Complete the Words

Psychologists have long asked why people sometimes fail to help a stranger in an emergency. In (1)cla____ experiments (2)fr__ the (3)la__ 1960s, (4)resea______ found (5)th__ people (6)we__ much (7)le__ likely (8)t_ help (9)wh__ they (10)beli____ others were also present. Each onlooker assumes that someone else will act, so the sense of responsibility is spread across the group, and often nobody steps forward. Later studies showed that the effect becomes weaker when the danger is clear and serious.