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.

References

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