Experimental Evidence From Newborn Chicks Enriches Our Knowledge on Human Spatial–Numerical Associations

Núñez and Fias raised concerns on whether our results demonstrate a linear number‐space mapping. Patro and Nuerk urge caution on the use of animal models to understand the origin (cultural vs. biological) of the orientation of spatial–numerical association. Here, we discuss why both objections are unfounded.     

Imprinted numbers: newborn chicks’ sensitivity to number vs. continuous extent of objects they have been reared with

Newborn chicks were tested for their sensitivity to number vs. continuous physical extent of artificial objects they had been reared with soon after hatching. Because of the imprinting process, such objects were treated by chicks as social companions. We found that when the objects were similar, chicks faced with choices between 1 vs. 2 or 2 vs. 3 objects chose the set of objects of larger numerosity, irrespective of the number of objects they had been reared with. Moreover, when volume, surface or contour length were controlled for using sets of 1 vs. 4, 1 vs. 6 or 1 vs. 3 objects, chicks resorted to choosing the larger object, rather than the familiar numerosity. When, however, chicks were reared with objects differing in their aspect (colour, size, and shape) and then tested with completely novel objects (of different colour and shape but controlled for continuous extent), they chose to associate with the same number of objects they had been reared with. These results suggest that identification of objects as different and separate individuals is crucial for the computation of number rather than continuous extent in numerical representation of small numerosities and provide a striking parallel with results obtained in human infants. Early availability of small numerosity discrimination by chicks strongly suggests that these abilities are in place at birth.     

Experience and geometry: controlled-rearing studies with chicks

Animals can reorient making use of the geometric shape of an environment, i.e., using sense and metric properties of surfaces. Animals reared soon after birth either in circular or in rectangular enclosures (and thus affording different experiences with metric properties of the spatial layout) showed similar abilities when tested for spatial reorientation in a rectangular enclosure. Thus, early experience in environments with different geometric characteristics does not seem to affect animals’ ability to reorient using sense and metric information. However, some results seem to suggest that when geometric and non-geometric information are set in conflict, rearing experience could affect the relative dominance of featural (landmark) and geometric information. In three separate experiments, newborn chicks reared either in circular- or in rectangular-shaped home-cages were tested for spatial reorientation in a rectangular enclosure, with featural information provided either by panels at the corners or by a blue-coloured wall. At test, when faced with affine transformations in the arrangement of featural information that contrasted with the geometric information, chicks showed no evidence of any effect of early experience on their relative use of geometric and featural information for spatial reorientation. These findings suggest that, at least for this highly precocial species, the ability to deal with geometry seems to depend more on predisposed mechanisms than on learning and experience after hatching.     

Training generalized spatial skills

Spatial transformation skills are an essential aspect of cognitive ability. These skills can be improved by practice, but such improvement has usually been specific to tasks and stimuli. The present study investigated whether intensive long-term practice leads to change that transcends stimulus and task parameters. Thirty-one participants (14 male, 17 female) were tested on three cognitive tasks: a computerized version of the Shepard-Metzler (1971) mental rotation task (MRT), a mental paper-folding task (MPFT), and a verbal analogies task (VAT). Each individual then participated in daily practice sessions with the MRT or the MPFT over 21 days. Postpractice comparisons revealed transfer of practice gains to novel stimuli for the practiced task, as well as transfer to the other, nonpracticed spatial task. Thus, practice effects were process based, not instance based. Improvement in the nonpracticed spatial task was greater than that in the VAT; thus, improvement was not merely due to greater ease with computerized testing.     

A case of partial biotinidase deficiency associated with autism.

We report the case of a child with partial biotinidase deficiency and autistic developmental disorder. We arrived at the diagnosis of biotinidase deficiency when the child was almost 4 years of age. Consequently, he began cofactor biotin treatment (10 mg daily) which did not resolve his autistic behavior. His younger brother was affected by partial biotinidase deficiency diagnosed at birth through our neonatal screening program. He was precociously treated with cofactor biotin therapy (10 mg daily) and did not show any behavioral abnormality or developmental delay. Since the brain is quite vulnerable to biotin deficiency, delayed biotin therapy could result in neurological damage. Our patient is the first case of partial biotinidase deficiency associated with autism. We hypothesize that the low biotinidase activity could have caused biotin deficiency in his brain and cerebrospinal fluids and consequently serious neurological problems, such as stereotyped and autistic behaviors, which were irreversible in spite of biotin supplementation.     

Short-term memory and verbal learning with auditory phonological coding defect: a neuropsychological case study.

A patient is described with a rarely reported linguistic syndrome: he could repeat words but not nonwords. The patient produced semantic paraphasias in repetition and could read both words and nonwords flawlessly. His basic difficulties were localized in auditory phonological coding, identifying a clinical picture called "phonemic deafness." Short-term memory and verbal learning results suggested that a standard, selective short-term memory defect can be induced by auditory phonological coding deficits as well as by "pure" short-term memory capacity limitation and other phonological deficits. Findings also provided evidence that lexical-semantic code can allow normal verbal learning.     

Immediate memory spans in dementia

Spatial span (Corsi's block-tapping test) and verbal spans for digits (Wechsler Digits Forward Test) and for words were measured in 30 normal subjects and in 51 demented patients, divided into two groups (mildly demented and severely demented) according to selective clinical and neuropsychological criteria. Statistical analysis showed significant differences among the three groups for spatial span. By contrast, controls' and mildly demented patients' performances on both verbal spans were not significantly different. These findings are discussed in the light of theory about working memory.     

Lateralized hand gesture during speech

A group of individuals conversing in natural dyads and a group of lecturers were observed for lateral hand movement patterns during speech. Right-handed individuals in both groups displayed a significant right hand bias for gesture movements but no lateral bias for self-touching movements. The study provides external validity for previous laboratory studies of lateralized hand gesture. The results were interpreted as evidence of a central processor for both spoken and gestural communication.