According to psychiatrist Judith Orloff in an August 2011 "Psychology Today" article, people in lust are more interested in sex than in conversation. Any chat you do have with your guy will most likely be more superficial than meaningful. A discussion of true feelings is unlikely to happen, and if you try to initiate one, he may quickly change the subject. If your guy does not want to get to know you on a deeper level but still wants you around, he is most likely interested in lust.

In his book "Love and Lust," psychoanalyst Theodor Reik notes that someone driven primarily by lust is searching for physical pleasure, while someone who is in love is in search of deeper joy and happiness. A man who is in love with you cares about the quality of the time you spend together. He will want to learn about what makes you who you are, and he will want to get to know you on a deeper level. Emotional intimacy with you will be just as important to him as physical intimacy.

Orloff states that if your guy wants to leave soon after having sex, he is more interested in lust than love. Because he already got what he was after and is not interested in building any sort of relationship with you, sex will satisfy his urges and leave him ready to go home. The next time he contacts you and wants to get together, you will know what is on his mind and what to expect.

If your guy talks about including you in his future, he is most likely falling in love with you. According to psychiatrist Keith Ablow in an article on the WebMD website, basic animal attraction is a force that designed us to mate, but not for life. A man who wants to keep you in his life for a while has connected with you on a deeper emotional level and wants more than the fleeting pleasure lust brings. If he were solely interested in your body, long-term plans for the future would be the last thing on his mind.