To begin with, some animals – both in the past and in the present – obtain their prey without any particular effort (much like some people have food handed to them on a plate!). A prime example is the tiny coral polyps responsible for creating the gigantic reef structures in tropical seas. They are firmly attached and rely on water currents to sweep microscopic life forms directly to their mouths “free of charge”. Once such a planktonic organism brushes against the ring of tentacles surrounding the mouth, small cells in the tentacles discharge tiny poison darts that paralyze and secure the prey. The tentacles then transport the plankton through the mouth opening into the sac-shaped gut, where it is digested. In our terminology, the cell association known as a coral polyp extracts the energy stored in the molecules making up the plankton that ventured a bit too close. The indigestible remains are ultimately returned to the sea through the mouth opening.

This highly effective feeding strategy has enabled these simple polyps to survive to this day. 1200 million years ago, similar sac-shaped organisms gave rise to the first worm-like creatures that crept over the bottom or through the sand in search of prey. These forms developed a posterior opening of the digestive tract so that the mouth no longer needed to double as an anal pore (Fig. 4). Several such worm-shaped groups ultimately gave rise to the first fishes (urochordates and jawless fish) that swam with long, soft fins that developed from skin folds. Some of these fishes, which continued to evolve and radiate, successfully conquered land about 350 million years ago and began to feed on the plants that had established themselves earlier. Gills proved to be inappropriate for gas exchange in this new environment because they dried out. Instead, breathing – which is necessary in order to digest food – took place in the highly vascularized tissue in the roof of the mouth. Over time, this tissue invaginated, forming sacs on both sides; these in turn underwent a folding process that eventually led to lungs. This development sounds fantastic, but can be irrefutably verified based on fossil remains, on comparisons with transitional forms that still exist today, and based on stages of our own embryological development.

Before we discuss the features that fundamentally distinguish us from this ancestral fauna, it is helpful to examine how the psychosplit developed in humans. Specifically, what range of strategies does the wondrous animal world use to detect, pursue and strike their prey and transfer it into their bellies. Ethology, or comparative animal behavior, tells us that optimal foraging not only requires nimble limbs and sensitive sensory organs, but also highly developed mechanisms that control movement.

First: all active hunters must be able to isolate the relatively few prey-related sensory inputs from the overall cascade of incoming signals. The innate circuitry of their nervous systems must enable immediate responses to certain “key stimuli”.

Second: these key stimuli must trigger efficient predatory activity. Once the caterpillar reaches a suitable leaf, its body and feeding movements must be coordinated so that it can crawl along the leaf while biting off piece after piece. Once the predatory fish detects its prey, its brain must send coordinated commands to the respective organs to efficiently pursue, dispatch and devour it. The sensory inputs – vision, smell, hearing, touch, taste – must continuously control and correct the animal’s movements. This overall performance, which relies on innate circuitry and switches, is known as “fixed action patterns”. Depending on the prey’s features and behavior, these patterns can be quite differently developed.

Third: the animal must be motivated for the predatory action. This also applies to every other vital activity such as repelling enemies, mating and brood behavior. If no key stimulus that signalizes prey is encountered over a longer period, then additional commands must motivate the animal to forage more intensively. This third complex is termed a “drive”. When food is involved, we name this condition “hunger”. This internally generated motivation increases the animal’s state of excitation, causing it to spend more time and effort to obtain prey (appetitive behavior). Once successful, these commands are switched off: the goal of the drive has been reached, the hunger stilled (consummatory or end act). For some specified period of time, the animal is free to deal with other vital functions. Drives can be likened to a parliament in which members successively rise from the bench and assume control. This helps the animal to fulfill its crucial functions in orderly fashion¹⁰.

All innate behaviors are known as “instincts”. This is nothing mystical, transcendental, or metaphysical. Rather, instincts are the manifestations of control mechanisms. Although these mechanisms are rooted in an exceedingly complex nerve network and we cannot perceive them as clearly delimited organs, they represent functional units as real as fins, eyes, the liver, or the circulatory system. In all multicellular organisms, the genetic make-up of the germ cells specifies precisely which organs the budding cell associations must build – and this also holds true for the innate circuitry that controls and coordinates the activity of the remaining organs as well as for the body’s overall instinctive response to its environment.

“Learning” is defined as the ability to modify, supplement, and refine innate programs – or to add additional ones – based on individual experience. Even protozoans can learn, and this capability has been perfected in the vertebrates. In mammals and birds, which are particularly talented learners, many innate programs have been reduced; here, the young exhibit a specially developed innate play behavior also known as curiosity behavior. This motivates them to actively engage their environment and to tailor the most important behavioral programs for themselves. The advantage? These animals act and react less like robots and can better adapt to the prevailing environmental conditions. The disadvantage is that such species are not born into this world fully developed, with insects being a prime example. This necessitates a commensurately high degree of protection and care – an additional, “expensive” drive known as parental care.

The response to key stimuli is crucial when we examine feeding in animals and humans. A very simple stimulus, one that triggers this behavior in sharks for example, is the smell of blood. It indicates that another organism is wounded and therefore less capable of escaping or defending itself – making it a trusty signal for the predator. Other fish species wait patiently for insects to fall or land on the surface of rivers or lakes. Here, mechanical vibrations emanating from the broken surface are key stimuli that activate attack behavior. In frogs and toads, optical stimuli trigger predatory behavior. A motionless insect will typically go undetected. As soon as it moves, however, the toad leaps forward and devours it.

