Infant visual acuity as a function of viewing distance.

Dynamic retinoscopy has suggested that near vision may be more acute than far vision during early infancy. To test this, acuity thresholds were determined by presenting square wave gratings in a preference paradigm to 1- and 2-month-old human infants at 4 viewing distances. Gratings were paired with unpatterned fields; direction of first fixation was the dependent measure. Infants exhibited the same acuity at each of the distances at which gratings were presented. The results were interpreted as compatible with the fact that considerable optical defocusing does not seriously affect a visual system, such as the infant's, that is sensitive only to low spatial frequencies.     

Radial localization of odors by human newborns.

To study sensitivity to radial location of an odor source, 20 human newborns, ranging from 16 to 130 hours of age, were presented with a small amount of ammonium hydroxide. The odor source was placed near the nose slightly to the left or right of midline, with its position randomized over repeated trails. Direction of headturn with respect to the odor location and diffuse motor activity were scored from the videotape recordings of the newborns' behavior. It was found that as a group, the newborns turned away from the odor source more frequently than they turned toward it. The tendency to turn away from the odor was stronger in infants who displayed less motor activity after the response. Newborns also exhibited a right bias in the direction of the head movements. It is concluded that a spatially appropriate avoidance response is present in the neonate and that the newborn is innately sensitive to the radial location of an odor.     

The relative efficacy of vestibular-proprioceptive stimulation and the upright position in enhancing visual pursuit in neonates.

48 healthy neonates born to multiparae were randomly assigned to view a moving stimulus either in the horizontal or the upright position, with or without added vestibular stimulation and with or without pacifier sucking. The infant was shown a moving black line inside a strictly controlled visual environment provided by an apparatus which permitted horizontal and upright positioning and displacement of the infant. Visual tracking was recorded by a concealed TV camera positioned at a constant distance and angle from the infants' eyes in both positions. Quality of tracking during each of 4 trials was scored on a 7-point scale. Results indicate that vestibularproprioceptive stimulation provided to the infant either horizontally or semivertically significantly enhanced his visual tracking, whereas the upright position did not. Pacifier sucking also improved his performace.     

Fact and fantasy in chemical analysis

Chemical analysis is now so precise and sophisticated a science that it is difficult to appreciate that scarcely a century ago its deficiencies were a cause for public scandal. This article reviews some of the main causes for complaint and how they were remedied.