Why is there such a big difference between touching yourself and being touched by others?

Layer 1: Prediction suppression: The brain anticipates the sensation you produce yourself and automatically "desensitizes," making the feeling weaker.
Layer 2: Unpredictability: Touches from others cannot be modeled in advance, so the brain automatically heightens alertness and sensory intensity.
Layer 3: Social signals: Touch is not just a physical stimulus; it also conveys relational information—intimacy, trust, boundary crossing.
Layer 4: Control difference: Self-touch is fully controllable; others' touch means you are passively receiving, so sensitivity increases.
Layer 5: Attention focus: When touching yourself, attention is split between performing the action; when being touched, attention is concentrated on the sensation itself.