Shared Manifold Hypothesis



SHELDON'S TYPE THEORY. = somato-type theory = typology theory. The American psychologist/physician William Herbert Sheldon (1899-1977) formulated a constitutional theory of personality that emphasizes the importance of the physical structure of the body and biological-hereditary factors ("constitutional" variables) as major determinants of behavior. The term constitution refers to those aspects of the person that are relatively fixed and unchanging (such as morphology, physiology, genes, endocrine functioning) and is contrasted with those aspects that are relatively more labile and susceptible to modification by environmental pressures (such as education, habits, and attitudes). The constitutional psychologist looks to the biological substratum of the person for factors that are important to the explanation of human behavior. Constitutional psychology assumes the role of a facilitator or bridge connecting the biological with the behavioral domains. In Sheldon's approach, a hypothetical biological structure (morphogenotype) underlies the external, observable physique (phenotype) that determines physical development and molds behavior. In order to measure physique, Sheldon devised a photographic technique using pictures of the individual's front, side, and rear in standard poses. This procedure is called the somatotype performance test. After examining and judging about 4,000 of these photographs, Sheldon and his associates concluded that there are three primary dimensions or components concerning the measurement and assessment of the physical structure of the human body: endomorphy - a body that appears to be soft and spherical; mesomorphy - a body that appears to be hard, rectangular, and muscular; and ectomorphy - a body that appears to be linear, thin, and fragile. All participants in Sheldon's photographs could be assigned a score of from one to seven for each of the three components and, with further an-thropometric measurements, a complete description of the somatotyping process of individuals was possible. According to Sheldon, the idea of somatotype is an abstraction from the complexity of any specific physique, and he developed various secondary components by way of accounting for the great variation across individuals. Secondary components include: dysplasia - an inconsistent or uneven mixture of the three primary components in different parts of the body; gynandromorphy -called the "g index" and refers to the degree that one's physique possesses characteristics ordinarily associated with the opposite sex; and textural aspect - a highly subjective physical aspect reflecting "aesthetic pleasing-ness." Sheldon also developed three primary components of temperament along with their associative traits: viscerotonia (this is paired with endomorphy) - is characterized by enjoyment of food, people, and affection; soma-totonia (this is paired with mesomorphy) -refers to love of physical adventure and risk-taking; and cerebrotonia (this is paired with ectomorphy) - is characterized by a desire for isolation, solitude, and concealment. The three temperament dimensions, in conjunction with a list of 20 defining traits for each dimension, constitutes Sheldon's scale for temperament. Sheldon's research led to the strong confirmation of the constitutional psychologist's expectation that there is a noteworthy continuity between the structural/physical aspects of the person and his/her functional/behavioral qualities. Although Sheldon was successful in isolating and measuring dimensions for describing physique and temperament, he cautioned that the dimensions should not be examined in isolation one by one but, rather, the pattern of relations between the variables should be studied. Perhaps the most frequent criticism of Sheldon's constitutional theory is that it is no theory at all but simply consists of one general assumption: the continuity between structure and behavior, and a set of descriptive concepts for scaling physique and behavior. Other criticisms focus on procedural/methodological flaws in Sheldon's research, and on the fact that his notion of somatotype is not invariant in the presence of nutrition, age, cosmetic surgery, and other environmental changes. See also GALEN'S DOCTRINE OF THE FOUR TEMPERAMENTS; KRETSCHMER'S THEORY OF PERSONALITY; PERSONALITY THEORIES; TRAIT THEORIES OF PERSONALITY. REFERENCES

Sheldon, W. H. (1940). The varieties of human physique: An introduction to constitutional psychology. New York: Harper. Sheldon, W. H. (1942). The varieties of temperament: A psychology of constitutional differences. New York: Harper.

Sheldon, W. H. (1949). Varieties of delinquent youth: An introduction to constitutional psychiatry. New York: Harper.

