How are 'facial expressions' in humanoid robots implemented? Can they truly comprehend and express emotions?

Okay, let's talk about this interesting topic.

How are Humanoid Robot "Facial Expressions" Achieved?

You can imagine it as an incredibly complex and precise marionette.

When humans make expressions, we rely on dozens of muscles in our face. For example, to form a "smile," several muscles like the zygomaticus major and orbicularis oris need to work together. Robots mimic this principle, but their "muscles" are a different set of components:

Micro-motors (Actuators): Beneath the robot's soft, bionic skin (usually silicone material), dozens, or even more, micro-motors are densely installed. These motors are the robot's "muscles." Each motor is responsible for controlling a specific small area of the face.
Mechanical Transmission: These micro-motors are connected to key "expression points" on the facial skin—such as the corners of the mouth, eyebrows, outer corners of the eyes, and sides of the nose—through very fine wires, linkages, or other mechanical structures.
Central Processor (Brain): The robot has a central computer. When it needs to make a "happy" expression, the computer sends commands to specific motors according to pre-set programs. For example, the command might be: "Motor #1 at the corner of the mouth pulls up 5 millimeters, motor #2 pulls up 4 millimeters; motor #7 at the corner of the eye contracts slightly by 2 millimeters..."

These motors act simultaneously and precisely, collectively pulling the silicone skin, and a "smile" is born. The more "realistic" the robot's expression, the more internal motors it has and the more complex the control. Some top-tier humanoid robots today can have thirty to forty facial motors, allowing them to produce very subtle and natural expressions.

In essence, robot expressions are "calculated"; engineers program them by breaking down complex human expressions into countless motor parameters, which are then precisely "performed."

Can They Truly Understand and Express Emotions?

This is a more fundamental question. The simple and direct answer is: No.

Everything robots do currently is "simulation," not genuine "understanding" and "feeling."

How Does It "Recognize" Your Emotions?

Robots collect information through sensors like cameras and microphones. They "look" at your face, analyzing features such as the angle of your upturned mouth, the shape of your eyebrows, and the degree of eye opening. Then, they compare these features with tens of thousands of "happy," "sad," or "angry" image data points in their database, finally assigning a label to your expression, such as "Happy: 85%."

At the same time, they also "listen" to your voice, analyzing your tone, speed, and volume to aid in judgment.

This entire process is based on pattern recognition and big data. It knows that "this facial feature + this sound" is defined as "happy" in its database, but it doesn't inherently know what "happy" feels like.

What About Its "Expression"?

When the robot recognizes that you are "happy," its program triggers a corresponding behavior. This behavior, as we discussed earlier, involves calling the "happy" expression program, making the facial motors move to give you a smile.

This process can be understood as a very complex "if...then..." logic:

If it recognizes the other person's expression as "happy."
Then it performs the "smiling" action and says in a friendly tone: "I'm glad to see you so happy!"

As you can see, its response is pre-set, a programmed social interaction. It smiles at you because its program tells it that this is the "correct" reaction in this situation, making you feel that it is intelligent and "empathetic."

The core difference is:

Humans: When we see a friend happy, our brain releases dopamine; we feel joy from deep within, and this physiological and psychological feeling drives us to smile.
Robots: Upon recognizing a "happy" visual signal, the computer runs a pre-set script, executing a mechanical smiling action.

So, even though robot expressions will become increasingly realistic in the future, perhaps even "indistinguishable from real," it will always be a highly skilled "performance." It is an excellent imitator, but it has no joys, angers, sorrows, or delights of its own. It can recognize emotions, but it cannot understand them.