Strange input from digitalRead, static interference?

I have a student creating a simple LED/Button project, and he claimed his LEDs were turning on/off as he put his hand near them. I thought it must be something wrong with his code/circuit at first but as I dissected his project the erratic behavior continued. I eventually took apart everything, and simply hooked a wire up to a digital pin, and printed the digitalRead from that pin. The wire went into an empty breadboard, and I still got readings of ‘0’ but readings switched to ‘1’ when I moved my hand near the wire at all(not touching it).

I thought I might need an external resistor going into the pin, but it’s not like there was any current flowing into the pin through the wire?

I thought I might need an external resistor going into the pin, but it's not like there was any current flowing into the pin through the wire?

If the pin is INPUT (the default), without the internal pullup resistor enabled (by default, it isn't) and there is no external resistor connected between the pin and ground or 5V, the pin will float. Undefined behavior when reading a floating pin IS the expected behavior.