Dr Oz: 'left-handed people are smarter'

Are left-handed people smarter than right-handed people?

“Well, in a way, left-handed people are smarter, and I’ll tell you why,” Dr. Oz says. “Left-handed people can deal with more incoming information that doesn’t come in an organized way.” Dr. Oz says this is because of the way the brain develops when a baby is in its mother’s womb. “The left brain normally controls your right side, which is really powerful,” he says. [In left-handed people], it allows the other side, the right brain, to become an equal partner.”

Because left-handed people can use both sides of their brain more readily, Dr. Oz says, they can process information coming into their brain in different ways more easily. “That’s why athletes do so well when they’re left-handed. And there are a lot of presidents who have been left-handed, and there are a lot of folks who, because they can deal with a lot of complicated issues at once, work pretty effectively,” he says.

But Dr. Oz says although you may write with one hand, parts of the body on the other side—such as an eye—can still be dominant. To determine which eye is dominant, Dr. Oz says to cut a pencil-sized hole in a piece of paper and hold it away from your face. Look through the hole at an object using only your right eye, then only your left. Dr. Oz says whichever eye you can still see the object through the hole with is your dominant eye.

Dr. Oz says many people are dominant with one eye and dominant with the opposite hand. “There are lots of different reasons you want to know [which eye is dominant]. If you were playing sports, it’s sort of helpful,” he says. “But folks actually use their different parts of their brain very differently, and it’s sort of cool to understand how it all comes up.”


While left-handedness (ranging from moderate through strongly left-handed) is found in approximately 10% of the population

• Four out of five (80%) original Macintosh computer designers were left handed;

• Five out of the last seven (71%) US presidents were left handed (Barack Obama’s runner-up – senator John McCain – is also a lefty);

• One out of four (25%) Apollo astronauts – who were all selected e.g. by their high intelligence – was left handed;

Mensa International  (the largest and oldest high-IQ society in the world) claims that 20% of their members are left handed;

• A 1988 study reported: 16.9% of 266 United States Chess Federation players being left-handed or ambidextrous (included in the sample were e.g. 138 male Chess Masters, 18.1% was left-handed or ambidextrous).

This is how to measure the dermatoglyphic AtD-angle

Most people are aware that they have fingerprints. But few people are aware of the likewise dermatoglyphic features in their palms. One of the most interesting characteristics of the palmar dermatoglyphics concerns the so-called AtD-angle: which concerns the angle between the a- triradius (under the index finger), the axial triradius (near the wrist), and the d-triradius (under the pinky finger).

The AtD-angle is e.g. known for it’s significance in Down syndrome (trisomy 21): most people who have Down syndrome have an AtD angle > 57o (80%), while in healthy people this characteristic is far less common (7%). But quite a few other trisomy syndromes are featured: see the picture below.
Interestingly, beyond the trisomy studies, a few other studies have indicated that the AtD-angle provides a significant clue about intelligence.

A 2010 STUDY:

Exactly one year ago a study from India reports:
Significant difference in the total t’ angle of the left palm was observed between mentally retarded patients and control group.Atd angle varied form 30o to 65o in normal individuals, where as in case of mental retardation < 30o to > 65o angle variationwas observed.

A 1980 STUDY:

And the significance of a small AtD-angle as a marker for high intelligence was e.g. confirmed in a 1980 study from Zagreb (former Yugoslavia), which reports:
“The atd angle and FRC1 of both hands in males and females are the main discriminators for classification results of canonical discriminant analysis, for more than 80% of the tested persons.”
While the AtD-angle is included in the Dermatoglyphic Multiple Intelligence Test (DMIT), the mentioned studies clearly indicate that in isolation the AtD-angle can not be used as a reliable marker for IQ – simply because the AtD-angle highly varies among the individuals of various IQ populations.
At a later stage (hopefully in 2011) a new palmar dermatoglyphic marker will be introduced – based on the ‘configuration shape’ of four palmar triradii. Early results indicate that this new marker represents a more reliable marker for Down syndrome (compared to the AtD-angle) … and when combined with the major palmar lines it appears to provide a significant clue for IQ!
The picture below provides an overview of the major dermatoglyphic markers in the palm and fingers.

