Science
James Reason, Who Used Swiss Cheese to Explain Human Error, Dies at 86
The story of how James Reason became an authority on the psychology of human error begins with a teapot.
It was the early 1970s. He was a professor at the University of Leicester, in England, studying motion sickness, a process that involved spinning his subjects round and round, and occasionally revealing what they had eaten for breakfast.
One afternoon, as he was boiling water in his kitchen to make tea, his cat, a brown Burmese named Rusky, sauntered in meowing for food. “I opened a tin of cat food,” he later recalled, “dug in a spoon and dolloped a large spoonful of cat food into the teapot.”
After swearing at Rusky, Professor Reason berated himself: How could he have done something so stupid?
The question seemed more intellectually engaging than making people dizzy, so he ditched motion sickness to study why humans make mistakes, particularly in high-risk settings.
By analyzing hundreds of accidents in aviation, railway travel, medicine and nuclear power, Professor Reason concluded that human errors were usually the byproduct of circumstances — in his case, the cat food was stored near the tea leaves, and the cat had walked in just as he was boiling water — rather than being caused by careless or malicious behavior.
That was how he arrived at his Swiss cheese model of failure, a metaphor for analyzing and preventing accidents that envisions situations in which multiple vulnerabilities in safety measures — the holes in the cheese — align to create a recipe for tragedy.
“Some scholars play a critical role in founding a whole field of study: Sigmund Freud, in psychology. Noam Chomsky, in linguistics. Albert Einstein, in modern physics,” Robert L. Sumwalt, the former chairman of National Transportation Safety Board, wrote in a 2018 blog post. “In the field of safety, Dr. James Reason has played such a role.”
Professor Reason died on Feb. 4 in Slough, a town about 20 miles west of London. He was 86.
His death, in a hospital, was caused by pneumonia, his family said.
A gifted storyteller, Professor Reason found vivid and witty ways to explain complicated ideas. At conferences, on TV news programs and in consultation with government safety officials around the world, he would sometimes deploy slices of cheese as props.
In one instructional video, he sat at his dining room table, which was set for a romantic dinner, with a bottle of wine, two glasses and a cutting board layered with cheese.
“In an ideal world, each defense would look like this,” he said, holding up a slice of cheese without holes. “It would be solid and intact.”
Then he reached for another slice, one with quarter-size cutouts. “But in reality, each defense is like this,” he said. “It has holes in it.”
The metaphor was easy to understand.
“All defenses have holes in them,” Professor Reason continued. “Every now and again, the holes line up so that there can be some trajectory of accident opportunity.”
To explain how the holes develop, he put them in two categories: active failures, or mistakes typically made by people who, for example, grab the cat food instead of the tea leaves; and latent conditions, or mistakes made in construction, written instructions or system design, like storing two scoopable substances near each other in a cabinet.
“Nearly all organizational accidents involve a complex interaction between these two sets of factors,” he wrote in his autobiography, “A Life in Error: From Little Slips to Big Disasters” (2013).
In the Chernobyl nuclear accident, he identified latent conditions that had been in existence for years: a poorly designed reactor; organizational mismanagement; and inadequate training procedures and supervision for frontline operators, who triggered the catastrophic explosion by making the error of turning off several safety systems at once.
“Rather than being the main instigators of an accident, operators tend to be the inheritors of system defects,” he wrote in “Human Error” (1990). “Their part is that of adding the final garnish to a lethal brew whose ingredients have already been long in the cooking.”
Professor Reason’s model has been widely used in health care.
“When I was in medical school, an error meant you screwed up, and you should just try harder to not screw up,” Robert Wachter, the chairman of the department of medicine at the University of California San Francisco, said in an interview. “And if it was really bad, you would probably get sued.”
In 1998, a doctor he had recently hired for a fellowship said he wanted to specialize in patient-safety strategy, to which Dr. Wachter replied, “What’s that?” There were no formal systems or methods in his hospital (or most others) to analyze and prevent errors, but there was plenty of blame to go around, most of it aimed at doctors and nurses.
This particular doctor had trained at Harvard Medical School, where they were incorporating Professor Reason’s ideas into patient-safety programs. Dr. Wachter, who began reading Professor Reason’s journal articles and books, said the Swiss cheese model was “an epiphany,” almost “like putting on a new pair of glasses.”
Someone given the wrong dose of medicine, he realized, could have been the victim of poor syringe design rather than a careless nurse. Another patient could have died of cardiac arrest because a defibrillator that was usually stored in the hallway had been taken to a different floor to replace one that had malfunctioned — and there was no system to alert anyone that it had been moved.
“When an error happens, our instinct can’t be to look at this at the final stage,” Dr. Wachter said, “but to look at the entirety of the system.”