Sheldon, W. H. (1954). Atlas of men: A guide for somatotyping the adult male at all ages. New York: Harper. Humphreys, L. (1957). Characteristics of type concepts with special reference to Sheldon's typology. Psychological Bulletin, 54, 218-228. Sheldon, W. H. (1971). The New York study of physical constitution and psychotic pattern. Journal of the History of the Behavioral Sciences, 7, 115-126.





SHORT-TERM AND LONG-TERM MEMORY, THEORIES OF. The dualmemory theory holds that memory, generally, is a two-stage process: short-term memory (STM) that allows for the retention of certain information for very brief periods of time, and long-term memory (LTM) that permits information retention for longer periods of time (cf., the storage-and-transfer model of memory - is a "multistore" model of memory that states that there are three types of memory: sensory, short-term, and long-term). STM or "immediate memory" is a hypothesized memory system having a limited amount of information capacity, and capable of holding the information for a maximum of 20-30 seconds [cf., primary memory hypothesis - in 1890, the American psychologist/philosopher William James (1842-1910) suggested that a "primary" memory system is closely related to consciousness and differs from memory for general knowledge; later, in 1969, this memory system came to be known as "short-term" or "working" memory; iconic memory/store -refers to a theoretical sensory register, or "sensory information store," allowing a visual image to persist for about half a second to two seconds after its stimulus has terminated; this type of memory/image/storage was studied initially by the Hungarian physicist Johann Andreas von Segner (1704-1777) in the mid-1700s, and most currently by the American psychologists George Sperling (1933?- ) and Ulrich Neisser (1928- ); cf., also, echoic memory/store theory - one of the hypothesized "sensory registers" allowing an auditory image to persist for up to two seconds after its stimulus has terminated, making speech intelligible and allowing one to localize sounds via binaural time differences between the arrival of sound at the two ears; precategorical acoustic memory/store theory - an echoic memory/store that is posited as holding auditory information for brief durations before it has been modified by information processing; for instance, in serial digit recall tasks, the final two items in a list of digits are recalled better when the list is heard than when it is read, but the effect is lessened if the auditory list is followed by a verbal suffix that does not need to be recalled; such an auditory suffix effect indicates the existence of an "auditory memory trace" that decays rapidly and may be suppressed by other verbal information; post-categorical acoustic memory/store theory - is a hypothesized memory store for verbal information that has been modified by a degree of information processing, in particular, syntactical analysis/processing; distributed memory storage/theory - holds that mental activity is due to the integrated activity and functioning of several brain components, where memory is distributed widely, and only different aspects of memory are stored in different locations in the brain; and is compared with localized memory storage/theory, which asserts that specialized memory structures in the brain

