Conditioned Food Aversion or What Happened When I Poisoned the Family Dogs

I was 10 years old when I poisoned the family dogs.

By that age I had decided my older brothers were doing it wrong; they never kept to a fixed schedule. I figured since mom always fed the family at the same time, the dogs deserved the same treatment and I took over the responsibility.  

Packing for a family trip for a long weekend – we fight about the exact date – I was preparing the dogs’ provisions for the trip when I dropped some water in the main storage container. I thought nothing of it.

When we returned home, I filled their food-dish from the container; the boys gave it a sniff but ate it. 

Thirty minutes or so later the guys started retching and vomited stomach contents. Both dogs recovered and by dinner time were happily devouring mom’s ‘hospital’ ration of boiled chicken with mashed sweet potato and white rice.

Come morning with a brand new bag of the usual, the dogs were offered breakfast and haughtily refused and again refused it for lunch and dinner. They got a new brand of dog food the next day. The boys would never eat that brand again.

It would take a few – or more – years to realize this was my first experience with conditioned food aversion / conditioned taste aversion (CFA).

CFA is a special case of Pavlovian conditioning. In the more familiar form of Pavlovian learning, the animal requires repeated exposure to stumuli with short interval between stimulus and response. In contrast, CFA can develop after one exposure and even after long periods between CS and US. CFA is also highly persistent and resistant to extinction.

I was recently reminded of this experience during the holidays when I came upon a dog I had presumed dead.

Last spring I saw a woman I recognized with a dog I didn’t. As they got closer and I got a better look at the dog and immediatly thought “cachexia… cancer… this dog is going to die.” This young Labrador – whom I knew as slightly overweight – looked like skeletal death.

The owner explained her dog had cancer (obvious) and it was undergoing treatment.  The problem was that he wasn’t gaining weight and would stop eating following his treatment cycle. She knew I was some sort of scientist and asked for advice. As she explained further, I thought it might be CFA because of the nausea which often comes with cancer therapy. [Her vet should have told her this stuff]

Dogs (and people) undergoing chemotherapy can develop food aversions from the nausea that often accompanies intervention. Weirdly, knowing drugs are responsible for the nausea does nothing to ameliorate or prevent CFA. It’s one of those ancient systems that by-passes higher order thinking.

A similar thing can happen under ‘natural’ conditions. If you’ve ever felt sick after eating at a particular (especially new) restaurant or new food, you probably don’t try it again. Lab, rats made sick with LiCl respond the same way – if they feel sick after eating something, they don’t go back to it.

I was able to vaguely recall the details of one study that introduced a novel food before chemotherapy (i.e. meal – novel item – chemo); the patients did so develop an aversion to their meals.

I suggested giving the dog a sampling of something it had never eaten before treatment and after its normal meal. The human study was the only one that came to mind however because it appears to engage such an ancient neural system I assumed (and hoped) it might also work for dogs.

When I saw him again over the holidays, he looked like a different dog. He was now at a healthy weight, moving with ease and vigour and had a shiny coat of brown fur. The owner thanked me profusely for the advice saying my idea worked miracles. In reality I didn’t do anything and the credit goes to science and its application in the form of modern medicine.

My advice was impromptu and offered with zero research. Her overt and disproportionate gratitude made me feel guilty. Had I fed her nonsense? I had to look it up.

I found the paper in question; a 1987 study in which children were given a test meal and then candy before their exposure to chemotherapy.  Introducing the candy between meals and chemotherapy interfered with the acquisition of food aversion and children were twice as likely to eat the test meals compared to the control group. They called it scapegoating.

Apparently it may work with dogs too.


Broberg DJ, & Bernstein IL (1987). Candy as a scapegoat in the prevention of food aversions in children receiving chemotherapy. Cancer, 60 (9), 2344-7 PMID: 3440241

11 thoughts on “Conditioned Food Aversion or What Happened When I Poisoned the Family Dogs

  1. The person and her dog is lucky. My immediate thought was, as you pointed out, it’s a shame her vet didn’t know this. I think it’s a good example why we need to be informed ourselves as well as have others to rely when we need help. 😎

  2. I’m a vet tech and I especially hate introducing a new diet in the hospital for cats. They are masters at food aversions. But it’s tough to convince the doctors, who disregard the notion. But if you want a lifetime switch of food for a cat due to a particular health problem, making the switch in the hospital is the wrong place.

  3. One of our dogs seems to have a general food aversion. She is very suspicious of any food put in front of her and often will back away making a horrified expression. It usually requires offering her bits of food several times before she’ll take the first bite.

    After the first one or two pieces she almost always eats as voraciously as any other dog, but it’s a problem because it means finding someone to take care of the dogs harder.

    Any ideas?

    • Sounds like food novelty is really the issues. Food neophobia is quite normal in many species including humans – though yours sounds lke an extreme case. I’ve never had this problem however you may try a Premack approach and see how that works out.

  4. My dog, Bodhi, became very sick last Thursday, Feb 20, 2014. He had been to doggy day camp on Wed, came home that evening and ate his dinner, went outside for a bit, and then came in and went to sleep as he typically does after an exhausting day at camp. The following morning (Thurs), he ate breakfast and acted as he usually does, but did seem a bit tired still. I left for work at 7:30am and my dad went to pick him up at 9:30 am – he discovered that Bodhi had vomited several times in the house and was continuing to retch. He soon decided to take him to the vet because he was still retching, had started shaking, and refused to drink water. The vet kept him for most of the day to run tests (mainly blood work and x-rays to look for a foreign body). They found nothing – he had a fever and was very dehydrated, but they could not find anything specific wrong with him. They gave him an injectable antibiotic, injectable anti-emetic, and subcutaneous fluids. They also sent me home with a prescription food good for gastrointestinal issues. It has now been 5 days and he is much better, playing, running, tail wagging, and he is hungry and eats – but will barely touch dog food. He’ll eat rice, cheese, crackers, peanut butter, a little yogurt, but only about 2 to 2.5 cups of dog food since last Thurs morning. I’ve tried everything and am at a loss of what to do next. He won’t touch his old food unless it is mixed with the new and covered in beef broth, and he’s not really interested in the new food either. Do you have any thoughts or suggestions? The vet wants me to bring him back in for observation and possibly more tests, but I can’t think of what other tests could possibly help this situation?

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