Hi everybody! Long time no write! I’m sorry I haven’t written here for more than a year but here I am. I would like to thank all of you for reading my blog site. This isn’t a professional blog site, just my own research about neurodiversity and the conditions included, like learning disabilities and developmental disorders and also some insights and updates related to this. I’m also grateful regarding to all the comments you shared, it helped me a lot also in learning.

I may not be able to write more blog posts for now, but it is a big appreciation for reading all my articles and share your comments here.

Thank you very much for coming here. Please enjoy reading. ^_^

Theory of Mind and Mind Blindness

We humans are said to have intuition that we can easily decode feelings of another person. It isn’t in the sense that we guess what’s inside of a person’s head but rather we can understand what the other person is thinking through observation of body language, gesture, eye contact and tone of voice as well as language use. These are what we call “reading between the lines” or in other words non-verbal communication (or cues). We, especially most women can easily, decode non-verbal cues while most straight men can decode but not as intuitively  as women do (hence men can’t read women’s minds especially if she’s not in the mood??). When a person has good grasp of looking into human’s minds by just observing non-verbal cues, he or she is said to have good people skills and high empathy. And that’s what needed in order to have a good social life and to carry on with life itself.

This process is called the Theory of Mind.

Image courtesy of Slidshare. Are women really better than men in theory of mind?

But what about mind blindness? Does that mean that the mind can go blind?

A person is said to have mind blindness if he or she fails to understand the mental states of another person especially if he or she cannot interpret non-verbal cues. Just like in the drawing above.

To explain these further let’s truly define theory of mind and mind blindness.

What is theory of mind?

Theory of mind (ToM) is the ability to attribute mental states—beliefs, intents, desires, pretending, knowledge, etc.—to oneself and others and to understand that others have beliefs, desires, intentions, and perspectives that are different from one’s own.[1][2] This means that you as a person can “read” what another person thinks or feels through observation of non-verbal communication like body language and figures of speech. A person who has theory of mind can often develop empathy thus become good at people skills.

Most people (neurotypical) have theory of mind since early chidhood, hence can develop good social skills at a young age. However, people who have autism, Asperger’s syndrome, ADHD, non-verbal disorder and schizophrenia lack theory of mind, meaning they can’t read other people, making socialization difficult for them – a hallmark sign of these disorders.

How is theory of mind developed?

Theory of mind isn’t something that develops overnight. It usually begins in infancy or early childhood where they learn the early skills that they’ll need to develop their theory of mind later on. These skills include the ability to[3][4][5]:

▪ pay attention to people and copy them
▪ recognize others’ emotions and use words to express them (“happy”, “sad”, “mad”)
▪ know that they are different from other people and have different likes/dislikes from others
▪ know that people act according to the things they want
understand the causes and consequences of emotions (If I throw my toy, Mom will be mad)
▪ pretend to be someone else (like a doctor or a cashier) when they play

When they reach the ages 4-5 they really start to think about others’ thoughts and feelings, and this is when true theory of mind emerges. Children develop theory of mind skills in the following order[3][6][7][8]:

▪ Understanding “wanting” – Different people want different things, and to get what they want, people act in different ways.
▪ Understanding “thinking” – Different people have different, but potentially true, beliefs about the same thing. People’s actions are based on what they think is going to happen.
▪ Understanding that “seeing leads to knowing” – If you haven’t seen something, you don’t necessarily know about it (like the Dad in the example above on the telephone). If someone hasn’t seen something, they will need extra information to understand.
▪ Understanding “false beliefs” – Sometimes people believe things that are not true, and they act according to their beliefs, not according to what is really true.
▪ Understanding “hidden feelings” – People can feel a different emotion from the one they display.

When one child finally masters these tasks above, socialization will be easier for her, thus practicing her “theory of mind skills” at home, school and play until she has more than enough theory of mind to deal with people and life in general.

Image from Pinterest. Theory of Mind works like this picture. One person knows that the other person thinks about her.

What if a child has no theory of mind?

Like stated above , not all children have developed theory of mind especially if a child has autism or a learning disability. This makes them look like antisocial or without empathy leaving them socially isolated. This is what we call mind blindness.

What is mind blindness?

