It's just the crumb of a muffin, but Martha Galvis must pick it up. Lips clenched, eyes narrowed, she pushes it back and forth across a slick table, then in circles.
"I struggle and struggle until," Galvis pauses, concentrating all her attention on the thumb and middle finger of her left hand. She can't get them to close around the crumb.
"I try as much as I can, and if I do it, I'm so happy — so happy," she says, giggling.