Friday, June 25, 2010

Cats, Dogs, Strings, and Causality

During a recent cat-related Web search I came across a whole slew of articles that all had similar titles and content, and seemed to be referencing the same study, i..e., the following:

- Cats outsmarted in psychologist's test (Guardian)

- Dogs are smarter than cats, research shows (Telegraph)

- Study claims cats have limited intelligence (San Francisco Examiner)

- Study Finds Dogs Are Smarter Than Cats (KTLA Los Angeles)

The above articles all refer to the study: Domestic cats (Felis catus) do not show causal understanding in a string-pulling task, published in the journal Animal Cognition, September 20091.

In those articles above wherein a comparison is drawn between cats and dogs, an earlier study is also relevant: Dogs ( Canis lupus familiaris) fail to show understanding of means-end connections in a string-pulling task, also published in Animal Cognition, January, 20052.

Now, as someone with an admitted fondness for cats, and who currently resides in a household including no less than four felines, I must of course acknowledge the possibility of a bias in my reading of the articles.

Nonetheless, the main point of my analysis here is not to "defend" cats. I have no fear of data and I am certainly prepared to accept whatever a well-designed experiment might demonstrate. I also welcome any feedback indicating whether I've somehow managed to misinterpret or misconstrue the results.

Moreover, as I don't have the university connections or what-have-you to access scientific journals for free, I decided to only pay for and read in full the cat study. I have only read the abstract of the dog study. Given these disclosures, take this writing for whatever it is worth.

But anyway. On to the analysis itself.

In each case, the target animals (either cats or dogs) were presented with three tasks in which a food treat was attached to a length of string.

The baited string was then placed in a low-sided box under a clear plastic screen, either alone or in conjunction with a "dummy" (unbaited) string. Three scenarios were presented: one in which a single string with a treat at the end was employed, one in which two strings (one baited and one not) were placed parallel to one another, and a third in which the two strings were angled and/or crossed.

In all scenarios, the ends of the string jutted out far enough for the animals to reach, but the animals could not (due to the dimensions of the setup) directly access the treat itself; in short, they needed to pull on the string in order to get the food.

The results? Per the dog study abstract:

...the dogs were successful if the treat was in a perpendicular line to the barrier, i.e. straight ahead, but not when the string was at an angle: in the latter condition, the typical response was a proximity error in that the dogs pawed or mouthed at a location closest in line to the treat. When two strings that crossed were present, the dogs tended to pull on the wrong string.2

...and per the cat study abstract:

All cats succeeded at pulling a single string to obtain a treat, but none consistently chose the correct string when two strings were parallel. When tested with two crossed strings one cat chose the wrong string consistently and all others performed at chance level.1

Next, let us examine the conclusion suggested by the researchers as a valid interpretation of each study:

Regarding dogs, it was stated that "The combined results from the experiments show that, although dogs can learn to pull on a string to obtain food, they do not spontaneously understand means-end connections involving strings."2

Regarding cats, it was stated that "There was no evidence that cats understand the function of the strings or their physical causality."1

When I read the conclusion of the cat study (in the abstract), that was basically the point at which I determined I needed to read the full text of the study. This certainly revealed quite a bit more information about the experiment, its premise, and its (per the authors) implications than the abstract, and gave quite a different picture of the situation than the popular articles.

If I hadn't been convinced previously that it is both useful to read actual papers and question popular media interpretations of said papers, I certainly am now.

For the paper does not actually say anywhere in it that "dogs are smarter than cats" or that "cats are not actually all that clever". And it would not be correct to interpret the study's conclusion as being that cats do not comprehend the behavior of physical objects at all, considering that the tasks this study entailed were all highly specific string-pulling tasks.

Rather, what the study (or rather studies) point out is that per particular models of developmental cognition, cats' performance on the string tasks indicates one level of causality understanding, whereas dogs' performance indicates a slightly different level. The study isn't perfectly written and it seemed like there were some inferential gaps between data and conclusion, however, the media articles referencing this study seem to me to be vastly over-generalizing this to imply something about dog and cat cognition overall.

Moreover, in the cat paper at least, it is acknowledged that performance differences could be due to the canine and feline species' different types of optimization, i.e., cats as solitary hunters of small prey that tends to dart in and out of sight evolved to exhibit higher-level object permanence abilities. Whereas dogs as pack hunters, due to the need to both track large prey and coordinate efforts with other dogs, may have developed a better grasp of specific types of physical-object relationships than cats.

All that said, I am finding myself rather perplexed by the paper's conclusion that the cats do not understand the function of the string. I have seen my cats yank on string, and on the tails of toy mice, etc., on many occasions when these items are stuck under another object (like the couch). So unless I am misconstruing what it means to "understand" something, I have difficulty seeing how a statement that cats do not understand what string does could possibly be valid (again, I welcome corrections if in fact I am wrong on my interpretations here).

I was also unable to find (in reference to the dog paper) a ready definition of "means-ends connection". But at any rate, the studies seemed to be suggesting that if an animal truly comprehends the physical properties of the string attached to the treat, s/he will take advantage of those properties in order to obtain the treat.

