It is the physiological element that separates an emotion from a mere thought. The emotional memory can communicate directly with the neurons responsible for a physiological response. When alerted to danger, a chemical signal causes the release of hormones, including adrenaline, which raise the heart rate, increase respiration, dilate the pupils, slow down digestion and allow muscles to contract to a greater degree than normal, thus increasing speed and strength. The neurons that created this physiological state are wired into the emotional memory so that if the memory is activated, these neurons fire and the body is instantly returned to readiness. There is no interpretation, it is a reflexive firing of neurons.
Charles Darwin recounted an experiment involving a snake in his book, “The Expression of Emotions in Man and Animals”. He placed himself behind a pane of thick glass, determined not to flinch when the snake attacked. In his own words:
“I jumped a yard or two backwards with astonishing rapidity. My will and reason were powerless against the imagination of danger which had never been experienced.”
Clearly an automatic reaction such as Darwin had could save your life. Building on this, several psychologists suggested that emotions, how we feel, are driven first and foremost by interpreting what has already happened in the body. Thus, it is not because we see the snake that we become afraid, we become afraid because we recognise that our rapid heart rate means that there is danger. Emotions are therefore an interpretation of ourselves rather than the environment.
At first this may seem to defy common sense. Yet, we know that a sure-fire way to feel happier is to smile and that walking around with drooping shoulders will depress you. The body affects the mind. On the other hand, this would seem to suggest that we could only become emotional about things that we have already encountered. That a trigger between the event and the physiological response is already in place.
The reality is that the physiological response, and so the emotion, can be automatic or based on interpretation. I may only recognise danger by connecting several pieces of information. There is interpretation before an increase in my pulse. If the experience is sufficiently intense or is repeated in the future there may be an automatic triggering and the body reaction precedes the recognition.
Whether the trigger is automatic or learned there appear to be a number of innate, universal physiological responses that vary according to the emotion experienced. Your body reacts in a different way when you are sad, disgusted, joyful, angry or afraid. But each pattern of reaction is fixed. When you are afraid a certain cluster of cells will be activated, whatever the cause of the fear. Recent research using advanced electronic equipment has shown that the same areas of the brain ‘light-up’ when we experience social fear as when we feel threatened physically. A lion and rejection by a friend, admittedly at differing levels of intensity, activate the same neural circuits.
In early societies facial expressions and gestures were important for communication and the physiological state, angry face and aggressive stance, would be encoded in the emotional memory with the situation and the positive feeling afterwards. There are physiological responses (blushing, narrowing of the eyes, raised eyebrows, increased heart rate etc) attached to all emotions. Even when we believe ourselves to be unobserved, we cannot help but show how we feel. If you think of a happy moment, there is the possibility that your face will betray traces of a smile. Or you may purse your lips when thinking of something distasteful. Often we are able to suppress these reactions but researchers such as Paul Ekman have identified microexpressions, very small movements that are beyond our control, that point to an underlying emotion.
 This is known as the James-Lange theory after the two psychologists who first, independently of each other, suggested this cart-before-the-horse idea.