Chapter 41 Left Brain


It is impossible to consider brain development and the development of the individual without at least scanning some of the basic neuroscientific findings about what is called the asymmetry of the brain.  This asymmetry of the brain and its hemispheric specialization, or hemispheric laterality (although there is usually “bilateral participation of he hemispheres in the vast (tdm/177) array of mental processes (tdm/178)” is evident and active in the human fetus and develops further throughout an individual’s life.  Siegel states:


“…critical, analytic, intellectual, rational, and conscious modes of thought. (tdm/178)”

“… left hemisphere tends to have an “assertive” motivational state governing active engagement with the world of others…[and]… is more active in motor expression and “approach,” mediated by activity of the neurotransmitter dopamine.  (siegel/tdm/175)”

“…the ventral pathway (dominant on the left side) has a motivational bias toward specific details of objects and involves a feedback system whereby representations of present perceptions have a high degree of tight monitoring of the generation of behavioral output.  Such a feedback process lends itself to object perception and competence in analytic processing, which may “be especially involved in object memory and the fine-tuning of the neocortical representation of objects whether the objects are conceptual or perceptual. (quoting Tucker, et.al)  (siegel/tdm/176)”

“Note that the traditional verbal-nonverbal distinction between the left and right hemispheres is not completely accurate.  Examples of this include the contribution of the right hemisphere for understanding metaphor, paradox, and humor.  Also, the reading of stories activates both left- and right-hemisphere processes more readily than the reading of scientific texts, which primarily activates the left hemisphere.  (siegel/tdm/179)”

“On the left side of the brain are more slowly acting, linear, sequentially active, temporal (time-dependent) processes.  Verbal meanings of words, often called “digital” representations, are a primary mode of processing for the left side.  The left hemisphere is thought to utilize monosemantic “packets” of information as basic representations, which are then  processed in a slower, linear mode.  Examples of linear processing are reading the words in this sentence, aspects of conscious attention, and deterring the sequence of events in a story.  Our language-based communication is dominated by this linear mode of expression and reception of “bundled” bits of symbols, which carry restrictive definitions and relatively clearly demarcated chunks of information.  This is quite distinct from the analogic representations seen, for example, in an artist’s painting or in a photograph.  We can translate these analogic components of the world into digitalized forms within words, but the translation is never completeIn this way, some authors argue that the right hemisphere more fully “sees the world for what it is,” whereas the left hemisphere must reduce the world much more into mentally defined, often socially constructed chunks of information. Siegel/tdm/179)”

“…the left hemisphere is involved in actively asserting communications via the right hand [in infancy]; these are more outwardly oriented, approach/assertive motor activities.  One can propose a perhaps simplistic but useful generalization here that the left hemisphere is motivated for externally focused attention and action…. On the left are the semantic memory representations of objects in the world which can be manipulated and communicated to others as distinct packets of information. (siegel/tdm/180)”

has a “drive to explain” – interprets – “attempts to reason to explain cause-effect relationships in the limited pieces of information with which it is provided.”  tdm/180

“Under normal conditions, such sustained syllogistic reasoning allows us to try to explain how things function and why the world is he way it is.  In this manner, the left hemisphere is the center of the cognitive machinery that attempts to explain events and therefore…is the primary motive to narrative thinking.  (siegle/tdm/181)”

“More regulated, even-keel emotional states of mild interest and calm are thought to be the left hemisphere’s range of affective experience.  (siegel/tdm/183)”

“Left-sided overactivation…yields states of happiness and contentment.  (siegel/tdm/183)”  might call the left hemisphere optimistic

“…emotions eliciting approach behaviors are experienced on the left side…”  tdm/183

“Social emotions – adaptations of emotional states to meet the needs of social situations —  are thought to be functions of the left hemisphere…(tdm/183)”  .Display rules – the culturally transmitted lessons about which, and how, emotions an be expressed in social settings – determine the social appropriateness of affective expression and are presumably mediated by the left hemisphere.  This view is consistent with the notion proposed earlier that the left hemisphere has an inherent external bias toward attention and memory processing….The tightly controlled, routinized output of social display rules is a product of the left hemisphere in this model.  (siegle/tdm/184)”

“Of note is that the left hemisphere appears to be inept at reading nonverbal social or emotional cues from others…..the left hemisphere may have little innate ability to construct or be conscious of such a nonverbal, nonlogical view of the world.  However, the left hemisphere is able to mediate social display rules and can assess complex social situations to some degree.”  (siegel/tdm/185)”

“The left [hemisphere]…has fewer inputs from the body and is able to use the abstract manipulations of linguistic representations to allow us to experience a “higher-order consciousness”:  Linguistically, we are able to reflect on the past and the present, and to anticipate and plan for (siegel/tdm/196) the future [left brain task].  Such abilities also allow us to create new combinations of things, in our minds and in the world….the logical, linear, detail-focused, linguistic left brain is crucial for human creativity as well as technology.  It is essential for getting the message into shareable packets of socially transmissible information.  (siegel.tdm/197)”

“The left hemisphere…is able to categorize perceptions based on prior experience from a top-down view. (siegel/tdm/197)”

“The left hemisphere…is built for “vertical integration,” with intraregional linkages allowing for detailed assessment of a single mode of representation.  For example, when a perceptual representation matches a linguistic category, it allows the left hemisphere to move deeply into routinized responses in its top-down processing.  These linear relationships are well established and link specific inputs with particular outputs.  The left hemisphere is therefore said to be built for a categorical response to routine stimuli.  In other words, the left hemisphere’s experience of reality is literally created by the more rigidly established definitions of its linguistic packets of representations:  words. (siegel/tdm/198)”

“top-down categorizations with routinized perceptions and behaviors (siegel/tdm/198)”

“The monosemantic, linguistic left-hemisphere – filled with modes of information processing that rely upon the rules of logic and reason, and able to negotiate in an external world of symbols and language – can often find its active place in interacting with the outside world.  The left hemisphere’s experience of consciousness may be better equipped to deal with the world in abstract concepts independent of emotional context. (siegel/tdm/204)”

“The left hemisphere has been described as having a logical “interpreter” function that uses syllogistic reasoning to deduce cause-effect relationships from the representational data it has available to it. (siegel/tdm/205)”


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