It’s the old “book-by-the-cover” thing. Deep down, we live on the surface. That’s apparently a cultural reaction, and it’s a relative matter, as you probably know.
Think dermatologists. They can recognize by appearance something about what might be going on beneath or inside the epidermis. Years of schooling and experience with skin enable them to assess the nature—and health—of not only the outside, but also the inside of a body down through the hypodermis. But when dermatologists suspect an ailment, even one that might lie beneath the surface, they take samples: Biopsies confirm or quash suspicions.
We can learn from dermatologists. It’s okay to get a first impression; the process might yield a warning that danger is imminent. The encyclopedic cultural knowledge that everyone carries makes having a first impression unavoidable.
It’s not okay to live long by first impressions, however. In the absence of imminent danger, take the time to do “psychopsies.”