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Facial expressions may be inherited: study

Oct. 16, 2006
Courtesy PNAS
and World Science staff

Blind peo­ple dis­play si­m­i­lar fa­cial ex­pres­sions as their rel­a­tives, pro­vid­ing ev­i­dence that some fa­cial ex­pres­sions might be he­red­i­tar­y, re­search­ers have found.

Si­m­i­lar fa­cial move­ments in born-blind par­tic­i­pants (Left) and their sight­ed rel­a­tives (Right). (Cour­te­sy PNAS)

While the ex­pres­sions that con­vey emo­tion are uni­ver­sal, in­di­vid­u­al peo­ple dif­fer in the move­ments of their fa­cial mus­cles, cre­at­ing a dis­tinct fa­cial “sig­na­ture,” the sci­en­t­ists said.

To see whether these sig­na­tures might be her­it­a­ble, Gi­li Pe­leg at the Uni­ver­si­ty of Hai­fa, Is­ra­el, and col­leagues con­duc­t­ed tests on con­gen­i­t­al­ly blind peo­ple and their fam­i­ly mem­bers. 

Since the blind would not be able to see and mi­m­ic their rel­a­tives, all their move­ments would arise in­nate­ly, the sci­en­tists rea­soned. Dur­ing in­ter­views, they ex­am­ined the fre­quen­cy and man­ner­isms of move­ments for six emo­tio­nal states: an­ger, sad­ness, joy, dis­gust, sur­prise, and con­cen­tra­tion. 

The ex­pres­sions of the blind were more si­m­i­lar to fa­m­i­ly mem­bers than to stran­gers, the in­ves­ti­ga­tors found. This was es­pe­cial­ly for the ne­g­a­tive emo­tions that re­quire more de­tailed mus­cle move­ments, they ad­ded. 

The re­search­ers noted that oth­er com­po­nents of ex­pres­sion such as tim­ing and in­ten­si­ty were not ex­am­ined, but said their re­sults show re­lat­ed in­di­vid­u­als may each share a fa­mil­ial fa­cial ex­pres­sion sig­na­ture. 

The find­ings could lead to un­der­stand­ing the ge­net­ics be­hind fa­cial move­ments and con­di­tions such as au­tism, in which such move­ments are im­paired, Pe­leg and col­leagues said.

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Blind people display similar facial expressions as their relatives, providing evidence that some facial expressions might be hereditary, researchers have found. While the expressions that convey emotion are universal, individual people differ in the movements of their facial muscles, creating a distinct facial “signature,” the scientists said. To examine if these signatures might be a heritable trait, Gili Peleg at the University of Haifa, Israel, and colleagues conducted tests on congenitally blind people and their family members. Since the blind would not be able to see and mimic their relatives, all their movements would arise innately, the scientists reasoned. During interviews, they examined the frequency and mannerisms of movements for six emotional states: anger, sadness, joy, disgust, surprise, and concentration. The facial expressions of the blind subjects were more similar to family members than strangers, especially for the negative emotions that require more detailed muscle movements. The researchers note other components of expression such as timing and intensity were not examined, but their results provide some proof that related individuals may each share a familial facial expression signature. These findings could lead to understanding the genetics behind facial movements and conditions such as autism, in which such movements are impaired, Peleg and colleagues said.