Occlusion is hard: Comparing predictive reaching for visible and hidden objects in infants and adults

Developmental trajectories of picture-based object representations during the first year of life

Experience with an object's photograph changes 9-month-olds' preference for the referent object, confirming they can represent objects from pictures. However, picture-based representations appear weaker than object-based representations. The current study's first objective was to investigate age differences in object recognition memory after familiarization with objects' pictures. The second objective was to test whether age differences in object permanence sensitivity with picture-based representations match those found with object-based representations, whereby 7-month-olds search more for familiar hidden objects but 11-month-olds search more for novel ones. Six- and 11-month-olds were familiarized with an object's photo and tested on their representation of the real object by comparing their reaching for it versus a novel object. Objects were visible under conditions testing recognition memory and hidden under conditions testing object permanence. Like 9-month-olds, 6- and 11-month-olds preferred novelty with visible objects, showing early object recognition after picture familiarization, as well as developmental continuity. Unlike 9-month-olds, who switched to preferring familiarity with hidden objects, 6- and 11-month-olds switched to null preference. This pattern fails to match 7- and 11-month-olds' hidden-object preferences after familiarization with real objects, revealing discontinuity in sensitivity to object permanence after picture familiarization, and suggesting that picture-based representations are weaker than object-based ones.

Sound effects: Multimodal input helps infants find displaced objects

Before 9 months, infants use sound to retrieve a stationary object hidden by darkness but not one hidden by occlusion, suggesting auditory input is more salient in the absence of visual input. This article addresses how audiovisual input affects 10-month-olds' search for displaced objects. In AB tasks, infants who previously retrieved an object at A subsequently fail to find it after it is displaced to B, especially following a delay between hiding and retrieval. Experiment 1 manipulated auditory input by keeping the hidden object audible versus silent, and visual input by presenting the delay in the light versus dark. Infants succeeded more at B with audible than silent objects and, unexpectedly, more after delays in the light than dark. Experiment 2 presented both the delay and search phases in darkness. The unexpected light-dark difference disappeared. Across experiments, the presence of auditory input helped infants find displaced objects, whereas the absence of visual input did not. Sound might help by strengthening object representation, reducing memory load, or focusing attention. This work provides new evidence on when bimodal input aids object processing, corroborates claims that audiovisual processing improves over the first year of life, and contributes to multisensory approaches to studying cognition. Statement of contribution What is already known on this subject Before 9 months, infants use sound to retrieve a stationary object hidden by darkness but not one hidden by occlusion. This suggests they find auditory input more salient in the absence of visual input in simple search tasks. After 9 months, infants' object processing appears more sensitive to multimodal (e.g., audiovisual) input. What does this study add? This study tested how audiovisual input affects 10-month-olds' search for an object displaced in an AB task. Sound helped infants find displaced objects in both the presence and absence of visual input. Object processing becomes more sensitive to bimodal input as multisensory functions develop across the first year.