We've all done it. Halfway through a conversation, the word we want just won't come out. We know it, we're certain that if we just try a bit harder, we can come up with the word.
|Photo (C) 2012 by Steven Frame, Shutterstock|
Actually, no. In most people, temporary aphasia is actually a phenomenon of interference. Our brains are running along in a conversation (sort of like the old joke about engaging the brain before putting the mouth in gear) and we realize that we weren't actually thinking about what we were saying even though the words were coming out of our mouth. When we hit the point of having to say a word that has not be "preprogrammed" we realize that our thoughts have run so far ahead of what we are saying that they are now interfering with the ability to remember and say the word.
It does seem to happen more often as we age, but it's no more a symptom of age-related memory loss than it is one of distraction.
In the last blog, I mentioned the "P300" event related potential that indicates when a subject sees or hears an unfamiliar, unexpected or rare stimulus. When stimuli are familiar, the brain simply does not spend as much time processing them. In 2004, neuroscience researchers R.E. Hampson and S.A. Deadwyler showed that when rats were performing a behavioral test in which the individual trials were familiar and easy, the brain activity in the hippocampus (which processes memory) dropped to very low levels, but as soon as the rats made a mistake or were given a trial that did not match the previous sequence, the activity in hippocampus rebounded. Likewise, their earlier work showed that animals with damage to the hippocampus could still perform a version of the same task (which normally required hippocampus) as long as the stimuli were presented in a familiar pattern with a fixed sequence.
So the brain actually doesn't process as much information when performing familiar tasks. This is one reason why repetition is an important part of learning, because if the brain does need to get involved in routine tasks, they slow down. The drawback is interference. When operating in this "automatic" mode, if we actually stop to think about what we are saying or doing, we realize that we don't have a clear memory record. Thus other memories can interfere - the sentence before last, the action before last - and it results in "tip of the tongue" in speech, losing our place, or stumbling in our actions.
A lot is being made these days about politicians and public figures who make "slips" of the tongue in their speeches. Is it stress, senility, lack of intelligence, disease? Probably not. It's usually interference. The person is simply thinking about something else while they are talking - yet such slips can be quite revealing, because they provide a glimpse into what information is actually foremost in their thoughts - and thus providing the interference.
So, what can we do about resolving the "tip of the tongue" aphasia?
The best thing to do is to stop stressing over it. The more you try to remember the word, the more interference you are placing into memory. Relax, direct your thoughts toward something else, or simply ignore it and continue the conversation. The memory is not totally gone, and you will recall it once you can reduce interference and trigger the appropriate association. I have a colleague with severe aphasia (of the medical variety) - for names and proper nouns - and he frankly uses other people to help fill in the gaps for him. We all know about it, and usually either provide the name or allow him to ignore it and move in. When it is important, it is possible to access the memory by assisting him with making associations with his own memory.
The tip of the tongue is for tasting... and making funny faces. But both the "tip of the tongue" phenomenon and "slips of the tongue" are real disorders of human memory, and can be quite revealing of how (and when) the brain processes information!