No intrinsic number bias: Evaluating the role of perceptual discriminability in magnitude categorization

Accumulating evidence suggests that there is a spontaneous preference for numerical, compared to non-numerical (e.g., cumulative surface area), information. However, given a paucity of research on the perception of non-numerical magnitudes, it is unclear whether this preference reflects a specific bias towards number, or a general bias towards the more perceptually discriminable dimension (i.e., number). Here, we found that when the number and area of visual dot displays were matched in mathematical ratio, number was more perceptually discriminable than area in both adults and children. Moreover, both adults and children preferentially categorized these ratio-matched stimuli based on number, consistent with previous work. However, when number and area were matched in perceptual discriminability, a different pattern of results emerged. In particular, children preferentially categorized stimuli based on area, suggesting that children's previously observed number bias may be due to a mismatch in the perceptual discriminability of number and area, not an intrinsic salience of number. Interestingly, adults continued to categorize the displays on the basis of number. Altogether, these findings suggest a dominant role for area during childhood, refuting the claim that number is inherently and uniquely salient. Yet they also reveal an increased salience of number that emerges over development. Potential explanations for this developmental shift are discussed.

Research Highlights

• Previous work found that children and adults spontaneously categorized dot array stimuli by number, over other magnitudes (e.g., area), suggesting number is uniquely salient.
• However, here we found that when number and area were matched by ratio, as in prior work, number was significantly more perceptually discriminable than area.
• When number and area were made equally discriminable (‘perceptually-matched’), children, contra adults, spontaneously categorized stimuli by area over number (and other non-numerical magnitudes).
• These findings suggest that area may be uniquely salient early in childhood, with the previously-observed number bias not emerging until later in development.

     

Early lexical development of children raised in institutional care in Russia

Children abandoned to institutions display a host of developmental delays, including those involving general cognition and language. The majority of published studies focus on children over 3 years of age; little is known about whether these delays may be detected earlier when children undergo rapid lexical development. To investigate the early language development of children raised in institutional settings in the Russian Federation, we compared a group of children in institutional care (n = 36; 8–35 months) to their age-matched peers raised in biological families, who have never been institutionalized (n = 72) using the Russian version of the CDI. The results suggest that institutionalization is associated with pronounced delays in children's early language development with large and robust effect sizes. Among children with a history of institutionalization, these delays are also associated with difficulties in Daily Living skills, communication, and socialization.