You bought the hooded box because it looked like furniture instead of a toilet, and because you did not want to look at what was in it. Three weeks later your cat is peeing on the bath mat beside it, and you are wondering which of you has the problem.
The internet has an answer ready. Cats hate covered boxes, the hood traps the smell, take the lid off. That answer has been repeated for so long that it reads like a finding, and when you go looking for the finding you get two studies, done sixteen years apart, and neither of them produced evidence against the hood.
What the earlier study found
In 1997, Debra Horwitz published a retrospective study of 144 cats in Applied Animal Behaviour Science, looking for environmental factors associated with elimination problems. Box style was one of the variables she examined. She found no significant association between covered boxes and cats eliminating outside the box.
She also recorded how often the boxes were cleaned, and the numbers there were not evenly distributed. Among the cats with elimination problems, those with covered boxes averaged five days between cleanings. The cats without problems were more likely to have their boxes cleaned daily.
A retrospective study cannot separate those two observations, because the household chooses both. What it establishes is that hoods and infrequent cleaning turned up in the same homes, which is a much weaker statement than the one the internet derived from it.
What the trial did
Grigg, Pick and Nibblett published the experiment in 2013 in the Journal of Feline Medicine and Surgery, and the paper is free to read. Its introduction notes that avoiding covered boxes was already a frequent recommendation even though nobody had tested it experimentally.
Twenty-eight cats were enrolled and twenty-seven were analyzed. The twenty-eighth was dropped because its owner did not follow the protocol. To qualify, a cat needed no elimination disorder in the previous twelve months, behavioral problems included, so the sample never contained a cat that was already avoiding its box. In homes with more than one cat, the study cat was housed away from its housemates for the two weeks.
Both boxes were built from identical plastic storage tubs measuring 82.5 by 50.2 by 47.3 centimeters. The covered one kept its lid and had a 27.3 by 31.75 centimeter opening cut into one end, the bottom of that opening sitting 10 centimeters above the floor. The uncovered one had its sides cut down to 15.2 centimeters, with its front entry cut to the same 10 centimeters as the covered box. Because the tubs matched, box size could not account for a difference, which left the cover as the only variable under test.
Both held the same scented, fine-grained clumping litter, about five centimeters deep and topped up as needed. The boxes stood side by side, and the investigators swapped their positions after the first week so that a cat’s favorite corner of the room could not decide the outcome.
Each day the owners scooped both boxes with identical scoops and put the waste into separate labeled bags, and the investigators weighed the bags. The measurement was grams of waste per box, not anyone’s impression of which box the cat seemed to favor.
What came back
Pooled across all the cats, there was no detectable difference in use between the two styles. The paired t-test gave t(376) = 0.44, P = 0.66.
Nineteen of the twenty-seven cats, 70 percent, showed no preference at all. Four used the covered box significantly more and four preferred the uncovered one. The paper reports that more cats than expected showed no preference, testing the 19-4-4 split against the roughly nine-nine-nine you would get if the three outcomes were equally likely, for a chi-square of 16.67. The authors then postulate that when a box is kept clean enough, a daily scoop at minimum, most cats will not show a preference either way.
They also looked for what distinguished the eight cats who did care, testing age, sex, size, the social setting of the household, and whether the cat had used a covered box before. The paper is candid that eight cats split four and four is too small a group to demonstrate a relationship, and that this covariate analysis proved difficult for exactly that reason. Social setting came back at P = 0.157, with no significant relationship.
What the paper does offer beyond that are patterns it labels as needing further research. None of the six cats weighing six kilograms or more preferred the covered box, though two preferred the uncovered one. Cats from multi-cat households appeared somewhat more likely to have a preference. Neither observation reached significance, and the second one is the weaker of the two, because the design could not test the thing most people want to know: whether a cat in a busy multi-cat home avoids a hood.
With twenty-seven cats, the design would likely have caught only a large preference. A modest one shared by half the sample would have passed through unnoticed. So the result is an absence of detectable difference, which is not the same claim as the two styles being equivalent.
The box they tested is not the box in your hallway
The study box is 82.5 centimeters long, about 32 inches, and the uncovered version was a shallow tray with 15.2 centimeter walls. Take a tape measure to whatever is in your hallway before treating any of this as settled.