Mind blindness is a cognitive disorder where an individual is unable to attribute mental states to the self and other. As a result of this disorder the individual may be unaware of others’ mental states, or incapable in attributing beliefs and desires to others.[9][10] This means that a certain individual with mind blindness has little to no knowledge and understanding of oneself’s emotions as well as the emotions of others ie you cannot comprehend why you best friend cries over a movie character that has died towards the end of the story. Mind blindness is said to be common in autism spectrum disorders like the classic autism and Asperger’s syndrome, schizophrenia, and even depression, dementia and normal aging (that’s why your grandpa is grumpy sometimes).

Mind-blindness is a state where the ToM has not been developed or lost in an individual. The ToM is implicit in neurotypical individuals. This enables one to make automatic interpretations of events taking into consideration the mental states of people, their desires and beliefs.[9] Researcher Simon Baron-Cohen says that an individual lacking a ToM would perceive the world in a confusing and frightening manner; leading to a withdrawal from society.[9][11]

An alternative to the ToM deficit is that of impairment to read more complex emotions of people (sarcasm, figures of speech). Uta Frith concluded that the processing of complex cognitive emotions is impaired compared to simpler emotions.[12]

In short if you have mind blindness, you are dumb in recognizing and processing emotions of yourself and others, leaving you clueless on how to deal with other people. You will actually depend more on your logical mind to comprehend the world around you. As in my experience before when I was younger, I think like a robot or computer meaning I only have black and white, yes or no thinking. The result is I cannot understand what the other person says, thinks or feels like people are speaking a different language. This caused me to be socially isolated.

Let’s give some examples of situations where mind blindness is present:

Imagine that your friend cried over her dead cat. Of course for most of us that would be a very sad and horrible feeling when you lost your beloved pet knowing that she will never live again. But if you have mind blindness you can’t understand her emotions of grief over the death of her cat. You just might think it’s already dead and cannot come back. You either just ignore her feelings or even you can say why should you cry over a died living thing?

Here’s another situation. You are given by your date a bunch of roses. For most girls it’s really sweet and appropriate to be given flowers by a date to express his admiration and affection for you. But if you have mind blindness you may say why I was given dead plants?

Too bad. When you have mind blindness you do think very literally like a computer which just thinks only a yes/no command and if no it is error. No emotion. No gray areas. This makes a person with mind blindness look either aloof, antisocial or even rude to other people leading him to be socially isolated without ever knowing why. He’s totally clueless how to read people ‘intuitively’ without becoming ‘dry.’

What causes mind blindness?

Mind blindness is said to be caused by deficits in three regions of the brain[9] where ToM is utilized:

The anterior paracingulate cortex is the key region of mentalizing. This cortex is associated with the medial frontal cortex where activation is associated with the mentalization of states.[9][10]

The superior temporal sulcus and the temporal poles aid in the activation of the regions that are associated with the ToM. The superior temporal sulcus is involved in the processing of behavioural information while the temporal poles are involved in the retrieval of personal experiences. The temporal poles provide personal experiences for mentalization such as facial recognition, emotional memory and familiar voices.[9][10]

The amygdala and the orbitofrontal cortex also are a part of the ToM. It is in involved in the interpretation of behaviour which plays an important role in social cognition and therefore contributes to the theory of the mind.

Executive function also plays a role in ToM where it includes skills such as organizing, planning, sustaining attention, and inhibiting inappropriate responses.[]

Huh? Where in the brain they are?

A lot of regions in the brain are involved in ToM but mostly they are found in the frontal and temporal lobes of the cerebrum (the biggest part of the brain). The amygdala is not part of the cerebrum but it is part of the making of ToM and is within the temporal lobes as well.

The anterior paracingulate cortex is located above the anterior corpus callosum (the cingulate gyrus is the red area below while the corpus callosum is the white area below the gyrus) near the frontal lobe.

Image from studyblue.com

The superior temporal sulcus is in the middle portion of the brain on the temporal lobe while the temporal poles are at the ends of the temporal lobe. (Below images courtesy of Wikipedia)

 

 

The amygdala is a tiny thing under the frontal lobe and under the corpus callosum.

Image from brainmadesimple.com. Location of the amygdala

 

The orbitofrontal cortex is located in the most inferior part of the frontal lobe.

Image from Tufts University. The orbital frontal cortex is under the frontal cortex.

Damage or underdevelopment to these areas can cause mind blindness.

How is mind blindness tested?

When a child does not developed normally like having social deficits including no eye contact and non-responsiveness tests are given to rule out a developmental disability or deafness. If she has a suspected developmental disability psychological tests are given of which the most famous is the Sally-Ann(e) test[13].

