Animals have multiple behavior modes, which we might call instincts or appetencies. Fight, flight, mating, nurturing young, being on alert for predators, eating, resting and hunting are examples.
Creatures in an appetitive condition become less receptive to key stimuli which elicit other behavior patterns. A hunting minded animal must be presented with far stronger sexual stimuli before it makes the transition to mating behavior, and vice versa. As soon as the most pressing impulse has been satisfied, however, the animal regains its normal receptivity to other stimuli.
Lorenz speaks of a “parliament of instincts” – an extremely graphic metaphor. Just as members of a legislative body compete to submit their proposals and put them into effect, so instincts jostle for a chance to take the floor and issue their coordinated commands. They wait to take charge of the body and control it. If no such opportunity presents itself, heightened excitation results: The instinctive act in question becomes easier to elicit and can even take place at random and without special incentive.
Lorenz compares this process of mounting excitation with a liquid gradually rising inside a vessel until it finally overflows. Tinbergen and von Holst also refer to the internal damming of energy specific to action until it eventually spills over. Another graphic idea used to illustrate this process was borrowed from physiology, which speaks of a lowering or raising of stimulus thresholds. The higher a threshold, the harder it is to cross, and the same metaphor has been applied to stimuli which elicit instinctive actions or reflexes. A rise in the stimulus threshold signifies that correspondingly stronger stimuli are required to elicit the appropriate reaction. A fall entails that a relatively small stimulus can cross the threshold and eliminate the block.
The specific mechanisms that increase the influence of a particular instinct have been studied with some success. E.g.:
it is lengthening hours of daylight that put the male stickleback into a procreative mood
and
One example of an internal influence is the operation of hormones. It has been ascertained that when the female collared turtledove sights a displaying male, its ovaries release progesterone into the blood. The effect of this hormone is to arouse a disposition to brood somewhere between five and seven days later. Lehrmann, who experimented with eighty pairs of these doves, injected them with progesterone seven days before bringing the males and females together. When he offered them eggs at the same time as he brought them together, the pairs immediately embarked on brood-tending activities, which they would not normally have done. This was yet another instance of the ease with which instinctive behavior can be distorted and diverted from its natural course-in other words, of its rigidly mechanical nature. In this case, inclination was induced by a hormone. Introduce this into the bloodstream prematurely, and the instinctive member gains ascendancy correspondingly early.
The build up of hormones is one of the mechanisms controlling which behavior pattern an animal does. The more the meter (hormones or whatever) builds up to favor a particular instinct, the more some parameters are relaxed for doing it, e.g.:
Surrogates, or substitutes, are also employed as a means of working off appetencies. This can be seen in creatures which live in communities and among which the mutual grooming of fur and skin forms part of the innate behavior repertory. Keep such creatures in isolation and they will lack the opportunity to carry out these actions. Hence, they will often invite their keeper to let himself be groomed by them. Again, female rats are in such a strong retrieving mood (“retrieving” is the term applied to the instinctive act of salvaging young which crawl out of the nest) for some days after giving birth that they frequently use their own tail or one of their hind legs as a surrogate. They pick up their tail, carry it into the nest, and deposit it there; or they grip one of their hind legs and hobble back with it on three legs as if it were a baby rat.
When a female rat drags its baby back into the nest, that lowers the brood-tending meter (gives it a weaker voice in parliament, or lowers the amount of liquid buildup in the other metaphor). If there are not babies to drag back, the meter gets unusually high. This results in being less discriminating about what looks like a baby. This is a reasonable feature: if what the rat is doing isn’t working, it should relax the constraints on the behavior. It’s also something that can easily be coded without intelligence. Like if you have a visual analyzer that scores objects near the nest for how much they look like a baby rat, you can just lower the threshold for action from a 0.6 score to a 0.4 score. (Presumably it’d be gradually lowered as the meter for doing the brood-tending behavior goes up, rather than lowered in one big jump.)
With this kind of mental model of what’s going on, it’s unsurprising for separated cows and calves to fail to do some instinctual actions, have the meters for those instincts rise, and then do less discriminating actions like:
Bucket-fed calves offer a" similar example. They develop the habit of sucking other calves or the rings on their stall chains.
