Beatrice Dalla Barba

Inhibition of return in newborns is temporo-nasal asymmetrical

Abstract Inhibition of return (IOR) is a reduced tendency to orient toward a previously attended spatial location. Inhibition of return is caused by suddenly introduced visual cues and reflects an attentional bias toward novel locations. It is indexed by an increased latency and/or a reduced tendency of an eye movement to the inhibited location. Under monocular viewing conditions, we submitted 24 newborns (M age = 50 hours) to trials consisting of a pretest phase (a single visual cue shown at 15° from fixation) and a test phase (two simultaneous, identical stimuli shown in the two visual hemifields at 15°). The results showed that, in the test phase, eye movements occured more often and with a shorter latency toward the side that had not been cued in the pretest phase. It was also found that the bias against the cued hemifield (i.e., IOR) was greater in the temporal than in the nasal hemifield. It was concluded that IOR is present just after birth and is mediated by extrageniculate rather than geniculostriate pathways.

Locomotor strategies preceding independent walking: prospective study of neurological and language development in 424 cases.

Locomotor strategies used before the acquisition of independent walking were studied in 424 infants. 270 were survivors of neonatal intensive care (the index group); the other 154 (controls) had had no perintal complications. Five forms of locomotion were distinguished: crawling on hands and knees, creeping on the stomach, bottom‐shuffling, other, and none before independent walking. Crawling was the most common form of locomotion in both groups. A higher percentage in the index group were late crawlers (> 10 months), but similar proportions in both groups were bottom‐shufflers or simply stood up and walked. One of the most important factors influencing locomotor strategies was asymmetry. Analysis of the influence of locomotor strategies on psychomotor and linguistic outcome up to five years showed no significant relationships within the index group. However, within the control group, infants who crawled had a statistically greater incidence of later motor delay, which is in contrast to the findings of other studies

A mental number line in human newborns

In the 19th century Francis Galton first reported that humans represent numbers on a mental number line with smaller numbers on the left and larger numbers on the right. It has been suggested that this orientation emerges as a result of reading/writing habits for both words or numbers. Recent evidence in animals and infants in the first months of life has challenged the primary role of language in determining the left-to-right direction of spatial-numerical association, SNA. However, the possibility that SNA is learnt by early exposure to caregivers’ directional biases is still open. Here we show that 55-hour-old newborns, once habituated to a number (i.e., 12), spontaneously associated a smaller number (i.e., 4) with the left side and a larger number (i.e., 36) with the right side of space. Moreover, SNA in neonates was not absolute but relative. The same number (i.e., 12) was associated with the left side whenever the previously experienced number was larger (i.e., 36), but with the right side whenever the number was smaller (i.e., 4). Control on continuous physical variables showed that the effect was specific of discrete magnitudes. Hence, soon after birth humans associate smaller numbers with the left space and larger numbers with the right space. These results constitute strong evidence that in our species SNA originates from pre-linguistic and biologically precursors in the brain. SIGNIFICANCE STATEMENT For human adults, the representation of number and space is profoundly intertwined. Humans represent numbers on a left to right oriented Mental Number Line (MNL), with small numbers located on the left and larger ones on the right. How do these connections arise? Do we learn to associate numbers with space throughout cultural learning and social interactions or is this association rooted in the biology of the human brain? We showed that neonates spontaneously associate numbers with space. After being habituated to a certain number, neonates associated a smaller number with the left and a larger number with the right side. This evidence demonstrates that a predisposition to map numbers onto space is rooted in human neural systems.