Hence if the animal in a given trial either (a) fails entirely to obtain the treat even after considerable effort, or (b) obtains the treat inconsistently and/or inefficiently, it is often concluded that the animal simply does not understand that grasping, pulling, or otherwise manipulating the string in a particular way will guarantee or hasten access to the treat.

But all that said, I am not convinced that the experimental setup (in the cat study at least, as that is the one I actually read the paper describing) would have been adequate to test cats' understanding of the function of the string. For one thing, it was not clear to me in either reading the experimental equipment description or viewing a photograph of said equipment how the cats were expected to detect the presence of a treat (attached to a given piece of string) in the first place.

The paper noted several animals that had been successful in many string tasks that supposedly demonstrated causal understanding in excess of cats (or dogs, for that matter). And while I do not doubt of course that different species can and do indeed exhibit different sorts of cognitive optimization, it does strike me as interesting that all the string-test-passing animals mentioned (primates and corvids, for instance) have relatively high visual acuity compared to cats.

Felines, being crepuscular hunters of small prey, have evolved visual systems optimized for detecting tiny, subtle movements in low light conditions.4 Cats hence see vastly better than humans and somewhat better than dogs in relative darkness, and are highly adept at detecting even the smallest hint of motion in their peripheral vision.

Nevertheless, felines cannot distinguish as many colors as, say, primates or birds (most mammals, including both cats and dogs are actually dichromatic). Moreover, their visual acuity for fine details is relatively poor, especially at close range. Dogs also have fairly poor visual acuity as compared to humans, however, theirs is still estimated to be about twice that of cats. 3

This raises the question of whether the cats in the string-pulling study failed to pull the "correct" string in part simply because they could not see where the treat was attached. From the photos I found of the setup it looked as if the treat was fairly physically small (not much larger than the end of the piece of string) and that the cats were expected to perform the task when positioned quite close to the setup.

Additionally, the presence of the plastic screen, while certainly vital to the setup in terms of blocking direct access to the treats, would not have allowed the cats to identify the location of the treat by smell.** Nor could the cats touch the treat or string under the screen with their paws, or brush against it with their whiskers. I have watched my cats chase after small treats I toss across the room, and what I have noticed is that their eyes "lock on" to the treat while it is in motion flying through the air, and then when it lands, they will sniff around on the floor near the end of its trajectory until they find it. In other words, they do not seem to be using their eyes to find the treat at close range, but their noses.

Add to that the fact that the treat was, from all appearances, just sitting there motionless at the end of the string, and you've essentially removed all the major perceptual modalities that could actually assure the cat of the treat's location. Unless there was some provision made not described in the paper to account for this, I would be inclined to figure that a "random guess" strategy would in fact be the most logical one available to the cats tested.

After all, as opportunistic predators, cats are not so much inclined toward "efficiency" but rather toward trying something that seems like it might have the potential to lead to something tasty or otherwise interesting. Which could certainly contribute toward a decision to pull on both strings, or on a random one, etc.

** CORRECTION (7/16/2010): Following a closer reading of the study's apparatus description, I realized that the referenced cat study had not employed a solid transparent plastic lid with gridlines drawn on it (as I had presumed from the setup photo) but rather a wire mesh screen. Hence, my original statement that the study apparatus would not have allowed the cats to smell the treats was in error. This, however, does not negate my other observations, and moreover, given the apparent height of the box used in the study (see photo again) it is unclear to me whether the cats would have been able to precisely pinpoint the location of the treats by smell.


Primary Reference:

1-Whitt, E., Douglas, M., Osthaus, B., & Hocking, I. (2009). Domestic cats (Felis catus) do not show causal understanding in a string-pulling task Animal Cognition, 12 (5), 739-743 DOI: 10.1007/s10071-009-0228-x

Secondary References:
2- Britta Osthaus, Stephen E. G. Lea1 and Alan M. Slater (2005).
Dogs ( Canis lupus familiaris) fail to show understanding of means-end connections in a string-pulling task
Animal Cognition, Volume 9, Number 1 / January, 2005

3- From

Visual acuity is the ability to see the details of an object separately and unblurred. Acuity is measured in "cycles per degree", which means how many lines you can distinguish as being separate in a degree of the visual field. Humans see 30 cycles per degree, horses 18, dogs 12 and cats 6. Acuity in dogs is 0.4 times that of people, 0.67 times that of horses, and twice that of cats. Acuity in cats is 0.2 times that of people, 0.33 times that of horses, and 0.5 times that of dogs. If normal human vision is 20/20, then that of the dog between 20/50 to 20/100, the horse 20/33, and that of the cat is 20/100.

4- Fundamentals of veterinary opthamology, Douglas H. Slatter, p8


Cosma Shalizi said...

I have access to the dog study through my university's subscription. Please write if you'd like a copy.

Mini-me said...

"The best thinking has been done in solitude."
-Thomas A. Edison

This is a classic case of apples & oranges, as I see it. Animal psychology is indeed an interesting topic. I might have missed it, how closely do small dogs test with cats?

Anne Corwin said...

