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Updated: Jun 27, 2026
Infant Auditory Processing and Event-related Brain Oscillations
Published on: July 1, 2015
Induced alpha-band oscillations reflect ratio-dependent number discrimination in the infant brain
Melissa E Libertus1, Laura B Pruitt, Marty G Woldorff
1Center for Cognitive Neuroscience, Levine Science Research Center, Duke University, Durham, NC 27708, USA. melissa.libertus@duke.edu
Insights
Infant brains detect numerical novelty, showing number discrimination is ratio-dependent. This finding suggests early cognitive abilities follow Weber's Law, similar to adults.
Area of Science:
- Cognitive Neuroscience
- Developmental Psychology
- Neuroscience
Background:
- Infants can discriminate numbers, but evidence for ratio-dependence is limited by behavioral measures.
- Adults and animals show ratio-dependent number discrimination adhering to Weber's Law.
- Previous research lacked neural evidence for infant ratio-dependent numerical discrimination.
Purpose of the Study:
- To investigate whether 7-month-old infants exhibit ratio-dependent numerical discrimination.
- To provide neural evidence for the continuity of number discrimination abilities from infancy to adulthood.
- To explore the brain activity associated with detecting numerical novelty in infants.
Main Methods:
- Presented 7-month-old infants with familiar and novel numerosities.
- Recorded electroencephalogram (EEG) measures of brain activity during numerical tasks.
- Analyzed alpha-band and theta-band oscillations for differences between familiar and novel numbers.
Main Results:
- Infant brains detected numerical novelty, with distinct alpha and theta band oscillations.
- Alpha-band spectral power, particularly over midline and right posterior sites, was modulated by the ratio of familiar to novel numerosities.
- These findings indicate that numerical discrimination in infancy is ratio-dependent.
Conclusions:
- Neural evidence confirms ratio-dependent numerical discrimination in 7-month-old infants, following Weber's Law.
- This suggests continuity in numerical cognition across human development.
- Frontoparietal cortical networks likely support early ratio-dependent number discrimination, aligning with findings in older individuals.
Abstract:
Behavioral studies show that infants are capable of discriminating the number of objects or events in their environment, while also suggesting that number discrimination in infancy may be ratio-dependent. However, due to limitations of the dependent measures used with infant behavioral studies, the evidence for ratio dependence falls short of the vast psychophysical datasets that have established ratio dependence, and thus, adherence to Weber's Law in adults and nonhuman animals. We addressed this issue in two experiments that presented 7-month-old infants with familiar and novel numerosities while electroencephalogram measures of their brain activity were recorded. These data provide convergent evidence that the brains of 7-month-old infants detected numerical novelty. Alpha-band and theta-band oscillations both differed for novel and familiar numerical values. Most importantly, spectral power in the alpha band over midline and right posterior scalp sites was modulated by the ratio between the familiar and novel numerosities. Our findings provide neural evidence that numerical discrimination in infancy is ratio dependent and follows Weber's Law, thus indicating continuity of these cognitive processes over development. Results are also consistent with the idea that networks in the frontal and parietal cortices support ratio-dependent number discrimination in the first year of human life, consistent with what has been reported in neuroimaging studies in adults and older children.