The authors describe their setup as an “ideal litter box in all respects other than the study variable,” which is a design choice and a limitation at the same time. They built a box that satisfied every recommendation they could find so that the cover would be the only thing left for a cat to object to. A hooded box from a pet store is typically smaller and usually fitted with a flap door, which is a different object from the one the trial used.
The paper flags its own litter as well. What they used was scented, the paper calls the influence of litter fragrance unclear, and one cat in the trial, a Persian, had reportedly avoided the covered box when it held scented litter, preferred the uncovered box during the study, and then went back to the covered one once its owner replaced the scented litter with unscented. The paper’s reading of that is narrower than “the lid was fine”: it suggests the cover may intensify a scented litter, which would make the fragrance aversive in a hooded box specifically. On that account the lid is an amplifier rather than the cause. The authors name unscented litter as a change a replication should make.
Where the trial’s own advice lands
Because the tub was oversized, the authors note that an owner who wants to keep a covered box may need a larger one than the store sells, particularly for a cat of six kilograms or more, and that such a box is easy to build from a plastic storage tub with an opening cut into one end.
That is the size the evidence actually tested, and building one is a hardware-store errand.
Reasons to keep a lid
A dog who digs in the litter box is a good reason for a cover, since it turns the box into something the dog has to work at. A toddler is another, for the same reason, and neither has anything to do with what the cat wants.
Scatter is the other common reason, and a real one. Some cats dig as though burying evidence, and a high-sided covered box keeps the mess inside it. A high-sided open box does the same job if you would rather keep the airflow.
Smell cuts both ways, and the two directions get conflated. One reason people buy a hood is containment: the odor stays near the box instead of reaching the sofa. The reason the paper lists in favor of removing one is the same fact seen from the cat’s side, since it notes that covered boxes “tends to trap waste odors.” Neither study measured how much either effect is worth. What a lid plainly does is slow air exchange around the box, and if your cat has a respiratory condition, that belongs in a conversation with your vet.
Reasons to take it off
The clearest cost of a hood is that you stop seeing the output. Uncovered, you notice that the urine clumps got smaller, that there is blood, that the stool changed shape, that the cat is straining. Covered, those signals sit behind a lid you have no reason to open, and the first sign you get is often a cat who has not produced urine at all, which is an emergency rather than a warning. No study is required to establish that.
Age produces the same conclusion by a different route. A high wall and a step-over are nothing to a young cat and an obstacle to an arthritic one, so when an older cat starts missing the box, the lid comes off before anything else changes.
With several cats, the evidence runs out rather than pointing anywhere, and removing the lid is a cheap experiment to run while you work out what is actually going on.
Testing it on your own cat
Put both boxes side by side and swap their positions after a week, which is what the study did and what controls for the cat’s preference for one corner of the room. Putting them in separate rooms is a more realistic arrangement and a different experiment, and it helps to know which one you are running.
Scoop both daily, since that is the condition the whole finding rests on, and a test where one box is dirtier is measuring hygiene. Give it two weeks, the same period as the trial, because a cautious cat may take several days to try anything new.
Then look at which one is consistently fuller. If both get used evenly, keep whichever suits the room. If one wins, you have your answer for the price of a second box. If the cat refuses both and goes on the bath mat, the lid was never the issue, and the next things to check are the litter, the location, and whether the box is large enough for the cat to turn around in.
What to buy
A covered box with a removable hood is the sensible middle, because you can run the experiment and undo it in a moment. Skip the flap door if you can. That is reasoning rather than evidence, since nothing here tested the flap, but it is one more thing between the cat and the box, and a cat who dislikes it will not explain why.
For either style, buy by measurement. A cat has to be able to turn around inside what you buy, and the trial used something 32 inches long.
The part the lid cannot fix
A covered box does not make a dirty box acceptable. It has been suggested in print that owners scoop less when they cannot see the waste. The Grigg paper reports that suggestion without testing it, and if it holds then the lid solves an aesthetic problem by creating a maintenance problem you cannot see.
Either way, the daily scoop is what carries the result. In the 2013 trial both boxes were cleaned every day, and that is the condition under which most cats turned out not to care. Remove it and you are running a different experiment, on a cat who never agreed to be in one.