Stereotypes and Representative Heuristics on the MRT

This happened on Saturday evening when I was taking the MRT from Outram Park to Redhill Station. I saw a couple in front of me, but their backs were to me.
From the back, their physical appearance was quite normal. The man was casually dressed, pants and a polo t-shirt, had greying hair, and looked about fifty-ish. The woman was wearing a white dress and had long hair tied in a pony tail.
What attracted my attention was their behaviour. The woman was clinging on to the arm of the man, somewhat like those young couples who had just fallen in love. The man’s body language was quite nonchalant whereas the woman was almost leaning on his arm.
Remember these observations were from their backs.

They were waiting for the same train at another door, so they didn’t board at the same door as me.

At Tiong Bahru, just one stop later, the door that I was standing at opened for passengers and that man hopped in from the platform. The woman was on the platform, and waving good bye to him. She was quite reluctant to leave. This can be observed from the way she waited until the door closed, and only when the train started to move, did she start walking away. All this while she was waving goodbye to the man.
When she was on the platform I saw her face for the first time. She wasn’t much younger than the man, maybe about 40 or older?

It appears that earlier the couple had boarded at another door and were in the next cabin on the train during the journey. They had alighted at Tiong Bahru. The man had gotten off the train with the woman to 'send her off the train' but had hopped back on the train in my cabin at the door I was at as his destination was not Tiong Bahru. The woman however was going to Tiong Bahru.
Observing their behaviour led me to conclude that this couple, or at least the woman, was quite ‘in love’ with the man.

I only got a closer look at the man when he hopped in at my door. He really had greying hair, and a paunch, typical of middle aged men. And he was also wearing clothes that men of that age normally wear.

I had quickly stereotyped the couple.

This man had the characteristics of the typical middle aged Singaporean man. He was middle aged, had a paunch and greying hair. Applying the representative heuristic, he probably had a family, with children who were teenagers or even young adults. He looked Singaporean, and Singaporean men of that age typically had families already.

Typical middle-aged Singaporean married couples are not love- dovey. Most do not even walk side by side, much less hold hands or indulge in long romantic good-byes. This is a sterotype as well.

Thus I concluded in my mind, the woman was not his wife.

And of course, since there is limited information available, the ‘story’ in my mind may not even be accurate, but I had already formed my own impression and biasness against them in my mind.

This is potentially harmful and even dangerous, since a judgement was passed on them based on mere observations and not the truth or facts. Just like in the case of Amadou Diallo.