24, 2009, from EBSCOHost Database. 

Plomin, R., & Spinath, F. M. (2004). Intelligence: Genetics, Genes, and Genomics. Journal of Personality and Social Psychology, 86(1), 112-129. Retrieved March 24, 2009, from EBSCOHost Database. 

Wickens, A. (2005). Foundations of biopsychology, 2e. Upper Saddle River, N.J.: Pearson Hall. 

Paper Topic

Prepare a 700 to 1,050-word paper in which you analyze biological psychology. Be sure to address the following items in your analysis:

  • Define biological psychology and examine its historical development.
    • Identify the important theorists associated with associated with biological psychology.
    • Describe the relationship between biological psychology and other fields in psychology and neuroscience.
    • Describe the major underlying assumptions of a biopsychological approach.

Include at least three references.

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