When you do, he added, you realize that “these layers of protection are pretty porous in ways that you just didn’t understand until we opened our eyes to all of it.”
James Tootle was born on May 1, 1938, in Garston, a village in Hertfordshire, northwest of London. His father, Stanley Tootle, died in 1940, during World War II, when he was struck by shrapnel while playing cards in the bay window of his house. His mother, Hilda (Reason) Tootle, died when he was a teenager.
His grandfather, Thomas Augustus Reason, raised James, who took his surname.
In 1962, he graduated from the University of Manchester with a degree in psychology. He received his doctorate in 1967 from the University of Leicester, where he taught and conducted research before joining the faculty at the University of Manchester in 1977.
He married Rea Jaari, an educational psychologist, in 1964. She survives him, along with their daughters, Paula Reason and Helen Moss, and three grandchildren.
Throughout his career, Professor Reason’s surname was a reliable source of levity.
“The word ‘reason’ is, of course, widely used in the English language, but it does not describe what Jim is rightly famous for, namely ‘error,’” Erik Hollnagel, the founding editor of the International Journal of Cognition, Technology and Work, wrote in the preface to Professor Reason’s autobiography. “Indeed, ‘error’ is almost the opposite of ‘reason.’”
Still, it made sense.
“Jim has certainly brought reason to the study of error,” he wrote.
WASHINGTON — NASA recaptured the world’s attention with Artemis II, which took astronauts to the moon and back for the first time in half a century. But the agency’s scientific projects could again be under threat as the Trump administration makes a renewed push to drastically cut their funding — including at the Jet Propulsion Laboratory.
The cuts, proposed in the Trump administration’s 2027 budget request to Congress, would pose further challenges to the already weakened Caltech-managed lab and could be broadly damaging to American efforts to bring back new discoveries from space. They echo last year’s attempt by the administration to slash NASA funding, which Congress rejected.
Though the Artemis project is billed as laying a foundation for a crewed NASA mission to Mars, exploration of the Red Planet is among the endeavors that could be slashed. The rover currently exploring Mars’ ancient river delta and a mission to orbit Venus are among projects with JPL involvement targeted for spending cuts, according to an analysis of the NASA budget proposal by the nonprofit Planetary Society.
“This isn’t [because] they’re not producing good science anymore. There’s no rhyme or reason to it,” said Casey Dreier, chief of space policy at the Planetary Society, which led opposition to the administration’s similar effort to cut NASA funding last year.
Storm clouds hang over the Jet Propulsion Laboratory on Feb. 7, 2024.
(David McNew / Getty Images)
This time, the administration is asking Congress to cut NASA funding by 23% — including a 46% cut to its science programs, which are responsible for developing spacecraft, sending them into outer space to observe and analyzing the data they send back.
The proposal would cancel 53 science missions and reduce funding for others, according to the Planetary Society analysis. The effort to pare down NASA Science comes amid the Trump administration’s broader effort to cut scientific research across federal agencies.
The plan swiftly drew bipartisan criticism from members of Congress, who rejected the administration’s similar 2026 proposal in January. Republican Sen. Jerry Moran of Kansas, who chairs the Senate appropriations subcommittee that oversees NASA, indicated last week that he would work to fund NASA similarly for 2027, saying it would be “a mistake” not to fund science missions.
Moran plans to hold a hearing with NASA Administrator Jared Isaacman before the end of April to review the budget request, a spokesperson for his office said. The president’s budget request is an ask to Congress, which ultimately holds the power to allocate funding.
But until Congress creates its own budget, NASA will use the plan as its road map, which could slow grants and contracts. The proposal “still creates enormous chaos and uncertainty in the meantime for critical missions, the scientific workforce, and long-term research planning,” said Rep. Judy Chu (D-Monterey Park), whose district includes JPL.
A NASA spokesperson declined to comment Friday. In the budget request, Isaacman wrote that NASA was “pursuing a focused and right-sized portfolio” for its space science missions in order to align with Trump’s federal cost-cutting goals.
The budget “reinforces U.S. leadership in space science through groundbreaking missions, completed research, and next-generation observatories,” Isaacman wrote.
Jared Isaacman testifies during his confirmation hearing to be the NASA administrator in the Russell Senate Office Building on Capitol Hill on Dec. 3, 2025.
(Anna Moneymaker / Getty Images)
At JPL — which has for decades led innovation in space science and technology from its La Cañada Flintridge campus — questions had already swirled about the lab’s role in the future of NASA work.
Multiple rounds of layoffs over the last two years, the defunding of its embattled Mars Sample Return mission and a shift by the Trump administration toward lunar exploration and away from the type of scientific work that JPL executes had pushed the lab into a challenging stretch.
