Professor Zuckerman categorised his subjects, a group of American undergraduates, as either 'high sensation seekers' (HSS) or 'low sensation seekers' (LSS) by means of a questionnaire, which tested how easily bored they were; how much they liked sex; how much they enjoyed parties; and whether they liked new experiences. He then studied their reactions to paintings by the English landscape artist Joseph Mallord William Turner (1775-1851), who sought to convey atmosphere by means of innovative use of colour and gradations of light.
Professor Zuckerman found that Turner's Snow Storm, Avalanche and Inundation - a hazy, Impressionistic, semi-abstract picture, seen as being full of tension - was favoured by the high sensation seekers, as was another more realistic but similarly complex picture, Avalanche in the Alps. In contrast, the low sensation seekers preferred his realistic pastoral scenes with little tension, such as View of Clapham Common.
According to Professor Zuckerman, one reason for Turner's popularity may be that he is one of the few artists to appeal to both HSS and LSS types.
In fact, this link between favoured painting style and the two personality types is only the most recent difference to have been studied. It has already been established that HSS people are more likely to become alcoholics, to smoke, to make risky financial investments, to volunteer for combat units in the army and to like watching sex and violence on television and in the cinema.
The reason Professor Zuckerman has been studying them for nearly 20 years is that they make up a section of the population that has an effect greatly in excess of its size. They are the people who make waves.
'These are the people who, if they get the stimulation they need in the right way, can be very useful to society. They are the explorers, the sportspeople, the innovators,' he says. 'But when they get it wrong, they also tend to be the bank robbers, the ram raiders and the people with drink and drug problems.'
Professor Zuckerman believes that much of the debate over sex and violence on television and video could really be a matter of the low sensation seeker objecting to the way the high sensation seekers get their kicks.
The most generally accepted theory of how the two types of people differ involves arousal mechanisms in the brain. HSS people need greater levels of stimulation of a part of the brain known as the Reticular Activating System (RAS), which affects the level of arousal in the rest of the brain. The RAS in the high sensation seekers seems to be more sluggish than other people's, so they are always trying to fire themselves up with excitement or novelty or challenges. There is some evidence that the HSS personality trait is inherited.
So why do HSS people like abstract and expressionistic paintings? Professor Zuckerman says they are happy with the ambiguity of semi-abstract pictures - which tends to make the LSS uncomfortably aroused - while the greater emotional impact of expressionistic paintings is just what they are looking for.
HSS people also take much greater risks with their health. Apart from life- and limb-threatening sports, they are more likely to smoke than the LSS people - although being just as aware of the risks - and are less likely to practise safe sex.
'We are not certain yet why they are more comfortable with risks,' says Professor Zuckerman. 'It could be that once they have tried something they are more likely to become confident that they can handle it, or it could be that they actually feel the pleasures and rewards of what they are doing more intensely.'
There are also suggestions that HSS and LSS personalities have different reactions to chocolate. HSS people have comparatively low levels of an enzyme called monoamine oxidase (MAO), which mops up the body chemicals involved in arousal, such as adrenalin. One of the key ingredients of chocolate is a chemical called phenylethylamine (PEA), which seems to have a rousing effect on people rather similar to adrenalin. PEA is broken down by MAO; less MAO should mean more PEA and therefore more arousal.
But the relationship between these factors is still not fully understood. Two further pieces of research waiting to be done are to investigate whether chocolate has a more lasting effect on HSS types because it is broken down more slowly, and to find out whether HSS people are more likely to become chocaholics than those who metabolise their chocolate more efficiently.
Spotting an HSS type should not be too much of a problem. Look for the surfboard on top of the car, note the string of sexual partners, and possibly observe a sweet tooth. All are likely clues.
But there is another sign which does not depend on behaviour at all. A couple of drops of lemon juice dripped on to the tongue of a low sensation seeker will produce lots of saliva. The high sensation seeker will hardly notice it.