 Direct studies on sentence spacing include those by <unk> , Branch , <unk> , and Ali ( 2002 ) ; Clinton , Branch , <unk> , and <unk> ( 2003 ) ; and Ni , Branch , and Chen ( 2004 ) , with results favoring neither single , double , nor triple spacing . The 2002 study tested participants ' reading speed for single and double sentence spaced passages of on @-@ screen text . The authors stated that " the ' double space group ' consistently took longer time to finish than the ' single space ' group " but concluded that " there was not enough evidence to suggest that a significant difference exists . " The 2003 and 2004 studies analyzed on @-@ screen single , double , and triple spacing . In both cases , the authors stated that there was insufficient evidence to draw a conclusion . Ni , Branch , Chen , and Clinton conducted a similar study in 2009 using identical spacing variables . The authors concluded that the " results provided insufficient evidence that time and comprehension differ significantly among different conditions of spacing between sentences " . 
