Being mentally alert is a state of mind and we are obviously not always alert. Our mood and general level of physiological arousal will tend to range from deep sleep through drowsiness to a normal waking state; occasionally we experience a state of high agitation or excitement, and under extreme conditions, terror and panic. High arousal tends to be accompanied by changes in the electrical activity of the brain as recorded by electroencephalogram (EEG), and by an increase in heart rate, palm sweating and electrical conductivity of the skin. Arousal can also be altered by manipulating the environment or through drugs. Hence loud noises will tend to increase arousal, whereas the deprivation of sleep will tend to decrease it. Amphetamines or the caffeine in a cup of coffee will tend to lead to higher arousal, while a tranquilizer will tend to reduce it. Other drugs such as alcohol have more complex effects, initially increasing but then decreasing arousal.
Do our state of arousal influence our memory? Clearly in an extreme case, it has a profound effect; a subject who is asleep has a very limited performance repertoire. It has been suggested that we are able to learn when we are asleep. Unfortunately objective tests of the effectiveness of sleep teaching suggest that nothing is learned except the few bits of information that are registered during the occasional periods during the night when we approach a waking moment, in between long periods of deeper sleep. If you wish to learn, it is advisable to be conscious at the time.
Any individual can have a very wide range of levels of arousal at any moment, and there is no doubt that performance is sensitive to arousal level. In general, performance improves as arousal increases up to some peak, beyond which it deteriorates, a relationship known as the Yerkes-Dodson law after the two people who first pointed it out Taking the two extremes, neither the moment prior to falling asleep nor the moment of blind panic are likely to be particularly efficient states of mind for the performance of any task. Different tasks are optimally performed at the different levels of arousal. For example, the level at which you are likely to run fastest or hit hardest will be higher than that which is best for knitting a sweater or solving a crossword puzzle.
How can we determine the optimal arousal level for memory? Like much else in human memory, this is not an easy question to answer. It depends crucially on when the learned material is subsequently recalled. If recall is immediate, then performance is best when level of arousal is relatively low; higher levels of arousal lead to poor initial performance, but in the long run they produce better learning.
This was shown most clearly in a series of experiments conducted by Kleinsmith and Kaplan in 1963 in which subjects were presented with the task of learning to associate numbers with words. The words were selected as being either relatively neutral (swim, dance) or as having emotional overtones (rape, vomit). Three groups of subjects were tested, the first recalling after a delay of two minutes, the second after a 20-minute delay, and the third after a delay of one week. The low-arousal words were initially well recalled but showed marked forgetting. Recall of the high-arousal words actually improved with time. Kleinsmith and Kaplan argue that high levels of arousal help the memory trace to consolidate, but that during the early stages of consolidation they make retrieval difficult. The high-arousal items therefore have a short-term they benefit from good consolidation.
Taking these findings a step further, we can therefore remember things better with we attached vivid imagery to it. For example, if you want to remember a dental appointment at 10 in the morning, you can picture a bowling ball coming towards your mouth and your teeth become bowling pins (10-pins – 10 am). Memory strategies have come up that can help people improve memory, learn complex mathematical formula, foreign languages etc. Such memory techniques and memory training are useful not only for school work, but also in our daily and professional lives to help us cope.
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