The Nervous System :: Biology, Neurons, Axon

The peripheral nervous system consists of two separately functioning components: the sensory division and the motor division. The sensory division provides appropriate responses from sensory receptors to the central nervous system. Sensory neurons transmit reactive responses from the periphery to the central nervous system while the motor division conducts action potentials from effector organs such as muscles and glands. In contrast, motor neurons transmit action potentials from the central nervous system toward the periphery (Seeley et al., 2005). Neurons and their Electrical Activity The nervous system is composed of millions of nerve cells called neurons. Neurons are the parenchyma of the nervous system which performs every function of the nervous system from simple sensory functions to complex thinking and analysis. Neurons, upon receipt of stimuli, transmit responsive signals to other neurons or to effector organs. Clark (2005) observes that the anatomy of a neuron is composed of four main parts; the cell body, the dendrites, the axon, and the nerve fibers. Given the importance of each of the neuron components, it is important to discuss how each work separately and in tandem to achieve efficient and appropriate responses in the human body. Varying in diameter and containing a single nucleus, the cell body is the primary component of the neuron. The nucleus of the neuron provides information for protein synthesis and contains most of the organelles of the neuron. Seeley et al., (2005) write that the cell body contains large numbers of mitochondria because of its high metabolic function and also abundant rough endoplasmic reticulum’s which referred to as Nissl bodies. The dendrites of a neuron are cytoplasmic extensions that reach out from the cell body like arms and contain a full array of cellular organelles, such as mitochondria, chromatophilic substance, and ribosomes. The most important feature of a dendrite is its electrical activity. Dendrites receive information from other neurons and transmit them toward the cell body, then produce electrical impulses referred to as graded potentials. Graded potentials can have varying degrees of depolarization or hyperpolarization. These graded potentials arise in the dendrites or in the cell body as a result of various stimuli and are important in initiating action potentials in neurons. As the graded potential passes through a cell body, it may initiate an action potential at the base of another cytoplasmic projection which is the axon (Clark, 2005). An axon is a long cell process extending from the neuron cell body.