Or, failing to find substitute actions, a “something is wrong” type meter will go up, and the cow will do behaviors related to that pattern of actions, such as making vocalizations that communicate something negative to other cows (particularly the mother, who might hear the calf and come – in the ancestral environment, calfs being lost would be a common source of various soon-after-birth instinctual actions not being done enough, and calling out would help fix that problem).
This kind of mechanism falls within present day programming abilities. It’s basically just keeping a floating point variable for each major behavioral pattern or mode, and doing behaviors for whichever one has the highest number currently (it’s probably more complicated but that’s a reasonable approximation). Then you need to code some triggers for the variables going up or down, such as hormone levels going up or down, giving birth, or or daylight hours lengthening or shortening. Some of them should go up over time and go down when the behavior is done.
Von Holst and von Saint-Paul acquired even deeper insights into this problem by cerebral stimulation in chickens. Having introduced electrodes into the brain by surgery, they were able to probe individual centers and stimulate them artificially by means of weak electric shocks. This enabled them to tell which form of behavior was controlling the current nerve structure. The tiny electrodes caused the birds no pain or discomfort. When they recovered from the anesthetic, they were completely unaware both of the electrodes and of the gossamer-fine wires emerging from their heads.
The results of these experiments in stimulation were very informative and are recorded in instructional films. One of these shows a cockerel seated contentedly on a laboratory table. Stimulation of a particular part of the brain ensues. At once, the cockerel stands up and starts to peck at the tabletop. There is nothing there to pick up, but as soon as the relevant spot is stimulated, the cockerel pecks like an automaton. Stimulation of another spot results in the cockerel’s remaining seated but looking around. When the voltage is increased (approximately from .1 volt to .3 volt), the bird stands up and starts to cluck. A further increase in voltage and it walks about and evacuates. Yet another increase and it turns around, squats down, and points its beak in a certain direction. Finally, at about .9 volt, it takes off, emitting a series of cries. In this case, gradually increased stimulation elicited various hereditary coordinations in regular succession. In fact, the cockerel exhibited all the behavior patterns with which it would normally have greeted a potential invader of its territory. When von Holst stimulated the calm, seated cockerel with .9 volt right off, the intermediate phases disappeared and the bird flew off screeching. If he stimulated the same points several times, the result was exhaustion and a raising of the stimulus threshold such as can be observed under natural conditions.
Von Holst and von Saint-Paul were able to induce almost any hereditary coordination in poultry by artificial means. It turned out that many hereditary coordinations can be activated from a variety of points in the brain. One example was clucking and another walking. These hereditary coordinations occupy a very subordinate position within the hierarchy of instinctive movements and come into operation in the course of various behavior patterns. For instance, clucking is a concomitant of brood-tending behavior, as well as of the activated urge to flee. Again, the hen walks, or takes steps, not only when in quest of food but also during aggressive action and copulation. Lorenz christened these very simple hereditary coordinations “tool activities” because they are useful for various purposes. It is evident that the circuits in the brain are so disposed that various instincts make use of these basic movements, each within the context of its particular motor flow.
Poultry have a fixed number of actions, like clucking, turning their head or taking a step. These are hard-coded in their brains at particular locations. They do them in fixed sequences as instinct meters rise. Animals are often extremely inflexible and inhuman with following fixed sequences, showing no understanding of what they are doing or its purpose, and just acting like an algorithmic automaton. E.g.:
Sticklebacks migrate in shoals from their deep winter quarters to warmer, shallower waters. Once there, every male seeks a weed-stocked spot and establishes its territory. Only then does it put on mating dress and become receptive to other stimuli. If sticklebacks are captured during migration and placed in a basin which contains no plant life of any kind, they remain in a shoal and do not change color, simply because none of the males can mark out a territory of its own. Plant some weed in one corner, on the other hand, and one of the males will soon detach itself from the rest, take up station there, establish its territory, change color, and become procreatively inclined. In this case, therefore, the growth of procreative inclination is brought about by two factors of an external nature: first, lengthening hours of daylight; and second, the discovery of plants which lend themselves to the establishment of a territory (and nest building).