It has had a steady stream of employee departures in recent months, and those left have been scrambling to court outside funding from private investors, sell JPL technology to companies and increase productivity in hopes of keeping the lab afloat, according to two former staffers, who requested anonymity to describe the mood inside the lab.
“If we’re not doing science, then what are we doing?” asked one former employee, who recently left JPL after more than a decade there.
A spokesperson for the lab declined to comment, referring The Times to the budget proposal.
The NASA programs marked for cancellation or cutbacks support thousands of jobs at JPL and other centers, said Chu, who has led a push for increased funding for NASA Science. After last year’s layoffs, JPL “cannot afford to lose more of this expertise,” she said in a statement.
Among the JPL projects that appear to be slated for cancellation are two involving Venus, Dreier said. One, Veritas, is early in development and would give work to the lab for the next several years, he said.
The project would be the first U.S. mission to Venus in more than 30 years, Dreier said, and aims to make a high-resolution mapping of the planet’s surface and observe its atmosphere.
The Perseverance rover, which is on Mars collecting rock and soil samples, could face spending reductions. The budget request proposes pulling some funding from Perseverance to fund other planetary science missions and reducing “the pace of operations” for the rover.
Though how the Mars samples might get back to Earth is uncertain, the rover is still being used to explore the planet and search for evidence of whether it could have ever been habitable to life.
Researchers hope the tubes of Martian rock, soil and sediment can eventually be brought back to Earth for study. The team has about a half a dozen more sample tubes to fill and the rover is in good shape, said Jim Bell, a planetary scientist and Arizona State University professor who leads the camera team on Perseverance, which works daily with JPL.
He said NASA’s spending proposal put forth “no plan” for the future of the agency’s work.
“Are people just supposed to walk away from their consoles,” Bell asked, “and let these orbiters around other planets or rovers on other worlds — just let them die?”
The NASA document did not clearly show which programs were targeted for cuts and did not list which projects were targeted for cancellation. The Planetary Society and the American Astronomical Society each analyzed the proposal and found that dozens of projects appeared to be canceled without being named in the document.
Across NASA, other projects slated for cancellation according to the Planetary Society’s analysis include New Horizons, a spacecraft exploring the outer edge of the solar system; the Atmosphere Observing System, a planned project to collect weather, air quality and climate data; and Juno, a spacecraft studying Jupiter.
The administration’s plan also doesn’t prioritize new scientific projects, Bell said, which further jeopardizes long-term job stability and space discovery at centers like JPL.
“We’re going through this long stretch now with very few opportunities to build these spacecrafts,” Bell said. “All of the NASA centers are suffering from the lack of opportunities.”
Last year, the Trump administration proposed to slash NASA’s 2026 funding by nearly half. Instead, Congress approved funding in January that provided $24.4 billion for the agency — a cut of about 29% rather than the proposed 46%. The 2027 budget request asks for $18.8 billion.
Congress kept funding for science missions nearly steady, allocating $7.25 billion for science missions, about a 1% decrease from 2025. The administration had proposed cutting the science investment down to $3.91 billion. This time, the budget requests $3.89 billion.
Under the Trump administration, NASA has put an emphasis on moon exploration, including this month’s successful Artemis II mission. Isaacman, who defended the proposed cuts on CNN last week, touted the agency’s lunar plans, including a project to build a base on the moon.
The agency has indicated commitment to some existing science missions, including the James Webb Space Telescope, the to-be-launched Nancy Grace Roman Space Telescope, the Dragonfly spacecraft set to launch for Saturn’s moon in 2028, and other projects.
“NASA doesn’t have a topline problem, we just need to focus on executing and delivering world-changing outcomes,” Isaacman said on CNN.
Scientists have urged the government not to choose between funding science and exploration but to keep up investment in both.
“It’s ultimately kind of confusing, especially on the heels of the Artemis II mission,” said Roohi Dalal, deputy director for public policy at the American Astronomical Society. “The scientific community … is providing critical services to ensure that the astronauts are able to carry out their mission safely, and yet at the same time, they’re facing this significant cut.”
After years of heated debates among fire officials, scientists and local advocates, California’s Board of Forestry and Fire Protection released new proposed landscaping rules for fire-prone areas Friday that outline what residents can and can’t do within the first 5 feet of their homes.
Many of these proposed rules — designed to reduce the risk of a home burning down amid a wildfire — have wide support (or at least acceptance); however, the most contentious by far has been whether the state would allow healthy plants in the zone.
Many fire officials and safety advocates have essentially argued anything that can burn, will burn and have supported removing virtually anything capable of combustion from this zone within 5 feet of houses, dubbed “Zone Zero.” They point to the string of devastating urban wildfires in recent years as reason to move quickly.
