VI
Mark học AIFrom the split-brain lab of the 1960s to the online quiz "which brain are you?"
Sources: Nielsen et al., PLOS ONE 2013; Knecht et al., Brain 2000; Gazzaniga, Bogen and Sperry, PNAS 1962; Arsalidou and Taylor, NeuroImage 2011; Dietrich and Kanso, Psychological Bulletin 2010.
How did a Nobel-winning finding about surgically divided brains turn into a way of sorting ordinary people, and where does it go wrong? The short answer: the hemispheres divide the work, but people do not divide into two kinds.
Each retelling dropped one important condition.
Sources: Gazzaniga, Bogen and Sperry, PNAS 1962; Sperry, Nobel lecture 8 Dec 1981, printed in Science 217 (1982), p. 1226; Dekker et al., Frontiers in Psychology 2012, table 1; Nielsen et al., PLOS ONE 2013. The description of Ornstein's book as part of the "left/right fad" is a secondary source.
10 common claims about left and right brains, checked against the original research. Click each row to see why.
From Broca in the 1860s to modern measurements. Among healthy strong right-handers, only about 4% have language mainly on the right (Knecht et al., Brain 2000).
The research line began with Gazzaniga, Bogen and Sperry (PNAS 1962) and earned Sperry the 1981 Nobel. These are results in surgical patients, not in ordinary people.
In a survey of 242 teachers interested in brain science, 91% in the UK and 86% in the Netherlands agreed with the "hemispheric dominance" statement; only 3% and 4% answered correctly (Dekker et al., Frontiers in Psychology 2012, table 1).
The meta-analysis by Mihov et al. (2010) found a relative right advantage. The review by Dietrich and Kanso (2010) concluded creativity is not tied to one region or one hemisphere. Corballis (2014): creative thought activates a widespread network. "A slight edge on some tasks" is far from "creativity lives in the right brain".
They do lean right in many people (Anderson, University of Utah press release 2013: attention more on the right). But "leaning" is not "owning": the left side still takes part.
That is the classic reading. Pinto et al. (Brain 2017) tested 2 patients who could respond to stimuli on either side and proposed "split perception, undivided consciousness". Volz and Gazzaniga (2017) disagreed. The question is open.
Nielsen et al. (2013) analysed 1,011 people: lateralised connections did not go together within individuals, and there was no whole-brain "left-brained" or "right-brained" type.
Calculation relies on fronto-parietal networks on both sides (Arsalidou and Taylor, NeuroImage 2011); number sense uses parietal regions in both hemispheres (Dehaene et al., 2003). The verbal side of a maths problem leans left, like anything involving language.
Even among strong left-handers, only about 27% have language mainly on the right; about 3/4 still have it on the left (Knecht et al., 2000). Handedness says nothing about a "brain type".
If no such types exist in the brain (Nielsen 2013), the quiz only measures self-reported preferences and gives them a scientific-sounding name. "Hemisphere balancing" exercise programmes are also listed by Dekker et al. among educational neuromyths.
Sources: as noted in each row; full list in Part 8.
Scores are Mark's assessment based on the sources in Part 8, not figures from a study.
A half-truth about the brain turned into a falsehood about people.
In his 1981 Nobel lecture, Sperry wrote about the growing wave of "semipopular extrapolations and speculations" on left-brain and right-brain functions, and cautioned: "The left-right dichotomy in cognitive mode is an idea with which it is very easy to run wild."
The myth survives because it is handy: two boxes, one quiz, one label. It also sounds scientific, because there really is a Nobel Prize behind it. Corballis (2014) calls most of these speculations "exaggerated or ill-founded".
Sources: Sperry, "Some Effects of Disconnecting the Cerebral Hemispheres", Nobel lecture 8 Dec 1981, Science 217 (1982), p. 1226; Corballis, PLOS Biology 12(1), 2014.
Applies when you hand out work, form a project team, write a year-end review, or hear someone say "she's just not the creative type".
Original papers first. The full text of some papers could not be downloaded; details were checked against abstracts and results tables on the original pages. Secondary sources are flagged.