Does Culture Determine Your Theory of Mind Essay

What has distinguished Homo sapiens from non-human organisms is their ability to develop a theory of mind (Scholl & Leslie, 2001). Premack & Woodruff (1978) originally defined theory of mind as being the tendency to make attributions about behaviour based on acquired knowledge of mental states, such as belief, desire and intention. An equally important aspect of theory of mind concerned the individual’s ability to understand the subjectivity of mental states, comprehending that other individuals have desires and beliefs that differ significantly from one’s own, an understanding that is highly important to human functioning (Baren-Cohen, 1995). This essay questions the influence that culture has on the development of a theory of mind. What was of primary interest in this essay was to investigate the extent to which theory of mind was characterized by universal processes of development and whether underlying cultural factors were responsible for the timing and development of theory of mind. Certain marked cultural differences were suggested as influential variables which could determine the development of a theory of mind, these being parenting styles, number of siblings and executive function which were thought to play a pivotal role in the development of a cultural identity (Lillard, 1998). In the context of cross-cultural comparison, a critical assessment of the false-belief task was conducted. The validity and reliability of the false-belief task was analyzed in relation to the development of theory of mind, and alternative explanations and measurement tools were provided which would allow for a more sensitive and reliable cross-cultural comparison to be made. Described as onto-genetically universal, theory of mind is a construct of human psychology and biology that is universally applicable to every culture (Liu, Wellman, Tardif & Sabbagh, 2008) . A unanimous result from twenty five years of research has reported that a theory of mind is developed in early childhood and exhibited from the age of five or six years old as result of progressive stages of development (Lillard, 1998). Many researchers (e. g Liu et al. , 2008; Wellman, Cross & Watson, 2001) have observed parallel developmental trajectories between western and non-western cultures in relation to the age at which a child acquires a theory of mind. Callghan, Rochat, Lillard, Claux, Odden & Itakura (2005) observed the cross-cultural development of theory of mind in samples of 12-31 children and declared there to be a ‘critical period’ of development between the ages of three and five years old when children begun to conceptualize and understand the difference between belief and reality. From a remote bush community in western Africa, to a mountain village in Peru, researchers (e. g. Avis & Harris, 1991) have observed the universal development of a theory of mind. The communicative purposes of theory of mind are invaluable to the survival and higher functioning of human kind. Cross-culturally, theory of mind is relevant in order to teach, deceive, inform and share planned actions (Baren-Cohen,1999). However, although this cognitive development is fundamental and pivotal to human functioning, research in this field of investigation has challenged the universality and applicability of theory of mind postulating that cross-cultural variations were responsible for determining and influencing the timing and stages at which theory of mind developed. Many prominent research studies have been published in the literature, arguing for the influence of culture on the development of a theory of mind (Wellman et al. , 2001). Astington (2001) has argued that although cross-cultural variation does not reflect a child’s ability to acquire a theory of mind, there may perhaps be sociocultural variances in early childhood experience that could potentially influence how and when a child achieves theory of mind. Similarly, studies have observed a discrepancy in the timing of development across certain industrialized cultures, an example being Canada and the United Kingdom (Wellman et al. 2001), and Japan and North Korea (Oh & Lewis, 2008). A meta-analysis of cross-cultural performance on false-belief tasks was conducted by Liu et al. , (2008) which investigated whether culture contributed to the development of theory of mind. A meta-analysis was conducted on 200 conditions (16-24 children per condition) of children from mainland china and Hong-Kong in order to assess whether the difference in cultural beliefs and values between these two culturally diverse samples had a significant impact on the timing of development. Increasingly more westernized and individualistic, Hong-Kong was predicted to mirror the North American trajectory of development in that children would be more likely to perform above chance on the false-belief task. Liu et al. , (2008) observed that Chinese children were more likely to under-perform on false-belief tasks in relation to their Japanese counterparts and that this resulted in a difference of up to 2 years in timing of false-belief acquisition. However, like many comparison studies, the results of this study were potentially confounded due to relatively small sample size. A condition of 16-24 participants did not allow for methodological error or research bias. Contradictory evidence and potential methodological errors in relation to cross-cultural comparisons has resulted in a thorough examination of the measurement tools used to study theory of mind. A seemingly reliable and valid measurement tool, the false-belief task has to some extent dominated the theory of mind model over the course of twenty five years (Dennet, 1978 as cited by Wellman et al. 2001). Astington (2001) reported that there exists â€Å"a danger in letting a single task become a marker for complex development†, as reliance on a single measurement construct can record potentially confounding results, leading to improbable and invalid conclusions. The ‘chocolate and cupboard’ false-belief task was developed by Wimmer & Perner, (1983) in order to assess whether a child had the ability to understand that their mental representations of the world differed from reali ty. Many researchers have found methodological flaws in the false-belief task claiming that it is unnecessarily difficult (Sullivan & Winner, 1993). A cross-cultural study conducted by Wellman et al. , (2001) confirmed that many children failed the false-belief task due to confusion and lack of understanding. A secondary criticism of the false-belief task has been made in relation to the limitations it places on performance in that it does not take into account fundamental components of theory of mind (De Rosnay, Pons, Harris & Morrell, 2004). Therefore, in order for a valid cross-cultural comparison to be made it was necessary to examine other important mental states such as emotion, desire and intention (De Rosnay et al. , 2004). A five step Theory of Mind scale was developed by Wellman & Liu (2004) in order to conduct a cross-cultural comparison of theory of mind. Preschoolers in North America (Wellman & Liu, 2004) , Australia (Peterson & Wellman, 2009) and Germany (Kristen, Thoermar et al. 2006) were found to follow the same ordered sequencing of conceptual developments, these being diverse desires, diverse beliefs, knowledge access, false beliefs, hidden emotions (Shahaeian, Peterson, Slaughter & Wellman, 2011). Although an identical trajectory of development was reported in many western cultures, a study conducted by Wellman et al. , (2004) discovered an interesting cross-cultural difference in relation to Chinese preschoolers who, although following the same steps of development, completed them in a different order with knowledge access being learned before diverse beliefs. Although there does not appear to be a cross-cultural difference in the mastery of theory of mind, the emphasis placed on knowledge access in Chinese preschoolers over diverse beliefs in western preschoolers is consistent with the importance that collectivist societies associate with social harmony over self-expression and individual beliefs. Reliance on one particular measurement tool has resulted in many extravagant and inconclusive claims being made, one such example being that researchers have associated a below chance performance on a false-belief task with an underdeveloped theory of mind (Astington, 2001). However, many researchers have argued that a three year old’s failure on the false-belief task could be indicative of linguistic underdevelopment or confusion rather than an absence of theory of mind. Leslie (2000) conducted qualitative reviews of cross-cultural performance on false-belief tasks in order to assess whether certain aspects of the methodology were inconsistent across cross-cultural testing. Methodology was found to differ in relation to the type of question asked, nature of the protagonist and type of task. Similarly, there was an inconsistency in the phrasing of the questions across many of the studies, with certain children being asked a question in terms of belief (Where does John think his chocolate is? ) or in terms of speech (where does John say his chocolate is? ). Efforts to reduce methodological error and improve performance have been made by many researchers (e. g. Chandler, Fritz & Hala (1989) in order to demonstrate the plasticity and flexibility of theory of mind. Chandler et al. (1989) found that if the experimental design of the false-belief task was manipulated by implying deception and trickery, performance was more likely to increase. A cross cultural comparison reported similar results when young children actively participated in deception. However, although these results may have provisionally provided an explanation for improved performance, it must be noted that above chance performance on this task did not confirm a child’s ability to conceptualize but mere ly emphasized their ability to ‘play along’ . Due to flaws in methodology and reliance on the false-belief task, researchers have failed to provide consistent and valid results in relation to a cross-cultural comparison of theory of mind. In light of these contradictory results and inconclusive explanations, alternative variables have been analyzed in order to expand on the literature pertaining to cross-cultural differences in theory of mind. Vinden (2001) was of the opinion that the development of a theory of mind aptly reflected parental influence in relation to cultural and moral expectations. Children emulated and modified their behaviour according to their parents’ example, therefore for a child to be capable of predicting and understanding another individuals’ mental state positively reflected parent-child intervention in the early years of their childhood. A cross-cultural comparison of theory of mind assessed whether parental attitudes of Korean-American and Anglo-American mothers influenced how their children developed mental states such as desires, beliefs and intentions (Vinden, 2001). Two previous studies conducted by Kim, Kim & Rue (1997) and Farver, Kim & Lee (1995) reported certain cultural differences between Korean-American and Anglo-American individuals. Korean-Americans were reported as valuing interdependency, social harmony and self-control in favour of individual orientation, symbolic play and independence, traits which were synonymous with the individualistic Anglo-american society. Importantly Korean-American parents were seen as obeying an authoritarian structure of parenting in contrast with Anglo-American parents who favoured an authoritative model . In light of the results obtained by the Kim et al. , (1997) study, it was hypothesized by Vinden (2001) that children of authoritative mothers would be more likely to outperform children of authoritarian mothers on the theory of mind tasks. The results reported were surprising, in that five year old children of authoritarian Korean-American mothers outperformed their Anglo-American age mates on theory of mind tasks, however children of authoritarian Anglo-American mothers were found to under-perform on theory of mind tasks. What could be concluded from this study was that performance on theory of mind tasks could in fact be influenced by parenting styles, but what constituted acceptable parenting was subjective to cultural introspection. In other words, a similar endpoint of development was reached across cultures, due to parenting styles that obeyed a cultural value system (Vinden, 2001). Similarly, a cross-cultural comparison of theory of mind has been made in relation to the number of siblings a child may have. A study conducted by Ruffman, Perner, Naito, Parkin & Clements, (1998) reported a remarkable finding that suggested how a child’s theory of mind could be predicted based on the number of older siblings they possessed. According to Brown, Donelan-McCall & Dunn (1996), children with older siblings developed mental representations about the world around them through symbolic play. Many researchers have argued for the importance of symbolic play in establishing a theory of mind (Leslie, 1987) due to the fact that through discussion and pretend play younger children were exposed to false-belief situations enabling them to emulate the behaviour exhibited by older siblings. However, it is important to remain critical when discussing the importance of symbolic play due to the fact that although above-chance performance on theory of mind tasks may be recorded, the extent to which conceptualization and false-belief is properly understood demands further explanation. Reiterating what has been previously stated by Vinden (2001), it was important to acknowledge that, although the same end point of development was reached across cultures, the stages of development differed based on cultural intervention. In recent years, the skills associated with executive function have been proposed to contribute to the development of theory of mind (Moses, 2001). Many researchers interested in cross-cultural comparison have conducted studies in order to ascertain whether the development of executive skills is directly influenced by cultural beliefs and values. Interest in this area of research has come about due to the importance of understanding theory of mind in conjunction with the development of cognitive processes (Moses, 2001). Executive function is an umbrella term used to describe a plethora of cognitive processes such as inhibition, verbal reasoning, problem solving and working memory which contribute to the development of theory of mind. Executive function has been assessed across a diverse range of cultures in order to determine whether development of executive function skills differ across cultures, and whether this difference in development affects the acquisition of a theory of mind.

