A photographer tested the concentration of several pairs of dogs as he captured their reactions to treat time in a series of shots. Christian Vieler, 47, of Waltrop, Germany, has been a professional dog photographer since 2016. He came up with the idea of snapping two dogs catching treats simultaneously. Here: Basset Hounds. (Photo by Vieler Photography/Caters News Agency)

Kathleen Darling, wife of disabled veteran Caleb Darling, celebrates a shot during a sled hockey game on March 29, 2012 in Aspen, Colorado. (Photo by John Moore/Getty Images)

An F/A-18 Hornet assigned to Strike Fighter Squadron One Five One (VFA-151) emerges from a cloud created when it broke the sound barrier in the skies over the Pacific Ocean, July 7, 1999. (Photo by John Gay/US Navy)

Scores of internally displaced Muslims are at the heart of the humanitarian crisis in Central African Republic, where violence between Christians and Muslims has threatened to spiral into genocide. Photo: An internally displaced woman carries her child in a camp for internally displaced people (IDPs), located at Bangui International Airport, April 10, 2014. (Photo by Goran Tomasevic/Reuters)

Girls play with their new dolls during the distribution of free toys for low-income families and a picture on the lap of one of the Three Wise Men at Almudena Cathedral in Madrid, Spain, December 22, 2015. Traditionally, children in Spain receive their presents delivered by the Three Wise Men on the morning of January 6 during the Christian holiday of the Epiphany. (Photo by Susana Vera/Reuters)

Accused Nazi criminal John Demjanjuk wears sunglasses as he arrives for his trial at a court room prior to the assumed verdict on May 12, 2011 in Munich, Germany. (Photo by Johannes Simon/Getty Images)

Anne Hathaway arrives for the premiere of Twentieth Century Fox & Blue Sky Studios' “RIO” on April 10, 2011 in Hollywood, California. (Photo by John Sciulli/Getty Images)

Syrian President Bashar Al Assad watches as Pope John Paul II boards his plane at Damascus airport May 8, 2001 at the end of the Pontiff's four-day visit to Syria.