Robert L. Freedland

The detection of slow stimulus movement in 2- to 5-month-olds

Preferences for moving over static bars were assessed in 8-, 16-, and 20-week-old human infants. The display consisted of two adjacent horizontal bars one of which moved with one of four velocities (0.70, 1.4, 2.8 or 5.6 degrees/s) through one of four distances (11, 22, 44, or 88 arcmin) before reversing and traveling in the other direction at the same velocity. No significant preferences for motion were obtained at 8 weeks. At both 16 and 20 weeks of age, however, preferences for motion were determined exclusively by the velocity of the movement and were unaffected by the excursion of the bar. The minimum velocities that elicited significant preferences for motion were 5.08 degrees/s and 2.32 degrees/s at 16 and 20 weeks of age, respectively. The more attentive 20-week-olds, however, showed significant preferences for motion above a velocity of approximately 1.8 degrees/s. The addition of static reference bars had little influence on these preferences for motion in 20-week-olds; preferences were again related exclusively to the velocity of the bars movement. The results are discussed in terms of the development of motion-sensitive mechanisms within the visual system.

Detection of Relative Motion by Human Infants.

Two experiments were conducted on the detection of relative motion by 8- and 20-week-old infants.

A Large Scale Study of the Psychometric Characteristics of the IBR Modified Overt Aggression Scale: Findings and Evidence for Increased Self-Destructive Behaviors in Adult Females with Autism Spectrum Disorder

The psychometric characteristics of the IBR Modified Overt Aggression Scale were studied in over 2,000 people with Intellectual Disability (ID). Reliability ranged from good to excellent. Aggression toward others and objects was highest in the youngest adults, in those in the moderate to severe range of ID, and in those with an autism spectrum diagnosis. Self-injury was highest in those in the severe to profound range of ID and in those with autism, particularly the females. Females with autism were also more likely to make the most self-deprecating statements. Our data suggest that adult females with autism are a unique group and support the notion that mood and anxiety disorders play a role in self-destructive behaviors in this population.

Detection of stimulus motion in 5-month-old infants.

Five-month-old infants were tested by the method of preferential looking for discrimination between a pattern undergoing oscillating apparent motion and an identical static pattern. Sensitivity to small spatial displacements was evident at temporal frequencies of 8 and 16 Hz. Preference for the moving display was related independently to the temporal frequency of oscillation and the magnitude of the spatial displacement. Preferences for the moving display increased asymptotically across spatial displacements from 11 to 89 arc min. Preferences peaked between temporal oscillation frequencies of 8 and 16 Hz. Preference was not related to the ratio of these two variables--velocity. The minimum displacement threshold of 7.36 arc min was found to depend on the size of the elements in the pattern and on the temporal frequency of oscillation. The results demonstrate that motion-sensitive mechanisms responsive to small spatial displacements are present at 5 months of age.

Speed discrimination in 20-week-old infants☆

Abstract Discrimination of the speeds of two adjacent moving bars was studied in 20-week-old infants. Speeds ranging from 2 to 10°/s were used. Logistic regression was used to predict the side of the screen with the faster moving bar given the multiple observed dependent variables on each trial. Group psychometric functions showed approximate Weber fractions for speed discrimination near .35 at 3.3°/s and .67 at 10.0°/s. The results provide psychophysical evidence for speed discrimination by 20-week-olds and are discussed in terms of their implications for various visuomotor functions.

Quantifying established clinical assessment measures using 3D-movement analysis in individuals with Down syndrome.

Purpose. A movement protocol for quantifying functional limitation in people with Down syndrome (DS) during the execution of a series of range of motion (ROM) tasks has been developed as a new assessment approach, combining quantitative measures of movement analysis and functional mobility with clinically established qualitative motor skill assessments. Methods. Fifteen subjects with DS and 11 subjects with typical development were evaluated using this movement protocol. Results. The results revealed longer durations in execution across all tasks in the DS group and were most likely due to low muscular tone and poor coordination. A significant difference in ankle ROM was found in the DS group during leg-lifting, with a wide plantar-flexion demonstrated during the entire movement. This result may be associated with the typical strategy for foot contact that generally favours the toe. Significant differences were also found in the trunk ROM and in the knee ROM and may likely reflect an increase of agonist–antagonist co-contraction, a strategy that may modify stability and dynamic equilibrium. Conclusion. The combined quantitative/qualitative protocol is an important advancement in evaluating individuals with DS and should be integrated into a more comprehensive evaluation of dynamic gait and lower limb analysis.

Nonlinear pattern vision processes in early infancy

Abstract This study explored a possible nonlinear process in the pattern vision of 1 1 2 - to 3-month-old human infants by using a herringbone pattern. Adults perceive a global orientation in this pattern from the arrangement of local line segments oriented at right angles to each other. Fourier analysis of this pattern, however, shows no power at the perceived global orientation. In essence, no linear filtering of this pattern will yield energy in the perceived global orientation of the herringbone pattern. Infant perceptual theories based on the linear systems approach would predict that infants should be insensitive to this global orientation of the herringbone. Results of a preference procedure in Experiment 1 showed that 12-week-olds preferred the globally vertical and horizontal herringbones over the oblique herringbones. This preference is not predicted by linear systems accounts of pattern preferences. Experiment 2 provided converging evidence for nonlinear pattern vision processes at 12 weeks of age using a habituation procedure. Taken together, these results indicate that nonlinear pattern vision processes are functional by 3 months of age in the human visual system.