Listen but shrewdly

Today I was traveling to office, by train. The ladies compartment was almost empty. I usually open novel while I am traveling but today I was not in the mood to read. So I was just having a look around. But I know  I sometimes I do it badly. That's what happened today. Two girls were sitting to my right. After meeting over a long time, they had enough to talk about. And I was listening, not shrewdly but stupidly. The girl looked at me a few times, every time I realized I am constantly looking at them listening to their talks. I realized that's not the wise way. But this happens inadvertently.

I remember once I was traveling with my sis and mom. There was a women's group traveling sharing their anecdotes. I was hooked to their stories and was almost among them, from my side. Suddenly there was a funny joke and I burst out laughing with others. I found they were staring at me. Embarrassed, I tried to look away, and they carried on with their talking. My mom and sis looked at me indignantly as if I have brought them such a shame. If you are listening at least pretend you are not. What's this ha? Now, let's go. It's our station next, whispered my sis and I left grinning, both over the incident and over myself.

P.S. I am elder to my sister. But she seems to forget and snipe me every time she get a chance. But the incident still brings a smile as it plays vividly before my eyes.