You have four electric motors in the seat.
I would think that each motor controls one movement. You apply power to a motor, and it runs one way, you reverse the polarity, and it runs the other way.
See if the color of the wires at each motor corresponds to the color of wire at the plug. If it does, try hooking the two wires up to a 12 battery, (with a fuse) and see what happens.
See if you can identify what two wires control the four functions, and make a chart for yourself.
This is generally how reversing electric motors are hooked up. When you move a switch, it grounds one side of the motor, and applies power to the other side. Move the switch the other way, and it grounds the side that was hot, and make the side that was grounded hot, and the motor goes the other way. Sometimes, two relays are used for switching the motors. If this is the case, the relays are wired so that both relays ground both sides of the motor. When you move a switch, it switches one relay, and the wire on that relay, going to the electric motor, is switched from ground to hot, and the motor runs.