(C) Psychology Today. Sally-Ann Test.

The image above asks where will Sally look for the ball. To be able to pass this test, the child must answer that Sally will look for the basket and not in the box. Below is the more detailed Sally-Ann(e) test including the answers:

(c) EducateAutism.com

If the child has a wrong answer she is now confirmed with mind blindness, a hallmark sign of autism disorder.

It is very important therefore to assess whether a child has developed ToM or not. This is to assess if her brain is developing typically or not. This is to ensure that proper care is utilized to the child and develop specific plans of therapy or lesson plan to the child whether with ToM or with mind blindness.

If someone is mind blind, how is it managed?

As soon as mind blindness is confirmed (usually with the diagnosis of autism/Asperger’s) , affected kids and teens  can learn to compensate for mindblindness and alexithymia with the parent’s help and a lifetime of constant counseling by therapists.[15]

To help a mind blind child (or teen ot adult) parents and/or therapists must understand that their Aspergers kids must be taught to use logic to make sense of the world and the people in it, one personal situation at a time.[15] This is to compensate for the child’s lack of social intelligence and to take advantage of his strength in his logical mind to be taught social skills and management of emotions literally as if they are academic subjects.

My Aspergers Child website has general tips of teaching ToM to people with mind blindness[15]:

1. Every human behavior has a reason behind it, even if I don’t see it.
2. Most people usually talk about the things they want, and openly say what they believe.
3. Some people are so messed up that it is just not possible to figure them out. Know when to give up.
4. When somebody’s behavior flies in the face of logic, concentrate on that person’s feelings.
5. Women talk more than men and focus on feelings more.

These are the more general tips. For more specific tips click on their article page here.

Conclusion

Theory of mind is an important tool for us in order to deal with the world. It enables us to navigate the social world, assess and recongnize our own feelings as well as the feelings and thinking of other people, and most of all enable us to cooperate with people as if they are our own family. However some people in neurodiversity lack ToM and therefore have mind blindness which can adversely affect their dealing with themselves as well as other people which could bring bad results such as social isolation and depression. It is therefore important that when a child shows lack of interest in the world to be assessed right away for mind blindness and help teach theory of mind through years of therapy and love and support. With enough support neurodiverse people can navigate the world more easily.

Reference:

1. https://en.m.wikipedia.org/wiki/Theory_of_mind
2. Premack, D. G.; Woodruff, G. (1978). “Does the chimpanzee have a theory of mind?”. Behavioral and Brain Sciences 1 (4): 515–526. doi:10.1017/S0140525X00076512
3. http://www.hanen.org/helpful-info/articles/tuning-in-to-others-how-young-children-develop.aspx
4. Westby, C. & Robinson, L. (2014). A developmental perspective for promoting theory of mind. Topics in Language Disorders, 34(4), 362-383.
5. de Villiers, J. G. & de Villiers, P. A. (2014). The role of language in theory of mind development. Topics in Language Disorders, 34(4), 313-328.
6. Sussman, F. (2006). TalkAbility™ – People skills for verbal children on the autism spectrum: A guide for parents. Toronto, ON: Hanen Early Language Program.
7. Wellman, H. M. & Liu, D. (2004). Scaling theory of mind tasks. Child Development, 75, 759-763.
8. Peterson, C. C., Wellman, H. M. & Slaughter, V. (2012). The mind behind the message: Advancing theory-of-mind scales for typically developing children, and those with deafness, autism, or asperger syndrome. Child Development, 83(2), 469-485.
9. https://en.m.wikipedia.org/wiki/Mind-blindness
10. Gallagher, Helen L.; Frith, Christopher D. (1 February 2003). “Functional imaging of ‘theory of mind'”. Trends in Cognitive Sciences 7 (2): 77–83. doi:10.1016/S1364-6613(02)00025-6. PMID 12584026.
11. Baron-Cohen, Simon (1990). “Autism: a specific cognitive disorder of ‘mind-blindness'”. International Review of Psychiatry 2: 81–90. doi:10.3109/09540269009028274.
12. Frith, Uta (1 December 2001). “Mind Blindness and the Brain in Autism” (PDF). Neuron 32 (6): 969–979. doi:10.1016/S0896-6273(01)00552-9. PMID 11754830. Retrieved 19 February 2012.
13. Baron-Cohen S, Leslie AM, Frith U (1985). “Does the autistic child have a ‘theory of mind’?” (PDF).Cognition 21 (1): 37–46. doi:10.1016/0010-0277(85)90022-8. PMID 2934210. Retrieved2008-02-16.
14. https://www.autismspeaks.org/family-services/tool-kits/asperger-syndrome-and-high-functioning-autism-tool-kit/executive-functioni
15. http://www.myaspergerschild.com/2011/04/coping-with-mind-blindness-and.html

