As per the author, the muscular effort we make is

Directions: Read the following passage carefully and answer the given question:

One of the most potent elements in body language is eye behaviour. You shift your eyes, meet another person's gaze or fail to meet it and produce an effect out of proportion to the trifling muscular effort you have made. When two people look searchingly into each other's eyes, emotions are heightened and the relationship tips towards greater intimacy.
In normal conversation, each eye contact lasts only about a second before one or both individuals look away. Because the longer meeting of the eyes is rare, it is weighed with significance when it happens and can generate a special kind of human-to-human awareness. Most of the time, a lingering look is inter­preted as a sign of attraction and this should be scru­pulously avoided except in appropriate circumstances. A young woman once complained. ‘That man makes me so uncomfortable, half the time when I glance at him he's already looking at me - and he keeps right on looking.'
Proper street behaviour requires a balance of at­tention and intention. You are supposed to look at a passer-by just enough to show that you are aware of his presence. If you look too little, you appear haughty or furtive; too much and you are inquisitive. Usually what happens is that people eye each other until they are about eight feet apart, at which point both cast their eyes down.