Perception of opposite-moving dots in 3- to 5-month-old infants

Developmental changes in visual-cognitive and attentional functions in infancy

BACKGROUND

Identifying developmental changes in visual-cognitive and attentional functions during infancy may lead to early diagnosis of neurodevelopmental disorders such as ASD and ADHD.

AIMS

To clarify the developmental changes in visual-cognitive and attentional functions during infancy (3-36 months of age).

STUDY DESIGN

Cross-sectional study.

SUBJECTS

We included 23, 24, 31, and 26 participants aged 3, 9, 18, and 36 months, respectively (full-term births). Fifteen children who cried intensely or whose data could not be accurately recorded were excluded.

OUTCOME MEASURES

Three activities were given to each child while they were seated in front of a gaze-tracking device to evaluate re-gaze, motion transparency, and color-motion integration. We analyzed whether the child's attention shifted to the new stimulus in their peripheral vision in the re-gaze task. In the motion transparency and color-motion integration tasks, two images were presented simultaneously on the screen. In the motion transparency task, participants preferred random dots moving in opposite directions; in the color-motion task, they preferred subjective contours from apparent motion stimuli consisting of random red and green dots with different luminance.

RESULTS

In the re-gaze task, fewer 3-month-olds gazed at the new target than other age groups participants. All ages showed preference for target stimuli in the motion transparency task, but 3-month-olds showed significantly lower preference in the color-motion integration task.

CONCLUSION

These tasks may be useful for measuring visual-cognitive and attentional functions in infants.

Infants see illusory motion in static figures

We investigated illusory motion perception in 6-to-8-month-old infants using a static figure which produces strong illusory motion. In experiment 1 we prepared a control figure, which was physically similar to the illusory motion figure but which did not produce illusory motion. We presented the illusory figure and the control figure side-by-side, and measured infants' looking time at the target illusory figure. Results showed that the infants' looking time at the illusory figure was significantly longer than that for the control. In experiment 2 we made another set of stimuli consisting of the same local pattern used in experiment 1, but which did not produce illusory motion. The results showed that no preferences were observed in experiment 2. These results suggest that 6-to-8-month-old infants perceive illusory motion in static figures.

Fast development of global motion processing in human infants

Although global motion processing is thought to emerge early in infancy, there is debate regarding the age at which it matures to an adult-like level. In the current study, we address the possibility that the apparent age-related improvement in global motion processing might be secondary to age-related increases in the sensitivity of mechanisms (i.e., local motion detectors) that provide input to global motion mechanisms. To address this, we measured global motion processing by obtaining motion coherence thresholds using stimuli that were equally detectable in terms of contrast across all individuals and ages (3-, 4-, 5-, 6-, and 7-month-olds and adults). For infants, we employed a directional eye movement (DEM) technique. For adults, we employed both DEM and a self-report method. First, contrast sensitivity was obtained for a local task, using a stochastic motion display in which all the dots moved coherently. Contrast sensitivity increased significantly between 3 and 7 months, and between infancy and adulthood. Each subject was then tested on the global motion task with the contrast of the dots set to 2.5 × each individual's contrast threshold. Coherence thresholds were obtained by varying the percentage of coherently moving "signal" versus "noise" dots in the stochastic motion display. Results revealed remarkably stable global motion sensitivity between 3 and 7 months of age, as well as between infancy and adulthood. These results suggest that the mechanisms underlying global motion processing develop to an adult-like state very quickly.