A child sucks her thumb as she attends a "Get Your Knee Off My Neck" march and rally outside Trump Tower in the Manhattan borough of New York City, New York, U.S., July 31, 2020. REUTERS/Carlo Allegri 

Cricket - ICC Cricket World Cup - England v India - Edgbaston, Birmingham, Britain - June 30, 2019 India's MS Dhoni spits out blood after sucking his cut thumb Action Images via Reuters/Andrew Boyers 

Cricket - ICC Cricket World Cup - England v India - Edgbaston, Birmingham, Britain - June 30, 2019 India's MS Dhoni sucks his thumb after it was hit Action Images via Reuters/Andrew Boyers 

A young girl sucks her thumb as people participate in a yoga class during an annual Solstice event in the Times Square district of New York, U.S., June 21, 2017. REUTERS/Lucas Jackson 

A young girl sucks her thumb as people participate in a yoga class during an annual Solstice event in the Times Square district of New York, U.S., June 21, 2017. REUTERS/Lucas Jackson 

A youth sits on a bench with his friends as he sucks his thumb while waiting for a ferry in the Staten Island borough of New York City, New York, U.S. June 2, 2017. REUTERS/Carlo Allegri 

Ismael Blanco, 6, a neurological patient being treated with anticonvulsants, sucks his thumb while he sleeps during an electroencephalogram in a clinic in La Guaira, Venezuela February 4, 2017. REUTERS/Carlos Garcia Rawlins SEARCH "EPILEPSY CARACAS" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. TPX IMAGES OF THE DAY 

Football Soccer - Brighton & Hove Albion v Bolton Wanderers - Sky Bet Football League Championship - The American Express Community Stadium - 15/16 - 13/2/16
Jamie Murphy celebrates after scoring the first goal for Brighton
Mandatory Credit: Action Images / David Field

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Mo Farah of Britain reacts after winning the men's 5000m event during the 15th IAAF World Championships at the National Stadium in Beijing, China August 29, 2015. REUTERS/Lucy Nicholson

Mo Farah of Britain reacts after winning the men's 5000m event during the 15th IAAF World Championships at the National Stadium in Beijing, China August 29, 2015. REUTERS/Lucy Nicholson

Argentina's Lionel Messi sucks his thumb to celebrate after scoring a goal during the 2014 World Cup Group F soccer match between Argentina and Iran at the the Mineirao stadium in Belo Horizonte June 21, 2014. REUTERS/Sergio Perez (BRAZIL - Tags: TPX IMAGES OF THE DAY SOCCER SPORT WORLD CUP)

Argentina's Lionel Messi sucks his thumb to celebrate after scoring a goal during the 2014 World Cup Group F soccer match between Argentina and Iran at the the Mineirao stadium in Belo Horizonte June 21, 2014. REUTERS/Sergio Perez (BRAZIL - Tags: TPX IMAGES OF THE DAY SOCCER SPORT WORLD CUP)

Costa Rica's Joel Campbell celebrates with the match ball after scoring against Uruguay during their 2014 World Cup Group D soccer match at the Castelao stadium in Fortaleza June 14, 2014. REUTERS/Dominic Ebenbichler (BRAZIL - Tags: TPX IMAGES OF THE DAY SOCCER SPORT WORLD CUP) TOPCUP 

A boy sucks his thumb next to his mother during a demonstration outside of the United Nations, asking for an independence referendum for the region of Abyei to choose whether it wants to be part of Sudan or South Sudan, in New York, September 23, 2013. REUTERS/Lucas Jackson (UNITED STATES - Tags: CIVIL UNREST POLITICS) 

Four-year-old Niuniu, who has late-stage neuroblastoma, a malignant cancer of the nervous system, sucks on his thumb while resting at their temporary apartment in Shanghai, May 28, 2013. China has massively ramped up spending on health care, but many millions of people still cannot afford even basic health care, and health insurance schemes run by the government have only patchy coverage. Picture taken May 28, 2013. REUTERS/Aly Song (CHINA - Tags: HEALTH) 

A girl plays at the "Guidepost to New Space" installation by Japanese artist Yayoi Kusama at her exhibition titled "Yayoi Kusama - Obsessions" at the Japan Culture Foundation in Hanoi May 27, 2013. The exhibition is the first one held in Vietnam for Kusama, who is known as the "polka dot queen of avant garde art". It runs till July 28 as part of 40th anniversary celebrations of the establishment of the diplomatic relations between Vietnam and Japan. REUTERS/Kham (VIETNAM - Tags: SOCIETY TPX IMAGES OF THE DAY POLITICS ANNIVERSARY) 