Can We Think Without Language.. - 1188 Words

CAN WE THINK WITHOUT LANGUAGE Many anthropologists, linguists, psychologists, biologists and other academics have attempted to tackle this question in recent decades. It is sort of chicken or egg conundrum: Did human beings first develop the physical capabilities for language (larger brains, vocal tract, etc) with the actual development of language following it, or had the capabilities for speech already arisen and only with the development of physical production of language itself follow? Obviously, it is difficult for us to think about things without using language in our minds while we reason. Yet if you ve ever had a smart pet and watched them perform a task, you know that they operate on a largely trial-and-error basis.†¦show more content†¦The Hopi language has a single word for all flying objects other than birds. The hypothesis states that hopi speakers think differently about flying objects than do speakers of languages that do not categorize the world in the way. The Hanunoo people of the Phillipine Islands are said to have names for 92 species of rice but all 92 varieties of rice are, for the English speaker, simply rice. A more recent study, however, comparing English children and Himba children from Africa suggests that colour categorises in a given language have a greater influence on colour perception. The English language contains 11 basic colour terms whereas the Himba language has only 5. Himba children made fewer distinctions among coloured titles than did English children. For example, Himba children categorised under the colour term â€Å"zoozu† a variety of dark colours such as dark shades of blue, green, purple red, and the colour black. English children distinguished among these colours and remembered the different hues better when retested on which ones they had seen earlier. Language not only influences how we think but also may influence how well we think in certain domains. 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