Just another concept of how various types IQ could relate to the fingers...?

The previous post introduced Dermatoglyphics Multiple Intelligence Test (DMIT) – which e.g. describes how various aspects of intelligence could relate to the 10 individual fingers & the brain lobes. Unfortunately there appears to be no (academic) scientific evidence available which confirms the validity of the DMIT-model. But there appears to be multiple evidence available which does confirm that various hand features do provide clues to the general intelligence – specified to the intelligence quotient (IQ)!

In the next 3 posts a quick introduction to how various hand dimensions correlate with IQ, starting with: hand shape.


The two most common causes of a mental retardation (Down syndrome + fragile X-sydrome) are typically featured with relatively broad palm. This typically results in a high ‘hand index’: > 47. 

NOTICE: The ‘hand index’ is defined as: 100 x the quotient of the palm width and the hand length. A ‘hand index’ of 0.47 or higher could be described as high, because far most international ‘hand index’ studies so far indicate that the average varies from 42 to 0.46 (Japanese males: 43.1, American males: 46; Japanese females: 42.3, American females: 43.7). 

So, one could expect that a low ‘hand index’ could provide a clue to a high IQ. But one should be very aware of the fact that the ‘hand index’ varies among men (higher) and women (lower), and among ethnic populations (lower in asians, higher in caucasians).

Interestingly… a 1980 Zagreb study on a large sample of males (N=540) has pointed out that ‘hand width’ does correlate negative with IQ (confirmed at all 10 IQ measures involved in the study). The study also reported that ‘hand length’ did not correlate with IQ – some of the dimensions produced very small positive correlations, which raises the question whether ‘hand index’ would have produced more signficant results than ‘hand width’.

NOTICE: The 1980 study also reveal that all 10 IQ measures produced positive correlations which ‘body height’ – a result which has been confirmed by many studies.

The picture below demonstrates how to measure ‘hand width’: in scientific studies this is always done at the position of the metacarpals (0ne could use the starting point of the life line as an easy identifyable point of reference).

And hand length is measure from the distal wrist crease to the tip of the middle finger. 

In 1983 American developmental psychologist Dr. Howard Gardner argued that the concept of intelligence as traditionally defined in psychometrics (IQ tests) does not sufficiently describe the wide variety of cognitive abilities humans display. His theory became know under the name ‘Multiple Intelligence’ (MI). A few years ago a rather remarkable commercial spin-off from Gardner’s theory became available: a product named the DMIT, which stands for: ‘Dermatoglyphics Multiple Intelligence Test’.

The origins of the DMIT test were developed in Taiwan,  and became available in various Asian countries as a franchise product. The product claims to be a scientific product focussed on assessing the ‘multiple intelligences’ of young children. Basically, the product suggests that one can assess Gardner’s multiple intelligences via the 10 fingerprints of your hand. And the assumption is made that each finger is connected with the 5 brain lobes of the hemispheres (see the picture below).

Is the DMIT a valid test?

So far there appears to be no public research available to answer this question – though an intelligent reader could recognize from this point solely a clue about the nature of this so-called ‘scientific test’. 

By the way, Gardner’s theory describes only eight basic types of intelligence to date – though without claiming that this is a complete list. Gardner’s original list included only seven of these, but in 1999 he added a naturalist intelligence. He has also considered existential intelligence and moral intelligence, but does not find sufficient evidence for these based upon his articulated criteria.

Howard Garnder’s ‘multiple intelligences’:

More detailed considerations + links to GeneCode & ThumbRule DMIT websites are available at the Modern Hand Reading Forum:

IQ TEST: Does your intelligence correlate with your fingerprints & dermatoglyphics?