Stimulus Stacking

Have you heard of "Stimilus Stacking"? Very often when a person says "my horse spooked out of nowhere" or "he's over reacting/being dramatic", what's really happening is a Stimulus Stack.

See when a trigger of something in anyway upsetting happens it increases the fear and stress hormones within our (or our horse's) bodies. Then it takes TIME for those hormones to come back down to baseline. When a trigger begins to bother the horse, we call this the "threshold for aversiveness" every horse's trigger and level of stress increase for each trigger will vary as individuals, based on their genes and their learning history. So while some horses might find a plastic bag mildly aversive, some might find it appetitive (are there treats inside?!) So its up to the horse's internal chemical reaction about how severe they find this specific trigger.

The problem is when another trigger happens before the hormones have returned back to baseline. It adds on top of the last, it doesn't happen as a separate event as it appears to us. We think "but the scare earlier was half an hour ago, he can't still be bothered", but the hormones have no had time to reside yet. Each horses' rate of recovery will also vary, based on their self confidence and optimism in general, as well as whether the follow up includes just an abscense of aversives (this will be slow) or the addition of good things that comfort them (which speeds up the recovery process). So if a small concern happens, take time to help the horse return to baseline, to help break down the stack.

So each new stimulus adds on top of the last, resulting in the horse exploding over what may appear to us as a small bother. They may not be very afraid of wind in general, but after 2 or 3 other bothers, now the wind is really getting them stressed. We call this line the "thershold for reactivity", where the horse finally releases their emotions and reacts.

When a horse has been punished for showing signs of fear, the stimulus stack may grow very silently, we won't see the warning signs (because they have been punished), until the horse explodes from the fear. So never punish fear.