Words of appreciation, encouragement, affection, praise, compliments. Giving and recieving overt verbal strokes is very important to some people. Many of these are individuals who are idealistic, emotional and prefer to make ecisions based on how people will feel more than the cold hard logical analysis of the factual situation. Acts of service. I would not be surprised if this was a very important dialect of your wife, if not her primary mother tongue.
Many structured introverts are heavily into doing for others.
My husband will work, work, work, and keep finding things to do, because it is the only way he knows, or really understands on his gut level, to show he loves us. When he feels bad for have LB'd he washes dishes and laundry. My mother does this too. It can look very cold to someone who needs a lot of touch, affirmations, or conversation, but it comes from the heart. They are more likely to MAKE gifts than to buy them.