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.”
IS AtD-ANGLE A RELIABLE MARKER FOR IQ?
 
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.