The miners, he said, need to be compensated for the loss of daylight, both in the vitamin D they are missing and in the "sleep-waking" routine that's been interrupted.
"We've been impressed with the planning, quality of healthcare, compassion and support provided to the miners and their families," said Duncan, who is a physician. "All the world is hoping this will be successful."
A 4-inch-wide shaft is the men's lifeline to the world above.
Spirits have improved, Health Minister Jaime Manalich said, since officials have been able to deliver shirts, rubber shoes and cots to the miners through the narrow tube. The men call it La Paloma, or the pigeon.
Officials also lower daily rations of food through the tube. (On Friday, the men had bread and honey, cauliflower and rice, fortified milk, pork pate and pasta salad.) The miners use a chemical toilet also sent down via the shaft; they've placed it in a tunnel far from their communal "living room" and travel back and forth to the privy in a small gas-powered mining vehicle.
The fact that the miners can now brush their teeth and wash their hair and clothes has "lifted their spirits," psychologist Iturra said.
The men, whose ages range from 19 to 63, have organized themselves into work teams with specific jobs "so they don't think about their disappointment," said Clementina Gomez, aunt of 19-year-old miner Jimmy Sanchez.
One team handles food and water, another cleanup activities and a third mine work, including operating La Paloma.
Their daily routines also include regularly scheduled periods for prayer, exercise — walking around their chamber — and games, including dominoes and dice throwing.
Victor Segovia, 49, has emerged as the miners' chronicler and is keeping a daily account of their activities. His daughter Maritza, interviewed at the tent where she and four siblings keep a vigil, said he is a compulsive writer who leaves lengthy notes every time he leaves the house or goes shopping to explain in detail what he is doing.
"He has also written me a letter every day since they were found. Here is what I've just received from him," Maritza said, waving a crumpled notebook sheet covered on both sides with her father's blocky handwriting.
According to several family members, Mario Gomez, the oldest of the miners, is the spiritual leader and organizes the prayer sessions. His wife, Liliana Ramirez, said perhaps it is her husband's stable personality and deep religious faith that have made him someone the men turn to.
"He's a spiritual man of very few words, but he is friendly to everyone. He has worked in the mines since he was 12 years old," Ramirez said.
When she talked to him, she said, "all he has said is, 'Don't worry about me.' He's more concerned with how the family is doing."
On Saturday, four of the survivors of the 1972 crash of a plane carrying a Uruguayan rugby team appeared at the mine to give encouragement to the miners via a newly installed fiber-optic line.
"We're going to tell them to celebrate that they are alive, that no one was killed in the accident, to enjoy every moment," said Gustavo Servino, one of the survivors, whose story of living more than two months in the snowy Andes was turned into a book and movie. "We have to concentrate on solutions, not problems."
Juan Vergara, a staff psychologist in the Copiapo municipality, said the families have shown considerable resilience in light of the fact that two days after the cave-in, the government said efforts to rescue the miners had failed and withdrew rescue equipment from the site.
"Many assumed it was a lost cause," Vergara said.
But after some family members complained that it was too early to give up, the government drilled several holes, three of which found the refuge and tunnel system where the men are sequestered.
In addition to worrying about the miners' rescue, families are also concerned about their future livelihoods in light of the mining company's declaration of bankruptcy late last month. Will the miners have jobs to go back to?
The government moved last week to allay those fears, promising to find other jobs not just for the 33 trapped miners after their hoped-for rescue but for all 300 San Jose mine workers out of work because of the closure.
On Friday, representatives of the Underground Mine Workers Union appeared at the mine to announce that they were giving each of the trapped miners $13,000. An international fund to support the miners had collected $750,000.
"He seems happy with the little he has," said Campos, the mother, whose son had been working in the mine for six months when the accident happened, attracted by relatively high wages offered by the owners. "He told me in our talk that he was happy that he has quit smoking down there."
But she said that although her son was accentuating the positive, she knew he was afraid and desperate to get out. She vowed not to leave the mine until he is rescued, however long it takes.
"You can't get anything positive from this," she said. "He is suffering down there."
Kraul is a special correspondent.