into lukes head

have you ever wished you could get into someones head in the hopes to better understand where they were coming from? lately, that is how i feel with our middle child, luke. i love my luke and yet find myself struggeling to understand him more times than not. as a parent you learn quickly that you cannot parent each of your children the same way - because they are each so different and in turn respond differently. for as confident as luke can appear on the outside i don't know what goes on his mind to make him incapable of doing certain things. for example, yesterday he woke up and told me that he had decided not to go to his friends birthday party because they were going to go and play laser tag. i was shocked. not only was this a very good friends birthday but his big brother was also going. however, luke had it in his head that he did not want to play and did not want to go. when i asked if it was because he had never played laser tag he said, "no, i just don't want to go....". i told him not going wasn't an option - however, if he got there and still didn't want to play that he didn't have to. sure enough, luke got to the laser tag play area and chose not to play and stood on the sidelines and watched on for the next hour and half as his friends and brother played their little hearts out. what is it...? what, as a parent, can i do to encourage him and help him with his anxiety?

any thoughts.....suggestions.......