Left-Handedness

Most of us know someone who uses her left hand for writing, feeding – in short – left hand dominant. While this is somewhat rare versus right-handed people like most of us, but sometimes we wonder why left-handedness occur (or why we have a dominant hand side like right-handed or left-handed).

But first let’s define handedness.

Handedness is a better (faster or more precise) performance or individual preference for use of a hand, known as the dominant hand.[1][2] This means each one of us has a dominant hand in doing skills like writing, playing an instrument, cooking, carrying a light object using one hand, feeding, etc. We can be either right-handed where our right hand is stronger or left-handed where our left hand is stronger. Some people can have both hands that are dominant i.e. can write legibly using both right and left hands – that is called ambixterity and some people can do tasks perfectly using one hand side and other tasks on the other hand side. These people have cross-handedness.

Handedness is the hand used for activities that require a lot of practice and fine motor skills (e.g. writing) or the coordination of large muscle groups to carry out smooth actions (e.g. throwing a ball), both of which are activities employing many neurons in the brain and requiring tightly concentrated and specialized neurological wiring.[3]

Aside from the four types of handedness mentioned above, another may be considered as a type of handedness though it can be more of a disability. It is called ambilevous (or ambisinistrous) handedness[3] where people have equally poor dexterity (are equally clumsy), with both hands. This is a very rare occurrence, usually resulting from a debilitating physical condition[3] like dysgraphia

Most people (90% of the world’s population) are right-handed with approximately 60% of people being strongly right-handed (performing ALL activities with the right hand).[3] Around 10% (possibly more) of the world’s population falls into this category, although only perhaps 3% are strongly left-handed (performing ALL activities with the left hand). Cross-dominant people are slightly more common at 35% while ambidextrous people are only 1% of the world’s population.

While right-handedness may be considered the”normal” type of handedness, much wonder is made why there are left-handed people and other hand dominances.

Image courtesy of learning4kids.net. This girl is right-handed. She uses her right hand to put the sring to the cylinder.

Why is there left-handedness?

Image courtesy of The Independent. This is a left-handed person. He uses his left hand to write.

Different theories present a reason for hand dominance. One is is called the Division of Labor theory where since people’s speaking and handiwork require fine motor skills, its presumption is that it would be more efficient to have one brain hemisphere do both, rather than having it divided up. Since in most people, the left side of the brain controls speaking, right-handedness predominates. This theory also predicts that left-handed people have a reversed brain division of labor.[1][4]

How is this?

We know that our brains has two hemispheres, the left and right. Each hemisphere controls every activity we do. In right-handed people verbal processing takes place in the left hemisphere, whereas visuospatial processing is mostly done in the opposite hemisphere. Left-handed individuals have a heterogeneous brain organization in which their brain hemisphere is either organized in the same way as right-handers (but with the hemispheres reversed) or even such that both hemispheres are used for verbal processing.[1][4]

In short right-handed people have their motor skills done in the right hemisphere and speech at the left hemisphere while left-handed people have their brains reversed that’s why their left hand is more dominant.

Genetics is an obvious factor. Chances are if one or both your parents or someone in your immediate family or relatives is left-handed you will be left-handed also.

Penatal exposure to a drug called diethylstilbestrol (a synthetic estrogen-based fertility drug) can be a contributing factor to left-handedness in males. A 2003 study endorsed by the Centers for Disease Control determine that males with in-utero exposure to this drug are more likely to be left-handed[1][5] than those who were not exposed to it.

Presentation of the baby’s head during last trimester of pregnancy can also determine handedness. About two-thirds of fetuses present with their left occiput (back of the head) at birth. This partly explains why prematurity results in a decrease in right-handedness. Previc argues that asymmetric prenatal positioning creates asymmetric stimulation of the vestibular system, which is involved in the development of handedness.[1] People with reduced right-handedness may have either delay or anomaly in their vestibular system.[1][6] This is called prenatal vestibular asymmetry.