- such as "Broca's area" for speech production

- are involved in particular mental activities; cf., limited-capacity retrieval hypothesis -posits that STM is of finite capacity and can store only a few facts at one time, and its limited capacity appears to restrict the number of feelings, ideas, and cognitions that can be considered, or carried out, at any given time; Miller, 1956; recitation theory - holds that memory may be optimized when material is rehearsed; reality monitoring hypothesis - is the hypothesized process/act of discriminating between genuine memories that are gained through perception from external reality and the apparent memories that are achieved internally via imagination; such discriminations tend to break down in the course of many mental disorders such as schizophrenia and delusional disorder; the hypothesis refers, also, to the idea that most people are constantly observing themselves, their social and physical environments, and their alertness to making decisions about goals; adjacency effect - refers to a memory paradigm where a number of disconnected words/syllables that exceeds one's memory span are presented one at a time at short intervals (e.g., every two seconds), in a different random order on each of two or more trials; after each presentation, participants are asked to recall as many of the words/syllables as possible; the probability of recalling any given word is related to that word's "adjacency," that is, whether it follows, precedes, or is in-between words recalled on the previous trial; alternation-of response theory - suggests that proper division/parsing of a stream of stimuli is an important control device in STM tasks (e.g., lengthening the time interval between right-left alternation-task pairings reduces the error rate); and the Brown-Peterson paradigm/technique (Brown, 1958; Peterson & Peterson, 1959) - in memory research, refers to a procedure in which participants are asked initially to memorize some material, then they are distracted in some manner (e.g., "count backwards from some number by threes"), and fin-ally are asked to recall the originally memorized items]. One psychologist, the American cognitive scientist George A. Miller (1920- ), sets the STM capacity of humans to be about seven pieces, bits, chunks, or items of information in any given instance; and another theorist, the American cognitive scientist Herbert A. Simon (1916-2001), estimates the capacity of STM to be about five chunks of information. The chief utility of STM is connected with language/sentence comprehension: in order to understand a simple sentence one must be able to remember its beginning at least up to the time of its end. Theoretically, STM may be said to occupy a place on a temporal continuum between the two phenomena/ concepts of "sensory/iconic memory" and "long-term memory." That is, "sensory memory" (a "sensory register" that involves an "iconic store" for vision and an "echoic store" for audition) is a very short-time store of information that is activated when information is being processed by one's sensory organs ("sensory store") and has a duration of a few seconds; on the other hand, LTM is a long-term memory store of information that has a temporal capacity of periods ranging from about 30 seconds upwards to many years, even decades [cf., logogen theory - is a model for word recognition, formulated by the English cognitive psychologist John Morton (1933- ), and refers to a representation of a word or verbal unit in LTM, activated by speech sounds, writing, or an object/event to which it refers; imagen theory - refers to a representation of a visual image in LTM; and modality effect - refers to any result of the presentation of information through different sensory modalities; for example, the poorer immediate recall of simple verbal information presented to the visual modality as compared to the auditory modality, or the poorer long-term recall of complex verbal information presented to the auditory modality as compared to the visual modality]. LTM, or secondary memory, includes several categories of memory, such as: episodic memory (personal experience information is stored with mental tags about when, where, and how the information was acquired); semantic memory (factual information about the world, and the "meanings" of things, words, objects, etc.); perceptual memory (memory for visual, auditory, and other perceptual information, such as memory for people's faces and voices); declarative memory (conscious memory that may be communicated to others); procedural memory (memory for procedures, or complex activities, occurring without conscious awareness or thought of the process); and working memory (the hypothesized system that holds the input while one formulates an interpretation of it). An alternative to the conventional model of three separate memory stores (sensory, STM, and LTM) is the levels of processing theory formulated, primarily, by the Canadian-based Scottish psychologist Fergus I. M. Craik (1935- ), the Canadian-based Australian psychologist Robert S. Lockhart (1939- ), and the Estonian-born Canadian psychologist Endel Tulving (1927- ). The notion of levels of processing refers to the depth with which incoming information is analyzed and encoded, and ranges from superficial processing of sensory features to semantic and conceptual processing where deeper levels of processing result in longer-lasting memories (cf., screen/cover memory - in psychoanalysis, refers to a non-threatening memory of a childhood experience that is salient for its sharpness relative to the insignificance of its content, and indicates an unconscious memory of something that is important and/or threatening to the individual; and blocking memory - a memory that intrudes into consciousness and obstructs the retrieval of a different, though related, memory). According to levels of processing theory, in the processing and sequencing of information, the early sensory analyses are relatively automatic and effortless, whereas the later deeper analyses require more attention and effort. In support of this theory, research on memory for words/verbal materials indicates that recall is poor for words that are processed according to their visual appearance, a little better for words processed according to their sound, and best of words processed according to their meaning. Related to this theoretical approach is the domains of processing theory, which proposes that the more elaboration that is involved in the information processing of material at a given level of processing, the better the material will be remembered (cf., mnemon - a theoretical basic unit of memory referring to the minimum physical change in the nervous system that encodes a memory; and engram theory, or "memory trace" or "neurogram," is a hypothesized physical representation of a memory in the brain). See also FORGETTING/MEMORY, THEORIES OF; INFORMATION/INFORMATION-PROCESSING THEORY; WORKING MEMORY, THEORY OF.

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