Studies of poor comprehenders vary in the selection criteria and tests that they use to define poor comprehension. Could these differences play a role in determining findings about poor comprehension? This study assessed the extent to which differences in selection methods affect who gets identified as poor comprehenders, and examined how their cognitive profiles differ. Over 1,500 children, ages 8 - 19, took multiple tests of reading comprehension, listening comprehension, single word reading and nonword reading. Poor comprehension was defined by performing in the low-tail and by discrepancies either with word or nonword reading. Odds of any two selection methods identifying the same individuals were generally low, and depended on type of comprehension test more than modality, as well as selection criteria, and comprehender's age. Poor comprehenders selected by the different methods were found to vary in IQ, working memory, but not attention. The findings show that differences across studies in tests and selection criteria used to define poor comprehension are not insignificant and can have substantial consequences for what is meant by poor comprehension and its associated deficits.

Difficulties with chronopsychology studies include a masking effect of variables, the combination of different rhythms and variations of strategies. An experiment is conducted to analyze the role of circadian variations of elementary processes in the variations of performance for a complex task. Twenty-four subjects solved anagrams and tried to find the rule of anagram construction, during two sessions, at 10 am and 5 pm. Responses were classified in three groups: (a) discovery of the anagram construction rule (R2 responses); (b) resolution of anagram without discovery of rule (R1 responses); (c) failure, no resolution of anagram (R0 responses). During the second session, R2 performances were better at 10 am than at 5 pm. In contrast, R1 performances were better at 5 pm than at 10 am. Rule application was faster at 10 am than at 5 pm. Results are discussed in terms of variations of short-term memory capacity (Folkard and Monk, 1980). Using chronopsychology to analyze the role of elementary processes in a complex task is discussed.

Preschoolers' number related skills and maternal guidance used to introduce and foster the acquisition of these skills were examined in 193 48-month-olds. Mother-child collaboration was observed during two number-related tasks: a dot-to-dot drawing task and a matching number representations task. Patterns of responsibility sharing in task resolution were coded from videos, using a cross-classification strategy adapted from Parent (2000). Using mother-child interactions as a means to assess early numeracy skills, we replicated past findings obtained when child numeracy skills were assessed autonomously (Baroody & Dowker, 2003; Sinclair, 1988). Results also indicate that mothers adjust their support and the demands of the task to meet their child's skill level. In addition, promoting an enjoyable affective climate and fostering child motivation to complete the task appeared to be a predominant aspect of maternal guidance. Together, these results support the relevance of evaluating children's numeracy skills in a social context and emphasize the importance of taking into account affective dimensions of mother-child interactions when evaluating the development of new cognitive skills.