Ultrasound can also contribute to left-handedness. It may affect the brains of unborn children, causing higher rates of left-handedness in children whose mothers received ultrasounds during pregnancy. Research on this topic suggests there may exist a weak association between ultrasound screening (sonography used to check on the healthy development of the fetus and mother during pregnancy) and non-right-handedness.[1][7]

How common are left-handed people and how they are in everyday life?

Since right-handedness is the common hand dominance, left-handed people find it quite difficult to adjust to the right-handed world. From classroom armchairs and spiral notebooks to vehicles with steering wheels at the right side, that presents some problems if you’re left-handed. Many objects like scissors can be a struggle for left-handed folks since scissors are usually made for the right-handed.[8] Even in socialization lefties (left-handed people in short, just my coined term) have some sort of a problem like when shaking hands or giving high fives[8] especially with a right-handed person.

Left-handed people are also stereotyped. In fact, a Psychology Today article explains some of the stereotypes lefties have. Left-handed people are thought to be intelligent.[9] There are anecdotal accounts of artists and musicians tending to be left-handed, an observation given wings by the overly simplistic notion that the right-hemisphere (which controls the left hand) is the seat of creativity.[9] But as psychologist Chris McManus explains in his award-winning book Right Hand Left Hand, “although there are recurrent claims of increased creativity in left-handers, there is very little to support the idea in the scientific literature.”[9]

Left-handed people also are said to have weaker immune system and die earlier.[9] But that is only based on a statistical research of left-handed athletes who have died young.[9] Like the myth of left-handed smartness, this theory is also a myth.

This is a fact. Left-handers are less likely to be left-hemisphere dominant for language.[9] In the vast majority of the population, language function is nearly always localised to the left hemisphere.[9] Among right-handers, left-sided dominance for language approaches upwards of 95 per cent prevalence. However, among left-handed people this drops to 70 per cent, with the others either having language localised to the right hemisphere, or spread evenly across both hemispheres.[9]

In terms of income, there is no clear correlation of left-handedness to salary. One study claimed that lefties earned 10 to 15% more than their right-handed counterparts.[1][10] But a 2014 US study  published by the National Bureau of Economic Research, Harvard economist Joshua Goodman finds that left-handed people earn 10 to 12 percent less over the course of their lives than right-handed people.[1]

Left-handers are said to be common interactive sports like tennis, badminton and cricket.[1] Fencing has a lot of left-handers.[1][11] And lefties have an advantage over right-handed people in these sports. How?

Here’s a quote from Wikipedia.

The advantage to players in one-on-one sports, such as tennis, boxing, fencing or judo, is that, in a population containing perhaps 10% left-handers and 90% right-handers, the left-hander plays 90% of his or her games against right-handed opponents and is well-practiced at dealing with this asymmetry. Right-handers play 90% of their games against other right-handers. Thus, when confronted with left-handers, they are less practiced. When two left-handers compete against each other, they are both likely to be at the same level of practice as when right-handers play other right-handers. This explains why a disproportionately high number of left-handers are found in sports in which direct one-on-one action predominates.[1]

Image courtesy of mirror.co.uk. Rafael Nadal is an example of a left-handed tennis player.

When it comes to distribution among genders, left-handedness is said to be more common in homosexuals and asexuals (people who have no sexual preference or never become attracted to any person in a romantic or sexual way).[1]

Left-handedness is also common among sexual paraphilias (people with uncommon way of sexual arousal like fetishes or sadomasochism).[1]

If this is so, why is there discrimination to left-handed people?

Because of the presentation that left-handers have, they usually face more discrimination especially in the past. They are discriminated the way autistics, slaves, and women were discriminated before. Many tools and procedures are designed to facilitate use by right-handed people, often without even realizing difficulties placed on the left-handed. John W. Santrock has written, “For centuries, left-handers have suffered unfair discrimination in a world designed for right-handers.”[1][12]

Before Industrial Revolution (when modern technology started to develop), all tools are made for right-handed people without consideration for left-handed people. Writing before was made for right-handers also using ink blot pens. When ink blot is used with left hand, stains and blotches occur[1], making the left handers more clumsy and inadequate making them prejudiced for a long time.