Mini-me: I don't think the dog study had anything to do with what size the dogs were; I do have a copy of it now (thanks to Cosma Shalizi!) so I can confirm that at some point, though.

But as I understand it the dogs in the dog study were able to fairly consistently pass the "parallel strings" task, but not the "crossed strings" task (or one in which the strings were placed at a 90 degree angle). Cats in the cat study only consistently passed the single-string test. But as I noted in my post there are many reasons other than cats not understanding the function of string that could have led to this result, and I don't think the study necessarily accounted sufficiently for those reasons.

Incidentally, I ran a similar test on my cats and have some videos showing the results of that -- 2 of the 4 felines here were not interested in trying the task, but the two that were interested seemed pretty good at both the parallel AND the crossed string cases so long as the treats at the end of the string were highly visible (I used a larger "treat receptacle" and made sure that the food contrasted strongly with the background so the kitties would be better able to see it). They all either ignored the setup or pawed randomly at it when I just had, say, a single piece of food tied to the end of a string.

Mini-me said...

Cool. Maybe they picked up on your attention to detail and focus on something in particular, and it was less about the nugget of goodness from above? Maybe they are workaholics? And also, maybe they are comedians? :]

Justthisguy said...

My kitty is pretty smart, though he seems a slow thinker. I mean, he's pretty quick at ordinary cat skills like killin', and all, but when dealing with human things he seems to take a while to process the program, so to speak. Small processor, slow clock speed, but eventually does figure out the problem. Reminds me of way back when, in the seventies, when people tried to write efficient code for small machines with not much memory.

Oh, BTW, your list of tools on the window-seat post inspired me to emit a blog post about a pair of Vise-Grip pliers. I really do think I feel a bit of a perseveration coming on. Please check out the post and tell me what you think about it there. Feel free to speak your mind.

Anne Corwin said...

Justthisguy: Interesting re. your cat's skill set. With my kitties it seems like they all sort of have different areas of high interest/motivation/ability, though of course there is some overlap seeing as they're all cats!

Coraline and Brodie are more "mechanically inclined", for instance, whereas Shadow and Nikki are more "socially inclined" -- i.e., Cora and Brodie would just as soon get a treat themselves if they can figure out how, whereas Shadow and Nikki would both rather demand that YOU give them the treat. That's a vast generalization of course and there are exceptions, but those are the trends I see.

Oh and I will definitely check out your tools post(s), for sure. I have another project post coming up as I am refinishing a night-stand I got at Goodwill but I am not sure when I will get around to actually writing the post.

Justthisguy said...

Thanks for responding, Ma'am! I just rubbed the Vise-Grips again. Really, I like the new finish, it feels good when I rub it.

Anne Corwin said...

JTG: I think I know the kind of finish you mean...the metal on some tools that's sort of rough and sparkly? I love that stuff. It also smells good but that could be the oil or something they use. I like metallic and "garage" smells, though.

Anonymous said...


Firstly, journalism loves to sucker readers into a dead-end argument. There are classes advertizers take about how to make data/polls/research say what you want them to say.

Next, cats are awesome.

Smartness and intellegence gets called dumbness. Is it really smarter to assign the closer string as the treat-getter? That simple assumption can profit many good results, but the reptilian assumpition and action are not the mamallian-super-brain style that humans and dolphins like to praise.

An awareness of potential complexity can manifest oddly to shallow appearances.

As for the experiment itself, it's narrow, and presumptive from the start. I'm curious as to how humans respond to the same tests, particularly since it is a human concept of intelligence that is being referenced.

At any rate, my appreciation for animals is probably more eternally pertinent than any analysis, since it's coming from an un-denied fact ... I like them. That's a decent scientific fact.

Thanks for the blogging, keep up the cool meandering interests 8)

Anonymous said...


"cognitive optimization"

great line

Justthisguy said...

I don't think any metal object has a particular smell, unles you have just scraped it with a file, or something. I need to find my bottle of Break-Free and use it to lubricate the screw on the Vise-Grip pliers. I feel some kind of gritty sensation when turning that screw.

Really, I must stop stimming on this tool, but I can't help myself.


Justthisguy said...

Oh, on smells: I have heard that smell memories stick in one's head more than any other kind. Every time I walk behind a restaurant and smell a heated-oil smell, I think of running model-airplane engines, back in the fifties and sixties. Glow fuel is about 60% methanol, and 30% castor oil, with the balance made up of nitromethane.

Somehow, the exhaust fans behind Chinese restaurants remind me of running model-airplane engines. They seem to smell very much alike.

I believe that LeRoy Cox made a whole bunch of model-airplane engines in your part of the country.

Oh, there is nothing else like the sensation one gets from flipping a nice sharp nylon propeller on a model-airplane engine with a juicy prime, in cold weather, and have it kick back and slice yer finger. The methanol makes it hurt more, trust me. Sadly, all the scars from my youthful propeller-cuts seem to have faded away, so I have no evidence for what I say except for what I say.

Anonymous said...

You've got to try this one. Gather all your kitties and watch their reactions to this one (it's hilarious):

Then watch one that was on youtube's main page (dog watching tv):