Tonight, many parents will start wishing they had a Ph.D., which maybe would help them figure out "some assembly required" toys. From dollhouses to train sets to electronic gadgets, it can be a long night for Santa's helpers, even aided by extra-strength eggnog.

So The Times wondered, "Do rocket scientists (or brain surgeons or mechanical engineers) have an advantage on Christmas Eve? Do kid toys ever stump them?"

We asked some really smart experts. Their answer to both: Sometimes.

Jens Gundlach is a physics professor at the University of Washington's Center for Experimental Nuclear Physics and Astrophysics.

His credentials include building instruments to test general relativity, search for extra dimensions and precisely measure the mass of the Earth. He's part of a NASA project to build a giant gravitational-wave antenna in space to detect signals from colliding black holes.

But even he resorted to cursing and, yes, reading the instructions when trying to put together the Slimecano — a Mattel Hot Wheels play set featuring a goo-oozing volcano — for his then-6-year-old son. In the end, he gave up.

"With the task 30 percent completed, I left for work, where my high-tech physics experiments are far more relaxing," said the father of three boys, ages 7, 4 and 1. He and his wife later managed to activate a roaring sound and shaking motion but left off various latches and tracks. "All the other plastic stuff on it would have required re-engineering," he explained. "Lots of parts didn't fit or function right."

While a career fixing things — human or machine — does make it easier for experts to see how parts relate to each other, they all remembered a Little Toy That Couldn't.

"It's not so much innate ability, just patience," said Dr. Ryder Gwinn, a neurosurgeon with the Seattle Neuroscience Institute at Swedish Medical Center. "You have to like putting things together. I enjoy it so my patience is higher."

He's lucky that Santa Claus (hi, kids!) brings most toys ready to go. But he did spend most of one Christmas morning assembling a dollhouse. "I got to the end and there were still some extra pieces left over," admitted the Bellevue dad of three, ages 8, 6 and 1.

He also attached railings on opposite sides, which he had to take apart and put back on the right way. "I probably should have read the directions."

Greg Mason, a Seattle University engineering professor, also admits a typical male aversion to instructions (despite his own advice, see "Professor Dad says: Read the directions"). He might glance at them, but mostly "I make up my own," said the Bremerton dad of two, ages 9 and 13.

When his son opened a motorized tank that immediately lost a wheel, "as an engineer, I refused to give up on it," he said. "I spent the next three hours basically rebuilding the toy. It was way over-engineered by the time the toy was put together. That wheel was never going to fall off again."

For him, it's a personal challenge. "It's a puzzle," he said. "Who cares about the toy?"

Teodora Rutar Shuman, also a mechanical engineering professor at Seattle University, generally finds toy instructions helpful. "I've never had a problem when I followed the directions," said the Kirkland mom of two girls, ages 3 ½ and almost 2.

Except once. Shuman helped her sister assemble a large toy for her nephew that featured balls rolling down ramps to spin gears and wheels. "Maybe you can figure this out," her sister told her when she called for assistance.

But even with Shuman's engineering expertise, "that darn thing just would not stay together," she said. "You'd walk by it, the floor would squeak and it would fall over."

Sometimes parents just have to concede they got duped into buying a difficult toy.

Gundlach calls his dalliance with the Slimecano "a pretty frustrating experience" that wasn't helped by the length of his son's infatuation: a day. Along with the toy's age-5-and-up recommendation, he suggests the manufacturer include a minimum age for assembly. "Ages 40-plus have a problem with it, OK?"

Or maybe the younger age really is right. Two years ago, Mason was perplexed by a 30-piece pony castle for his then-7-year-old daughter. It fit together except "one crazy piece." "Two weeks later, my daughter walked up and snapped it right in."

Stephanie Dunnewind: sdunnewind@seattletimes.com or 206-464-2091.