# 1.4 Infant Emotions
Infants, when suffering even slight pain, moderate hunger, or discomfort, utter violent and prolonged screams. Whilst thus screaming their eyes are firmly closed, so that the skin round them is wrinkled, and the forehead contracted into a frown. The mouth is widely opened with the lips retracted in a peculiar manner, which causes it to assume a squarish form; the gums or teeth being more or less exposed. —Charles Darwin, in The Emotions of Animals
One moment your baby seems perfectly well, but then come some restless motions of limbs. Next you see a few catches of breath—and in the next moment, the air fills with screams. Is baby hungry, sleepy, or wet? Whatever it is, those cries compel you to find some action that will help. It may take you some time to discover the trouble, but once you find the remedy, things quickly return to normality. However, if you’re not used to dealing with infants, those sudden switches in mood can upset you; when your friends cry, you can ask them what's wrong—but talking to infants is fruitless because "no one is home" to communicate with.
Of course, I do not mean to suggest that infants don’t have ‘personalities.’ You can usually sense, quite soon after birth, that a particular baby reacts more quickly, or seems more patient or irritable, or even more inquisitive. Some of those traits may change with time, but others persist through the rest of that life. Nevertheless, we still need to ask, how could an infant change so much between one moment and the next? The Single-Self model cannot explain how suddenly an infant can switch from contentment or calmness to anger or rage.
To make a more plausible model for this, imagine that someone has asked you to build an artificial animal. You could start by making a list of goals that your animal-robot needs to achieve. It might need to find sources of water and food. It might need defenses against attacks—and against extremes of temperature. It might even need ways to attract helpful friends. Then once you have assembled that list, you could tell your engineers to meet each such need by building a separate “instinct-machine.
Then, how could we build those instinct-machines? Each of them needs three kinds of resources: some ways to recognize situations, some knowledge about how to react to these, and some muscles or motors to execute actions.
What could be in that central knowledge box? Let's begin with the simplest case: suppose that we already know, in advance, all the situations our robot will face. Then all we need is a catalog of simple, two-part "If–>Do" rules—where each If describes one of those situations—and its Do describes which action to take. Let’s call this a “Rule-Based Reaction-Machine.”
- If temperature wrong, Adjust it to normal.
- If you need some food, Get something to eat.
- If you’re facing a threat, Select some defense.
- If an active sexual drive, Search for a mate.
Many If–>Do rules like these are born into each species of animals. For example, every infant is born with ways to maintain its body temperature: when too hot, it can pant, sweat, stretch out, and vasodilate, when too cold, it can retract its limbs or curl up, shiver, vasoconstrict, or otherwise generate more heat. [^See §6-1.2.] Later in life we learn to use actions that change the external world.
- If your room is too hot, Open a window.
- If too much sunlight, Pull down the shade.
- If you are too cold, Turn on a heater.
- If you are too cold, Put on more clothing.
This idea of a set of "If–>Do rules” portrays a mind as nothing more than a bundle of separate reaction-machines. Yet although this concept may seem too simplistic, in his masterful book, The Study of Instinct,[^4] Nikolaas Tinbergen showed that such schemes could be remarkably good for describing some things that animals do. He also proposed some important ideas about what might turn those specialists on and off, how they accomplish their various tasks, and what happens when some of those methods fail.
Nevertheless, no structure like this could ever support the intricate feelings and thoughts of adults—or even of infants. The rest of this book will try to describe systems that work more like human minds.