A Palestinian woman holds her child as they wait to cross into Egypt, at the Rafah border crossing in the southern Gaza Strip May 22, 2013. The Rafah crossing between Gaza and Egypt - closed for five days by border Egyptian security officers angered at a kidnapping - was reopened early on Wednesday. Two of the captives had worked at the crossing. REUTERS/Ibraheem Abu Mustafa (GAZA - Tags: POLITICS) 

Venezuela's Jose Salomon Rondon sucks his thumb as he celebrates his team's first goal against Paraguay during their 2014 World Cup qualifying soccer match in Asuncion September 11, 2012. REUTERS/Jorge Adorno (PARAGUAY - Tags: SPORT SOCCER) 

A girl sleeps under a mosquito net surrounded by her family's belongings after a fire swept through a slum community in Quezon City, Metro Manila November 20, 2011. The fire of unknown origin destroyed hundreds of homes, killed at least one person and left some 1,500 families homeless, local media reported. REUTERS/Cheryl Ravelo (PHILIPPINES - Tags: DISASTER SOCIETY) 

Jefferson Farfan (C) of Schalke 04 sucks his thumb as he celebrates his goal during their Champions League round of 16 second leg soccer match against Valencia in Gelsenkirchen, March 9, 2011. REUTERS/Kai Pfaffenbach (GERMANY - Tags: SPORT SOCCER) 

Real Madrid's Cristiano Ronaldo celebrates his goal during their Spanish first division soccer league match against Getafe at Colisseum Alfonso Perez stadium in Madrid January 3, 2011. REUTERS/Juan Medina (SPAIN - Tags: SPORT SOCCER) 

A Kashmiri Muslim girl leans against a pillar during Friday prayers inside 500-year-old Jamia Masjid in Srinagar June 11, 2010. REUTERS/Fayaz Kabli (INDIAN-ADMINISTERD KASHMIR - Tags: RELIGION) 

Haitians wait in line after arriving at Veracruz port onboard a Mexican navy ship April 25, 2010. The family reunification program of Mexico's migration institute has reached a total of 324 Haitians who migrated after the earthquake in January, local media reported. Their FM3 migratory forms allow them to work, study, travel by country, enter and exit, as well as give them access to public services. REUTERS/Martin Lara Reyna (MEXICO - Tags: POLITICS SOCIETY) 

Napoli's Marek Hamsik celebrates after scoring his second goal against Juventus during their Italian Serie A soccer match at the Olympic stadium in Turin October 31, 2009. REUTERS/Giampiero Sposito (ITALY SPORT SOCCER IMAGES OF THE DAY) 

Arsenal's Robin Van Persie celebrates his 2nd goal against Tottenham Hotspur during their English Premier League soccer match at the Emirates Stadium in London October 31, 2009. REUTERS/ Eddie Keogh (BRITAIN SPORT SOCCER IMAGES OF THE DAY) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. NO USE WITH UNAUTHORIZED AUDIO, VIDEO, DATA, FIXTURE LISTS, CLUB/LEAGUE LOGOS OR "LIVE" SERVICES. ONLINE IN-MATCH USE LIMITED TO 45 IMAGES, NO VIDEO EMULATION. NO USE IN BETTING, GAMES OR SINGLE CLUB/LEAGUE/PLAYER PUBLICATIONS 

Espanyol's Ivan Alonso celebrates a goal against Tenerife during their Spanish first division soccer match at Cornella-El Prat stadium, near Barcelona, October 18, 2009. REUTERS/Albert Gea (SPAIN SPORT SOCCER IMAGES OF THE DAY) 

Atletico Madrid's Maxi Rodriguez sucks his thumb in celebration after scoring against Panathinaikos during their Champions League qualifying play-off first leg soccer match in Athens August 19, 2009. REUTERS/Yiorgos Karahalis (GREECE SPORT SOCCER) 

