One study found that extroverts were more tolerant of typing mistakes than introverts. Personality characteristics&colon; Extroverts have been shown to outperform introverts in computer mediated groups. Moreover, extroverts use a greater variety of power tactics than do introverts. Later research suggests that extroverts and introverts likely have different "arousability". Eysenck found an association between memory and the arousal of introverts versus extroverts. This variation allows for an environment that supports extroverts and introverts. For example, according to type theories, there are two types of people, introverts and extroverts. Introverts have lower social engagement and energy levels than extraverts. Extraverts simply report experiencing more positive emotions, whereas introverts tend to be closer to neutral. Introverts need less stimulation, and more time alone than extraverts. Extraverts are more likely to prefer more upbeat, conventional, and energetic music than introverts. Extraverts and introverts have a variety of behavioural differences. One question that has been posed is why extraverts tend to be happier than introverts. This finding implies that extraverts' positive moods last longer than those of introverts. Firstly, it was found that extraverts were happier than introverts even when alone.