Some of the more significant findings indicate that number conservation seem too occur in 5- and 6-year-olds earlier than previous findings had indicated (Nelson, 1974), that conservation ogf number precedes acquisition of a class inclusion relation (Kronberg & Winer,1974), and that accurate perception of the cardinality of a set by first graders declines rapidly as sets become larger in size than five (Maertens, Jones, & Waite, 1977).
Counting strategies used by first and second graders have been carefully studied by investigators of PMDC (Denmark, Note 1).
Systematic touching of objects being counted was the most successful strategy used by first graders.
This suggests that objects that can be touched, not pictured objects. should be the things counted