Children Use Statistics and Semantics in the Retreat from Overgeneralization

How do children learn to restrict their productivity and avoid ungrammatical utterances? The present study addresses this question by examining why some verbs are used with un- prefixation (e.g., unwrap) and others are not (e.g., *unsqueeze). Experiment 1 used a priming methodology to examine children's (3–4; 5–6) grammatical restrictions on verbal un- prefixation. To elicit production of un-prefixed verbs, test trials were preceded by a prime sentence, which described reversal actions with grammatical un- prefixed verbs (e.g., Marge folded her arms and then she unfolded them). Children then completed target sentences by describing cartoon reversal actions corresponding to (potentially) un- prefixed verbs. The younger age-group's production probability of verbs in un- form was negatively related to the frequency of the target verb in bare form (e.g., squeez/e/ed/es/ing), while the production probability of verbs in un- form for both age groups was negatively predicted by the frequency of synonyms to a verb's un- form (e.g., release/*unsqueeze). In Experiment 2, the same children rated the grammaticality of all verbs in un- form. The older age-group's grammaticality judgments were (a) positively predicted by the extent to which each verb was semantically consistent with a semantic “cryptotype” of meanings - where “cryptotype” refers to a covert category of overlapping, probabilistic meanings that are difficult to access - hypothesised to be shared by verbs which take un-, and (b) negatively predicted by the frequency of synonyms to a verb's un- form. Taken together, these experiments demonstrate that children as young as 4;0 employ pre-emption and entrenchment to restrict generalizations, and that use of a semantic cryptotype to guide judgments of overgeneralizations is also evident by age 6;0. Thus, even early developmental accounts of children's restriction of productivity must encompass a mechanism in which a verb's semantic and statistical properties interact

Leukocyte trafficking between stromal compartments:lessons from rheumatoid arthritis

The trafficking of leukocytes from their site of production in the bone marrow through the circulation and into peripheral tissues is a highly coordinated and tightly regulated process in healthy individuals. Lymphocytes are long-lived cells that visit many lymphoid and peripheral tissues over their lifetime and can even recirculate back to the bone marrow, whereas granulocytes and monocytes are not thought to recirculate so widely. Using rheumatoid arthritis (RA) as an example, this Review explores the migratory journey of leukocytes during the establishment and resolution of disease — from the blood, through the lymphoid tissues and into peripheral sites such as the lungs and the gut before their entry into the synovium. This Review explores our current understanding of differences in the molecular processes that regulate leukocyte trafficking at different phases of disease and in different stromal compartments, which could help to explain the disease heterogeneity seen in patients with RA. Expanding our knowledge of these processes will open new avenues in the clinical management of RA, paving the way for personalized medicine that is founded on the pathological molecular signature of each patient, which varies according to their phase of disease or disease subtype