Tech points are produced only for duplicates of the collectibles that have already been found; the first one of each type is added to your Collections Screen. The way to tell whether or not you'll get tech points for a collectible is to watch the message at the bottom of the game screen when the children pick up a collectible. If it says that it's new, you won't get tech points; if it says that it's for the scientists, you'll get tech points.
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