Ah… Halloween! I just sent my kids out to beg for food from strangers. A few years ago, they had decided that they were too old for this, but I guess they are much younger now.
Long ago, well before I was their age, I took my most memorable trick-or-treat trip. Lots of good loot—I think I was dressed in a plastic ghost mask, but I am not sure; that was not what was so memorable about this evening. I don’t even remember what sort of goodies I got…except for one. I do remember a homemade caramel popcorn ball. I ate it eagerly (this was before there was a general paranoia about homemade treats, although not before the rumors of razor blades secreted into apples to await unsuspecting kids…)
Either later that night, or early the next morning, I was in the hospital. Some nasty bug was making the rounds, and I was one of three kids from my school who were hospitalized. I was, by far, the worst off; they put me in an oxygen tent, surrounded me with icepacks, used my rear for a penicillin pincushion… and I still had a fever that jumped up and down from a low of 104 (F, or 40 C) to a high of 108 (over 42 C). Anyone searching for a cause for my peculiarities need look no further; it is fairly certain that I suffered brain damage from such a fever.
My mom remembers being afraid for my life. The detail that stands out for her was that she (at the time, a medical technologist in another hospital) was given a device to hold while she watched me, a rubber stick to put in my mouth if I were to have a seizure, to prevent me from biting my tongue off. I guess it was a pretty scary situation. I don’t remember much of it at all, and did not remember much of it at the time.
I did recover (surprise!), and remember bits and pieces of a brief recuperation at the hospital. I got toys from some charitable organization, so that my parents would not have to take time to go home. I watched daytime television. I rested. I got better.
Afterward, things were pretty much back to normal. I find, with a bit of amusement, that I cannot recall how long I was out of school. It must have been at least a week. There was one lingering effect, though. I no longer liked popcorn. In fact, I hated it. Could not stand the sight or smell or thought of it. I would not eat it. For over 20 years. It was not until my daughter decided we needed to plant popcorn in the garden—and you know how I feel about eating food from my garden—that I once again could eat popcorn without a feeling of nausea. Today, I am once again able to eat popcorn without worrying, although it is still not my first choice.
The science behind it…
In most cases, classical conditioning works best when the conditioned stimulus is delivered just before the unconditioned stimulus. The stimuli can overlap (delayed conditioning) or be separated briefly (trace conditioning), but if the separation is longer than just half a second or so, conditioning is much less effective. (You may also pair the stimuli in reverse order, or present them simultaneously, but those are subjects for another time.)
There is one important exception to the half-second trace conditioning rule. In conditioning food aversions, the conditioned stimulus (food) may be paired with an unconditional stimulus (nausea-inducing poison, microbes, or radiation) that is presented considerably later. The unconditional stimulus may be presented hours, even days later, and the association between the stimuli may still be learned.
In my case, I know that the popcorn ball was not poisoned, or tainted. I know that there was an illness going around my school, and that my classmates who were sick were from other neighborhoods and had not eaten popcorn from that house. Over the years, I learned about the conditioning of food aversions, but that awareness did nothing to make popcorn any more appetizing.
It makes sense, of course, that food aversion would be an exception to the trace conditioning rule. Even if food is tainted, it may take some time before illness sets in. You could easily eat a non-tainted food in the interim. If it were not for the effectiveness of this long-delay trace conditioning, you might not learn to avoid a dangerous food. (In truth, this sort of learning is biologically prepared; the organisms that did not develop this trick did not leave as many offspring as those that did. We are the descendents of the lucky ones.)
That’s it; nothing complicated this time. I need the time—I have to raid my kids’ candy stash.