Chewable things: Good.

Squeaky things: Eh, could take ’em or leave ’em.

Hard plastic things that are virtually indestructible: Well, what is that point of that?

Those were the verdicts of shelter dogs in Northern Ireland who played with a series of toys for five weeks under the watchful eye of psychologist and animal behavior expert Deborah Wells. Published in the British journal Animal Welfare (Vol. 13, 2004), Wells’s latest study reveals that while chewable plastic reigns supreme among kenneled dogs in shelters, no toy seems to hold their attention for long.

As the director of the Canine Behaviour Centre at Queen’s University Belfast, Wells has spent hundreds of hours observing dogs in the shelter environment and measuring how they react to classical music, toys, cage locations, and the presence of visitors. In her most recent research, “The influence of toys on the behaviour and welfare of kenneled dogs,” she gave each of 32 guests of the Dogs Trust Rehoming Centre in Ballymena one toy a week over a five-week period: a chewable plastic squeaky ball, a chewable plastic nonsqueaky ball, a cotton tug rope, a flexible plastic Nylabone chew, and a “virtually indestructible impact-resistant pursuit toy” called a Boomer ball.

After observing the behavior of each dog every 10 minutes for four hours on days 1, 3, and 5 of each week, Wells discovered a strong poochy preference for the Nylabone over any other toy tested and an almost complete indifference to the Boomer ball. And the squeakiest ball of them all failed to get the grease; its noisemaking abilities didn’t give it much of an edge over the nonsqueaky ball, leading Wells to suggest that “the type of noise a toy emits may be of less value to dogs than the fact that the toy can be chewed.”

Overall, dogs grew less interested in the toys as the days passed. Frequency of playtime was highest on the first day of a new toy’s introduction and waned considerably by day 5.

“The introduction of a novel toy, however, generated renewed interest,” wrote Wells. “Rotating toys, so that dogs are regularly exposed to novel stimuli, may be one means of reducing habituation to toys and of encouraging exploration in rescue shelter dogs.”

The dogs in the study were less interested in toys overall than dogs in laboratory settings, confirming the findings of previous research. The older age of shelter dogs could be a factor in varying interest levels, Wells posited, as could the environment itself. Shelters are highly stimulating places for animals, and the noise combined with the presence of staff and visitors might overpower the attraction of a solitary, inanimate object.

Still, toys led to increased activity and engaged the dogs in the study for at least a little while, so their long-term effects, however indirect, can’t be overlooked, Wells wrote. Previous studies by Wells and her colleagues had found that potential adopters preferred dogs with enrichment items in their kennels—and that the presence of toys in kennels greatly increased dogs’ chances of being adopted. Visitors were also attracted to dogs who displayed active behaviors—something the toys in the latest study encouraged.

Results of such a study in the United States may be slightly different for two reasons. First, Kongs or Kong-like toys were not a part of the new toy study; Wells wanted to avoid food-filled items that would be inappropriate for kennels shared by more than one dog. And second, the dogs in the study had been living at the site for six to eight months and may have exhibited reactions different from those of short-term guests in most U.S. shelters.

Still, some things are universal, and the conclusion that dogs like chewing more than noisemaking in the shelter may be applicable in any setting. Rotation of toys may also help sustain their interest, decrease boredom, and provide canine guests with a more comfortable stay in their temporary homes.