ISFPs are the first to hear the different drummer. Many eagerly plunge into new fashions, avant garde experiences, 'hip' trends--some even setting the trends.
More in touch with the reality of their senses than their INFP counterparts, ISFPs live in the here and now. Their impulses yearn to be free, and are often loosed when others least expect it. The ISFP who continually represses these impulses feels 'dead inside' and may eventually cut and run. (One ISFP friend has become non-ambulatory within the past few years. He will still, on impulse, leave home in the middle of the night and go to Las Vegas or wherever, regardless of the difficulties of his physical condition.)
ISFPs may be overly ingratiating in an initial acquaintance, often complimenting others without basis or substance. Many later become fiercely competitive, especially in sport or table games, and may have great difficulty losing. This competitive nature, also seen in other SP types, sometimes fosters 'lucky,' 'gut' feelings and a willingness to take risks.
Organized education is difficult for the majority of ISFPs, and many drop out before finishing secondary education. Their interest can be held better through experiential learning, at which many excel. ISFPs will practice playing an instrument or honing a favored skill for hours on end, not so much as practice as for the joy of the experience.
Differential diagnosis: ISFPs are less fantasy-oriented than INFPs. These types are often confused, however, INFPs lean strongly to daydreams, poetry, prose and more philosophical pursuits; ISFPs often live out 'id' experiences rather than writing or even talking about them.
ISFJs are driven by the conventional, by 'should's and 'ought's; ISFPs internalize their Feeling (by nature a judging function) which bursts out spontaneously and leaves as quickly and mysteriously as it came.
Because of these variant expressions of Feeling judgment, ISFPs are sometimes confused with ESFJs, but keep themselves more aloof, more often concealing the feelings that ESFJs are so apt to expose.
ESFPs express thoughts more readily (and, in the main, skillfully). ISFPs can and do perform admirably in the spotlight, but generally have little to say about the performance. For example, few ISFPs would be disc-jockeys, a field strongly represented by ES_Ps.