An internally displaced girl, who fled a military offensive in the Swat valley region, takes shelter under her sister's shawl while standing outside her family tent at the UNHCR (United Nations High Commission for Refugees) Sheik Shahzad camp in Mardan district, about 160 km (99 miles) northwest of Pakistan's capital Islamabad, June 15, 2009. REUTERS/Akhtar Soomro (PAKISTAN CONFLICT POLITICS SOCIETY) 

AS Roma's Francesco Totti celebrates after scoring against Bordeaux during their Champions League soccer match at the Olympic stadium in Rome December 9, 2008. REUTERS/Max Rossi (ITALY) 

AS Roma's Francesco Totti celebrates after scoring against Bordeaux during their Champions League soccer match at the Olympic stadium in Rome December 9, 2008. REUTERS/Max Rossi (ITALY) 

Rapid Vienna's Nikica Jelavic reacts after scoring against Altach during their Austrian league soccer match in Vienna November 8, 2008. REUTERS/Robert Zolles (AUSTRIA) 

Manchester City's Robinho celebrates scoring against FC Twente during their UEFA Cup soccer match at Eastlands stadium in Manchester November 6, 2008. REUTERS/Nigel Roddis (BRITAIN) 

Brazil's Robinho celebrates after scoring against Venezuela during their 2010 World Cup qualifying soccer match in San Cristobal October 12, 2008. REUTERS/Juan Carlos Hernandez (VENEZUELA) 

Aidan Ahlers, 3, leans out the window as his father, Doug drives a truck in the homecoming parade along Main Street in Grapevine, Texas October 9, 2008. REUTERS/Jessica Rinaldi (UNITED STATES) 

Brazil's Robinho sucks his thumb as he celebrates after scoring their second goal against Chile during their World Cup qualifying soccer match in Santiago September 7, 2008. REUTERS/Eliseo Fernandez (CHILE) 

A woman holds an infant wearing a bandana which reads 'liberate the country,' on the sixth day of a protest at the Government House in Bangkok August 31, 2008. More than 1,000 government supporters rallied outside Thailand's parliament on Sunday as lawmakers debated a street campaign threatening to topple Prime Minister Samak Sundaravej. REUTERS/Kham (THAILAND) 

Argentina's Sergio Aguero celebrates his goal against Brazil during their men's semi-final soccer match in the Worker's Stadium at the Beijing 2008 Olympic Games August 19, 2008. REUTERS/Sergio Moraes (CHINA) 

Kent Stonehocker of Calgary competes in the National Cannonball Championship in Toronto, August 13, 2008. REUTERS/Mark Blinch (CANADA) 

An Obama supporter sucks his thumb during a campaign rally at the Downingtown Station near Philadelphia, Pennsylvania, April 19, 2008. REUTERS/Tim Shaffer (UNITED STATES) US PRESIDENTIAL ELECTION CAMPAIGN 2008 (USA) 

A child holds a poster while waiting on former Scottish politician Tommy Sheridan and his wife Gail to arrive at Edinburgh Sheriff Court, central Scotland, to face perjury charges March 27, 2008. The couple were facing the charges after a police investigation into the evidence they gave during their defamation court case against the News Of The World newspaper. REUTERS/David Moir (BRITAIN) 

AS Roma's Francesco Totti (L) celebrates with his team mate Alberto Aquilani after scoring a penalty during their Italian Serie A soccer match against Napoli at the San Paolo stadium in Naples March 9, 2008. REUTERS/Max Rossi (ITALY) 

Real Madrid's Robinho celebrates his goal against Werder Bremen during their Champions League Group C soccer match at the Weser stadium in Bremen November 28, 2007. REUTERS/Christian Charisius (GERMANY) 

Real Madrid's Robinho celebrates his goal against Mallorca during their Spanish first division soccer match at the Santiago Bernabeu stadium in Madrid November 11, 2007. REUTERS/Victor Fraile (Spain) 

A girl sucks her thumb during a service of remembrance for Armistice Day at the Armed Forces memorial in the National Arboretum in Alrewas, central England November 11, 2007. REUTERS/Darren Staples (BRITAIN) 

A girl sucks her thumb during a service of remembrance for Armistice Day at the Armed Forces memorial in the National Arboretum in Alrewas, central England November 11, 2007. REUTERS/Darren Staples (BRITAIN) 

Real Madrid's Robinho celebrates his goal against Valencia during their Spanish first division soccer match at the Mestalla stadium in Valencia October 31, 2007. REUTERS/Victor Fraile (SPAIN) 

