"He can't say anything but 'yes' or 'no', but he can sure cuss when he's mad!" I've been told variations of this statement for years whenever I ask about a client's speech. Sometimes the family thinks it's funny and is not concerned about it, other times the family may be mortified and afraid of what others are thinking about it. This article is to address the latter caregivers.
No one really knows why cursing is, of all speech, more preserved in aphasia. Even for persons who didn't curse a lot before the stroke, caregivers may be shocked to find their loved one cursing when frustrated. An educated guess would be that cursing is somewhat 'automatic' speech. Automatic speech is very common in aphasia, so that sometimes it seems as though the person with aphasia can speak better than they really can. Automatic speech can be something such as "hi" when seeing someone, 'hello' into the phone, 'I don't care' or 'wait a minute'. It can also apply to social situations, so that on the surface, the person with aphasia can exchange greetings.
Automatic speech is called automatic because it's something the person says without thinking about it. It just comes out naturally. Since it may not be something that they are consciously saying, they can't really control it. This can become embarrassing for some families, especially in public, church, or around children. Whenever the person with aphasia gets upset, a string of curse words may fly out!
It's typically considered more acceptable to curse when you're an adult than when you are a child, so in one aspect, this can be a normal response to frustration. Some people with aphasia have difficulty with controlling their emotions, especially anger. The stroke has an effect on the brain chemical balances. They may already be very angry about the stroke, aphasia, and how different and unfair their lives are now. It only takes another straw, no matter how small, to break the camel's back.
In the end, you cannot really control another person's behavior—trying to do so leads to a lot of unhappiness. The only suggestion I have may be to try to teach a different word to substitute while in public, such as "shoot" or "rats", but this may prove difficult since you're trying to get them to do this consciously. You can bring awareness to the person with aphasia, such as saying "you just yelled 'sh**' in front of a bunch of children and it was embarrassing, can you try to keep that a lot quieter?" Someone else's behavior does not reflect upon you, and while it may be inappropriate at times, I think the best way to cope is to just laugh about it and apologize to offended parties if needed "she has aphasia and she just curses sometimes. Sorry".