Scientists have long used so-called dummy or surrogate experiments to demonstrate how simple or even primitive such key stimulus response mechanisms are. When sticklebacks spawn, for example, the sudden appearance of a rival male fish triggers threat responses and attack behavior in other males. In this case, the red stripe on the male’s belly is the recognition signal or, more precisely, the key stimulus. If the experimenter shows the male a cylinder that lacks eyes, fins or any other fish features but has a red stripe along the lower side, then this is sufficient to elicit the above threat and attack behavior. Simply turn the cylinder over so that the red stripe lies on the upper side, and the fish shows no reaction. The control mechanism in the fish’s brain therefore responds mechanically to the feature “elongate body with a red stripe below”. “Recognition” in the sense of human insight plays no role at all.

Because such automatic reactions often elicit incorrect behavior in employees and businesses, I provide another often-cited example here: in turkeys, the frightened cheeping of chicks is a key stimulus for the mother hen to gather the chicks under her wing. Polecats are important predators of turkeys. Incredibly, installing a transmitter and speaker into a stuffed polecat, and playing back chirps of fright, triggers the hen to take the polecat under her wing. This convincingly demonstrates that such reactions have nothing to do with intelligence or insight.

Note, however, that many animals recognize their prey based on several key stimuli. Sharks, for example, detect a wriggling fish at the end of a harpoon over far greater distances and much quicker than based solely on the slowly dissipating smell of blood. This allows them to appear on the scene within seconds, even from distances of several hundred meters. The sequence of various key stimuli is also often crucial, for example in the courtship behavior of birds. This behavior can involve a “dialog” of key stimuli in which movement A in the male triggers movement B in the female, which in turn elicits movement C in the male, leading to movement D in the female.

A key feature in the present context is that the nerve circuitry of any animal capable of learning (a circuitry which initially responds innately to key stimuli) can be refined and its effectiveness improved. A young toad, for example, snaps at any small body that moves across its path. Such objects are usually insects, and the key stimulus therefore serves the amphibian well. If the young toad snaps at a wasp and is stung, it will never again snap at small moving objects with transverse stripes: the response to key stimuli has become more differentiated and therefore improved. Most learning processes are based on this principle. The term “conditioned reflex” describes the situation in which an animal associates impressions that precede some event, such as feeding, with that event. Thereafter, the preceding impression itself is sufficient to trigger the feeding behavior. This “conditioning” process, which underlies many learning processes and leads to the psychosplit in humans, will be treated in detail later.

Fixed action patterns (instinctive movement triggered by key stimuli) are a similar phenomenon. They can also be changed, improved, or made more effective through learning. In many birds, for example, the basic movements involved in flying are innate, but practical experience is needed to read the wind and safely alight on different substrates or objects. Adult lions or foxes hunt more efficiently than younger conspecifics, and this represents an early stage of “insight behavior”, i.e. exploiting experience. This ability is particularly highly developed in humans and forms the basis for higher-level, intelligent behaviors.

“Drives” form the third large component of innate behavior. They are autonomous and immutable and ensure that animals function according to intended programs. Although they can be changed only minimally through learning, we can partly rein them in, briefly suppress them or even purposefully reinforce them (human sexuality, for example), but never eradicate them entirely. As Freud determined in humans and Lorenz later in animals, unrealized drives can lead to “vacuum activity” or cause behavior to “shift tracks”. Thus, Lorenz observed that a well-fed captive starling fluttered through the air and, although no insects were present in the room, snapped at “imaginary” insects. Its hunger was stilled, but the innate impulse to hunt flying insects had not been satisfied and was manifested as “vacuum behavior”. When two roosters fight with one another – and aggression and fear are equally balanced – then the opponents often intermittently peck the ground as if they were looking for seeds, although this in no way fits their momentary situation. Such “displacement activity” is another mechanism of releasing bottled-up distress.

Humans display similar behaviors in waiting rooms or other settings: their impatience leads them to scratch their heads, pick their noses or let off steam by smoking or munching on something. The terms “displacement scratching”, “displacement nose-picking”, “displacement smoking” and “displacement eating” have been coined to describe such activity¹¹. Freud held the opinion that certain persons who are unable to exercise their sexuality “sublimate” this distress in artistic activity. Here, one instinct prompts activity in an entirely unrelated realm.

Fear is the mirror instinct to the feeding drive. It helps prevent an animal from falling prey itself. This time the prey must recognize the predator based on certain key stimuli and then react appropriately by fleeing, hiding or defending itself. This instinct is the “inner voice” warning against potential danger, for example of venturing into places where it is prone to attack. Clearly, opposing drives like hunger and fear influence one another. Very hungry animals are more likely to exhibit risky foraging and feeding behavior. Conversely, high fright levels will tend to dampen normal predatory activity.

Drives are therefore at the core of every instinct. In a highly complex machinery they direct actions and reactions, motivating the animal to act as needed in that phase of its life. The response to key stimuli can be refined through learning, or be displaced to completely different stimuli. Fixed action patterns, which the animal can improve and adapt to its specific environmental conditions through learning and experience, are also changeable. The difference between specialists and generalists, i.e. animals with very specific feeding types (such as mosquitoes) versus those with a varied diet (wild boars or monkeys), will be discussed in detail later.

The important point in this chapter is that every behavior is based on control mechanisms in the brain; these programs either developed like any other organs through genetically predetermined differentiation of cells, or thereafter through learning processes in the brain. They are exceptionally small, operate somewhere in the astounding maze of the nervous system and are less easily delimited than a bone, heart or eye. Nonetheless, they clearly represent – like all other organs – functional material units¹².
 

Back to the Table of Contents

Continue to "4^th Premise: The unique feature in humans – we develop additional organs"