Real Madrid's Robinho celebrates his goal against Valencia with his team-mate Jose Maria Gutierrez during their Spanish first division soccer match in Valencia October 31, 2007. REUTERS/Victor Fraile (SPAIN) 

Children wait for the start of a mass baptism in Manila Cathedral August 21, 2007. Organizers said they expected more than 5,000 children from poor families to be baptised as Catholics in the ceremony sponsored by a former politician. REUTERS/Darren Whiteside (PHILIPPINES) 

A chimpanzee rests in its enclosure at a zoological park in the northern Indian city of Lucknow August 17, 2007. REUTERS/Pawan Kumar (INDIA) 

Two months and three days old white tiger cub Gullu sucks the thumb of its attendant at Chhatbir zoo in the northern Indian state of Punjab June 9, 2007. Gullu was rejected by its mother Shanti at birth but now has started taking liquids, the attendant said. REUTERS/Ajay Verma (INDIA) 

An indigenous Embera Wounaan child sucks his thumb in Santa Fe in the southern Darien province, on the border with Colombia, April 27, 2007. Panama's President Martin Torrijos visited Santa Fe to listen to the villagers' complaints, while giving them titles to their land and $35 to each family a month for food. The villagers said that Colombian guerrillas are recruiting them to shop for the guerrillas, leading the Panamanian police to try and control the amount of groceries being purchased. They also said that legitimate shopping is being confiscated, causing some families to have not enough to eat. REUTERS/Alberto Lowe (PANAMA) 

Yoshifumi Inao, a dancer in Israel's Batsheva Dance Company, performs part of a routine in 'Telophaza' during a media call for the company at a theatre in Sydney January 5, 2007, ahead of the three-week-long Sydney Festival. REUTERS/Will Burgess (AUSTRALIA) 

-PHOTO TAKEN 15JUN06-
An ape sits on a pole sucking its thumb at a sanctuary outside Madrid June 15, 2006. Spain's parliament is set to declare support for the rights to life and freedom for great apes in what will apparently be the first time any national legislature has recognised such rights for non-humans. Picture taken on June 15, 2006. 

An ape sits on a pole sucking its thumb at a sanctuary outside Madrid June 15, 2006. Spain's parliament is set to declare support for the rights to life and freedom for great apes in what will apparently be the first time any national legislature has recognised such rights for non-humans. Picture taken on June 15, 2006. REUTERS/Susana Vera (SPAIN) 

AS Roma's Francesco Totti celebrates by sucking his thumb after scoring against Livorno during their Italian Serie A soccer match at the Olympic stadium in Rome January 29, 2006. REUTERS/Tony Gentile 

Surrogate Squirrel Monkey mother Louise Grossfeldt looks at baby Loki which sucks its thumb after feeding time at Taronga Zoo in Sydney January 19, 2006. Primate expert Grossfeldt has been hand rearing the baby monkey since the mother died shortly after giving birth. Squirrel Monkeys, native to South America, are not endangered but are threatened by deforestation and are captured as part of the pet trade and for medical research. 

Surrogate Squirrel Monkey mother Louise Grossfeldt looks at baby Loki which sucks its thumb after feeding time at Taronga Zoo in Sydney January 19, 2006. Primate expert Grossfeldt has been hand rearing the baby monkey since the mother died shortly after giving birth. Squirrel Monkeys, native to South America, are not endangered but are threatened by deforestation and are captured as part of the pet trade and for medical research. REUTERS/Will Burgess 

Olympique Lyon's Cris (R) sucks his thumb after scoring against Troyes during their French Ligue 1 soccer match at the Gerland stadium in Lyon November 19, 2005. REUTERS/Robert Pratta 

A young girl sucks on her thumb as her friend plants tomato seeds in a greenhouse at Natzarim Settlement in the Gaza Strip August 8, 2005. Israel pressed ahead on Monday with preparations for its pullout from Gaza, signalling business as usual despite [Finance Minister Benjamin Netanyahu's] resignation in protest at the plan. 

A young girl sucks on her thumb as her friend plants tomato seeds in a greenhouse at Natzarim Settlement in the Gaza Strip August 8, 2005. Israel pressed ahead on Monday with preparations for its pullout from Gaza, signalling business as usual despite Finance Minister Benjamin Netanyahu's resignation in protest at the plan. REUTERS/Dan Balilty PA/FA