I remember cockles as a childhood treat. My mom would buy them from the market, we'd scald them in boiling water, and eat them plain.
Then came the fear of hepatitis, and suddenly all shellfish was suspect. We stopped eating cockles, I started ordering "cha-kway-teow, mai ham" (without cockles) and years went by without me eating a single one.
They still had a special place in my heart though. In Fast Food Nation, Eric Schlosser talks about children imprint on MacDonalds (in the same way baby birds imprint on their parents) and grow up associating it with happiness and childhood contentment. In the same way, cockles are strongly linked to pleasant memories of my childhood, which is why it was nice to finally eat them again after such a long time. (having had a hepatitis jab in the intervening years between childhood and middle-age helped to allay some of the fears)