A foundation in music theory will change the way you process and perceive music that you hear. Developing your ear will improve your bass playing. Just like a great writer can get better by reading the classics, a musician can improve by listening to excellent music. To further your understanding, consider setting up a home studio and recording your own music before playing it back. As you train your ear to listen for details in the music, like what key it is in, or why a particular succession of notes sounds good, you will be training yourself to be a stronger bass player.