Moral nature can be explored using the same methods as we study other aspects of our mental lives, such as language, perception, and memory.
We can examine moral reasoning across societies, or explore how people differ within a single society—for example, comparing liberals and conservatives in the United States.
We may also investigate unusual cases, such as cold-blooded psychopaths.
Or, perhaps we wonder whether creatures like chimpanzees possess something we might call morality, and turn to evolutionary biology to explore how a moral sense might have evolved.
Social psychologists could study how environmental characteristics encourage kindness or cruelty, and neuroscientists could study brain regions involved in moral reasoning.
This book briefly covers all of these.
But as a developmental psychologist, I have other main interests.
It is a way to explore morality by looking into the origins of morality that infants and toddlers possess.
I would argue that modern developmental research has revealed some shocking facts about our moral lives.

--- From "Introduction_In Search of Morality"

A one-year-old baby decides to take justice into his own hands.
He had just watched a puppet show featuring three characters.
In the play, when the middle doll rolled a ball to the doll on the right, the doll returned the ball.
This time I rolled the ball to the doll on the left, but it ran away with the ball.
After the puppet show, the two puppets on the right and left were taken down from the stage and placed in front of the baby.
A piece of candy was placed in front of each doll, and the baby was allowed to take one of the candies.
As expected, like most of the infants in this experiment, this baby took the candy from the doll that ran away with the 'bad' doll ball.
But he wasn't satisfied with this alone.
So he leaned forward and hit the wicked doll on the head.
What I want to suggest through this book is this.
As a result of various experiments like the above, it has been proven that some aspects of our morality are innate and some aspects are not.
We have a moral sense that leads us to judge others, to feel pity and condemnation.
We are naturally kind to others.
At least for a certain moment.
But we also have ugly instincts.
This instinct can be transferred and turn into evil.
“We are born into this world with a nature full of evil tendencies,” said the 19th-century Reverend Thomas Martin, who spoke of the “innate wickedness” of children, and was not entirely wrong.
--- From "Chapter 1: The Moral Life of Babies: What is Morality?"

I think we are born with a moral sense.
So, I will continue to repeat this argument in this book.
But morality involves much more than just a certain ability to discern.
This includes emotions and motivations such as the desire to help others in need, compassion for those who suffer, anger toward those who are cruel, guilt for one's own shameful actions, and pride in one's good deeds.
[64p, Chapter 1: The Moral Life of Babies: We are Born with a Moral Sense]

Let's take a closer look at what separates psychopaths from the rest of us.
Psychopaths exhibit many symptoms, including pathological vanity and a lack of remorse or guilt.
But the core deficiency among them is indifference to the suffering of others.
They lack compassion.
To understand how compassion works in the minds of all of us, not just psychopaths, it's important to distinguish between compassion and empathy.
Although some researchers now use these two terms interchangeably, there is a significant difference between caring for someone (compassion) and putting yourself in their shoes (empathy).
--- From "Chapter 2 Empathy and Compassion: The Subtle Difference Between Empathy and Compassion"

Justice isn't just about finding the best way to distribute positive things.
You also have to decide how to share the negative.
That's where punishment and revenge, the dark side of morality, comes in.
If we were always kind to each other, the question of punishment would never arise.
But as anthropologist Robert Ardrey has pointed out, “We are not born of fallen angels, but of rising apes.” Some of us are tempted to cheat, kill, and give in to selfish impulses.
The rest of us must make these bad behaviors pay dearly in order to survive in the presence of these people.
Indeed, some scholars, including philosopher Jesse Printz, argue that outrage is more important for morality than the relatively sweet emotions of empathy and compassion, which we discussed in the previous chapter.
--- From "Chapter 3 Justice, Status, Punishment: Punishment, Revenge, and the Dark Side of Morality"

Babies can distinguish between familiar and unfamiliar people almost instantly.
Newborn babies prefer to look at their mother's face rather than a stranger's.
I also like my mother's smell and voice better.
The fact that babies prefer their mother's voice was discovered through an excellent experimental method.
(…) Babies not only like familiar people, but also like people of the same type as the familiar people.
This fact can be explored by using the attention time measurement method.
As mentioned earlier, just like adults, babies look longer at surprising things.
However, the tendency to look at something they like for a longer time is the same as that of adults.
So we can use this to explore babies' preferences.
The study found that babies looked longer at women if the caregiver was female, and longer at men if the caregiver was male.
White babies prefer to see white faces rather than African or Chinese faces.

--- From "Chapter 4: Others: The Roots of Racial Bias"

Babies don't know disgust.
Freud puts it this way in Civilization and its Discontents:
“Excrement does not cause disgust in children.
To them, it seems precious because it is a part of their own body.” When adults look away, babies and toddlers touch all kinds of disgusting things and even eat them.
The Rosin research team conducted this experiment while conducting one of the most fascinating studies in the field of developmental psychology.
Children under two years old were given something that was 'made to look like real dog poop, made with peanut butter and strong-smelling cheese', which they called dog poop.
Then most of the children ate it.
Most also ate small dried fish whole, and about a third also ate grasshoppers.
Then, at some point in their childhood, as if a switch were turned on, children begin to hate many things in the world, just like adults.
Psychologists are very curious about what causes these changes.
Many of them follow Freud's theory and point out that toilet training is traumatic.
--- From "Chapter 5 Body: Why and What Do Humans Hate?"

Many of the actions we consider good deeds are so ingrained in our culture that we do them without giving them much thought.
This is similar to learning to speak.
When a two-year-old learns that a dog is called "dog," they usually don't question why it's called that or why everything has a name.
These are good questions that your child may wonder about as he or she grows up.
However, because infants and toddlers have to learn so many words, they simply follow what others do and do not understand the logic behind it.
In fact, much of what we learn is learned unconsciously.
For example, I was raised that way at home, so I prefer to keep some physical distance from other people.
But the only time I'm conscious of this is when I'm around people who were raised differently than I was.
It's like how we only become aware of something we say in English as "things" when we hear speakers of other languages ​​use a word other than "things."

--- From "Chapter 7: How to Become a Good Person: Altruism as a Part of Custom"