Yet, researchers who study the array of benefits shade and extra foliage can bring to neighborhoods — and local advocates who are worried about the money and labor needed to comply with the regulations — have argued that this approach goes beyond what current science shows is effective. They have, instead, generally been in favor of allowing green, healthy plants within the zone.
The new draft regulations attempt to bridge the gap. They outline more stringent requirements to remove all plants in a new “Safety Zone” within a foot of the house and within a bigger buffer around potential vulnerabilities in a home’s wildfire armor, including windows that can shatter in extreme heat and wooden decks that can easily burst into flames. Everywhere else, the rules would allow residents to maintain some plants, although still with significant restrictions.
The rules generally do not require the removal of healthy trees — instead, they require giving these trees routine haircuts.
Once the state adopts a final version of the rules, homeowners would have three years to get their landscaping in order and up to five years for the bigger asks, including removing all vegetation from the Safety Zone and updating combustible fencing and sheds within 5 feet of the home. New constructions would have to comply immediately.
The rules only apply to areas with notable fire hazard, including urban areas that Cal Fire has determined have “very high” fire hazard and rural wildlands.
Officials with the Board will meet in Calabasas on Thursday from 1 p.m. to 7 p.m. to discuss the new proposal and hear from residents.
-
Share via
Some L.A. residents are championing a proposed fire-safety rule, referred to as “Zone Zero,” requiring the clearance of flammable material within the first five feet of homes. Others are skeptical of its value.
Where is the Safety Zone?
The proposed Safety Zone with stricter requirements to remove all vegetation would extend 1 foot from the exterior walls of a house.
In a few areas with heightened vulnerabilities to wildfires, it extends further.
The Safety Zone covers any land under the overhang of roofs. If the overhang extends 3 feet, so does the Safety Zone in that area. It also extends 2 feet out from any windows, doors and vents, as well as 5 feet out from attached decks.
What plants would be allowed in the Safety Zone?
Generally, nothing that can burn can sit in the Safety Zone. This includes mulch, green grass, bushes and flowers.
What plants would be allowed in the rest of Zone Zero?
Homeowners can keep grasses (and other ground-covers, like moss) in this area, as long as it’s trimmed down to no taller than 3 inches.
The rules also allow small plants — from begonias to succulents — up to 18 inches tall as long as they are spaced out in groups. Residents can also keep spaced-out potted plants under this height, as long as they’re easily movable.
What about fences, trees and gates?
Any sheds or other outbuildings would need noncombustible exterior walls and roofs in Zone Zero — Safety Zone or not.
Residents would have to replace the first five feet of any combustible fencing or gates attached to their house with something made out of a noncombustible material, such as metal.
Trees generally would be allowed in Zone Zero. Homeowners would need to keep any branches one foot away from the walls, five feet above the roof and 10 feet from chimneys.
Residents would also have to remove any branches from the lower third of the tree (or up to 6 feet, whichever is shorter) to prevent fires on the ground from climbing into the canopy.
Some trees with trunks directly up against a house in this 1-foot buffer or under the roof’s overhang might need to go — since keeping branches away from the home could prove difficult (or impossible).
However, the board stressed it wants to avoid the removal of trees whenever feasible and encouraged homeowners to work with their local fire department’s inspectors to find case-by-case solutions.
What’s new and what’s not
Some of the rules discussed in Zone Zero are not new — they’ve been on the books for years, classified as requirements for Zone One, extending 30 feet from the home with generally less strict rules, and Zone Two, extending 100 feet from the house with the least strict rules.
For example, homeowners are already required to remove any dead or dying grasses, plants and trees. They also have to remove leaves, twigs and needles from gutters, and they already cannot keep exposed firewood in piles next to their house.
Residents are also already required to keep grasses shorter than 4 inches; Zone Zero lowers this by an inch.
new video loaded: Rescuers Mount a Likely Final Push to Save a Stranded Whale
By Jorge Mitssunaga
April 17, 2026
-
Culture6 minutes agoFamous Authors’ Less Famous Books
-
Lifestyle12 minutes agoSunday Puzzle: For Mimi
-
Technology24 minutes agoThe future of local TV news has taken a Trumpian turn
-
World30 minutes agoPope Leo says remarks about world being ‘ravaged by a handful of tyrants’ were not aimed at Trump: report
-
Politics36 minutes agoTrump renews bridge, power plant threat against Iran in push for deal, mocks ‘tough guy’ IRGC
-
Health42 minutes agoLoneliness may be silently eroding your memory, new research reveals
-
Sports48 minutes agoESPN’s Stephen A Smith hears boos from WrestleMania 42 crowd
-
Technology54 minutes agoChinese robot breaks human world record in Beijing half-marathon