Processing order in short-term memory is spatially biased in children.

Area of Science:

• Cognitive Psychology
• Developmental Psychology
• Neuroscience

Background:

• Adults commonly map sequential information onto a mental horizontal line, aligning with their reading and writing system's directionality (e.g., left-to-right in Western cultures).
• Previous research has explored the cultural versus innate determinants of this spatial bias, but further investigation is needed, particularly in developmental populations.

Purpose of the Study:

• To investigate the development of the spatial-ordinal association, specifically the left-to-right bias in processing serial information, across different age groups.
• To determine at what age this bias, commonly observed in adults, begins to emerge in children.

Main Methods:

• A rotation task involving unlabeled serial information was employed across four experiments.
• Participants included children from toddler age (2 years) to grade 5 (12 years), and adults.
• Experiments systematically controlled for potential confounds and adjusted task explicitness and mental rotation.

Main Results:

• A clear left-to-right bias was not consistently observed in younger children across initial experiments.
• A global left-to-right bias was finally detected across age groups in Experiment 4, particularly in 2nd to 4th graders (7-9 years old) and adults.
• A weaker bias was noted in younger children, suggesting a potential emergence in preschool years (around 4 years old).

Conclusions:

• Spatial-ordinal associations, like the left-to-right bias, are present in children as early as primary school, mirroring adult patterns.
• The strength of this bias appears to increase with age and literacy expertise, indicating a developmental trajectory.
• The findings suggest that while the bias may begin to emerge in preschool, it is significantly reinforced through literacy acquisition.