Languages do also refer left as wrong and right as right. Wikipedia quotes the following paragraph regarding repressing left.[1]

Moreover, apart from inconvenience, left-handed people have been considered unlucky or even malicious for their difference by the right-handed majority. In many European languages, including English, the word for the direction “right” also means “correct” or “proper”. Throughout history, being left-handed was considered negative.[1]

In French, gauche means both “left” and “awkward” or “clumsy”, while droit(e) (cognate to English direct and related to “adroit”) means both “right” and “straight”, as well as “law” and the legal sense of “right”. The name “Dexter” derives from the Latin for “right”, as does the word “dexterity” meaning manual skill. As these are all very old words, they would tend to support theories indicating that the predominance of right-handedness is an extremely old phenomenon.

That is really discriminating though. The worse is left-handedness was associated with black magic (witchcraft) hence called left-hand path.[1][13]

Discrimination still exists up to this day, but let us remember that left-handed people are just a variation of hand dominance just like variation of hair color like blonde or black.

Left-handedness Advantage

Nevertheless, being left-handed has advantages do like being good at sports stated above. Aside from this some more advantages of being left-handed are enumerated below[14]:

Lefties have a greater chance of being a genius- or having a high IQ. Researchers aren’t sure why, but those who are left handed seem to make up a disproportionately large part of those who are highly intelligent. For example, twenty percent of all Mensa members are left-handed.[14]

Left handed people adjust more easily to seeing underwater. Bizarre as it may sound, one of the benefits of being left handed is being able to adjust more easily to see the world around you when you’re underwater. While you may not need this ability very often, it could come in handy if you live by the sea or enjoy swimming.[14

(C) Disney. Does Sebastian think of Ariel as left-handed?

Lefties are better able to multitask. One of the advantages of being left-handed is that it forces your brain to think more quickly. What this means for everyday life is that those who are lefties may find it easier to multi-task and deal with a large, sometimes unorganized stream of information.[14]

More advantages of left-handers are some of them have sharper memories, left-handed stroke patients are able to survive more than their right-handed counterparts, and also they are better in playing video games.[14] The reason is not so known but maybe because  lefties need to train both their left and right brain hemispheres, which means more brain power.

Left-handed people are also visual thinkers making ideal for an artistic occupation[14] like in arts programs.

Can left-handedness be part of neurodiversity?

Yes. Just like dyslexia and Asperger’s syndrome, left-handedness is just another brain outcome representation and absolutely not a malady that needs to be corrected. After all, left-handedness add color to human brain variety.

Reference:

1. https://en.wikipedia.org/wiki/Handedness
2. Holder, M.K. What does Handedness have to do with Brain Lateralization (and who cares?). Retrieved 11 August 2012.
3. http://www.rightleftrightwrong.com/what.html
4. Banich, Marie (1997). Neuropsychology: The Neural Bases of Mental Function.
5. Titus-Ernstoff, L. (2003). “Psychosexual Characteristics of Men and Women Exposed Prenatally to Diethylstilbestrol”. CDC.
6. Nonright-handedness, central nervous system and related pathology, and its lateralization: A reformulation and synthesis.
7. Salvesen, K. Å. (1 September 2011). “Ultrasound in pregnancy and non-right handedness: meta-analysis of randomized trials”. Ultrasound in Obstetrics & Gynecology 38 (3): 267–271. doi:10.1002/uog.9055.
8. http://www.huffingtonpost.co.uk/2014/08/13/lefthanded-problems_n_5674374.html
9. https://www.psychologytoday.com/blog/brain-myths/201303/three-myths-and-three-facts-about-left-handers
10. Waldfogel, Joel (August 16, 2006). “Sinister and Rich: The evidence that lefties earn more”. Slate
11. Diana Widermann, Robert A. Barton, and Russel A. Hill. Evolutionary perspectives on sport and competition. In Roberts, S. C. (2011). Roberts, S. Craig, ed. “Applied Evolutionary Psychology”. Oxford University Press.doi:10.1093/acprof:oso/9780199586073.001.0001.ISBN 9780199586073.
12. Santrock, John W. (2008). Motor, Sensory, and Perceptual Development. Mike Ryan [Ed.], A Topical Approach to Life-Span Development(pgs.172–205). Boston, MA: McGraw-Hill Higher Education.
13. https://en.wikipedia.org/wiki/Left-hand_path_and_right-hand_path
14. http://www.anythinglefthanded.co.uk/being-lh/lh-info/advantages.html#sthash.I43eZA0j.dpbs