Numbers in Action

Humans show a remarkable tendency to describe and think of numbers as being placed on a mental number line (MNL), with smaller numbers located on the left and larger ones on the right. Faster responses to small numbers are indeed performed on the left side of space, while responses to large numbers are facilitated on the right side of space (spatial-numerical association of response codes, SNARC effect). This phenomenon is considered the experimental demonstration of the MNL and has been extensively replicated throughout a variety of paradigms. Nevertheless, the majority of previous literature has mainly investigated this effect by means of response times and accuracy, whereas studies considering more subtle and automatic measures such as kinematic parameters are rare (e.g., in a reaching-to-grasp movement, the grip aperture is enlarged in responding to larger numbers than in responding to small numbers). In this brief review we suggest that numerical magnitude can also affect the what and how of action execution (i.e., temporal and spatial components of movement). This evidence could have large implications in the strongly debated issue concerning the effect of experience and culture on the orientation of MNL

Numerical Abilities in Nonhumans: The Perspective of Comparative Studies

The history of the study of animal numerical cognition is characterized by an unfortunate start: the Clever Hans story, which caused a widespread skepticism across the scientific community. In the last decades, a growing body of evidence demonstrates numerical skills in nonhumans; nonetheless, studies have focused on adult subjects. Here, it will be discussed numerical comprehension in day-old chicks, a model species that allows an insight on the early development of cognitive abilities. Newborn chicks discriminate between diverse numbers, solve arithmetic calculations, and use ordinal information. This animal model allowed to also unveil another peculiar aspect of numbers: their association with space. This ordered representation of numbers in space is known in humans as the mental number line (MNL) and refers to an ascending mapping of numbers from left to right. Chicks associate smaller numbers with the left and larger numbers with the right space. The paradigm used to test spatial numerical association (SNA) in chicks has been proficiently used to also assess this association in human newborns, providing a suggestive example of animal research inspiring developmental studies. Overall findings from 1- or few-day-old chicks, virtually na\uefve or reared under strictly controlled conditions, constitute a strong case for the claim that numbers are a primitive and inherent information processed by animals

Approach direction and accuracy, but not response times, show spatial-numerical association in chicks

open2noChicks trained to identify a target item in a sagittally-oriented series of identical items show a higher accuracy for the target on the left, rather than that on the right, at test when the series was rotated by 90˚. Such bias seems to be due to a right hemispheric dominance in visuospatial tasks. Up to now, the bias was highlighted by looking at accuracy, the measure mostly used in non-human studies to detect spatial numerical association, SNA. In the present study, processing by each hemisphere was assessed by scoring three variables: accuracy, response times and direction of approach. Domestic chicks were tested under monocular vision conditions, as in the avian brain input to each eye is mostly processed by the contralateral hemisphere. Four-day-old chicks learnt to peck at the 4th element in a sagittal series of 10 identical elements. At test, when facing a series oriented fronto-parallel, birds confined their responses to the visible hemifield, with high accuracy for the 4th element. The first element in the series was also highly selected, suggesting an anchoring strategy to start the proto-counting at one end of the series. In the left monocular condition, chicks approached the series starting from the left, and in the right monocular condition, they started from the right. Both hemispheres appear to exploit the same strategy, scanning the series from the most lateral element in the clear hemifield. Remarkably, there was no effect in the response times: equal latency was scored for correct or incorrect and for left vs. right responses. Overall, these data indicate that the measures implying a direction of choice, accuracy and direction of approach, and not velocity, i.e., response times, can highlight SNA in this paradigm. We discuss the relevance of the selected measures to unveil SNA.openRugani, Rosa; Regolin, LuciaRugani, Rosa; Regolin, Luci

Summation of Large Numerousness by Newborn Chicks

Newly hatched domestic chicks, reared with identical objects, when presented with sets of 3 vs. 2 objects disappearing one-by-one behind separate screens, spontaneously inspected the screen occluding the larger set; even when the continuous variables (area or perimeter) were controlled for (Rugani et al., 2009). Here, using a similar paradigm, we investigated the ability of chicks to perform addition on larger sets of objects. Chicks imprinted on five identical objects, were presented at test with 6 vs. 9 objects which disappeared one-by-one (Exp. 1). In Exp. 2, the same overall number of objects (15) was used, but employing an increased ratio, i.e., 5 vs. 10. In both experiments, when continuous variables were not made equal, chicks spontaneously inspected the screen occluding the larger set. However, when the size of the objects was adjusted so as to make the total surface area or perimeter equal for the two sets, chicks did not exhibit any preference. Lack of choice in the control conditions could be due to a combination of preferences; to rejoin the larger numerousness as well as the bigger objects (Rugani et al., 2010a). In Exp. 3, chicks were familiarized, during imprinting, with objects of various dimensions, in an attempt to reduce or suppress their tendency to approach objects larger than the familiar ones. Again chicks failed to choose at test between 5 vs. 10 objects when continuous variables were made equal. Results showed that chicks, after a one-by-one presentation of a large number of objects, rejoined the larger set. In order to choose the larger set, chicks estimated the objects in the two sets and then compared the outcomes. However, differently to what has been described for small numerousness, chicks succeeded only if non-numerical cues as well as numerical cues were available. This study suggests that continuous variables are computed by chicks for sets of objects that are not present at the same time and that are no longer visible at the time of choice

Effects of animacy on the processing of morphological Number: a cognitive inheritance?

Language encodes into morphology part of the information present in the referential world. Some features are marked in the great majority of languages, such as the numerosity of the referents that is encoded in morphological Number. Other features do not surface as frequently in morphological markings, yet they are pervasive in natural languages. This is the case of animacy, that can ground Gender systems as well as constrain the surfacing of Number. The diffusion of numerosity and animacy could mirror their biological salience at the extra-linguistic cognitive level. Human extra-linguistic numerical abilities are phylogenetically ancient and are observed in non-human animal species, especially when counting salient animate entities such as social companions. Does the saliency of animacy influence the morphological encoding of Number in language processing? We designed an experiment to test the encoding of morphological Number in language processing in relation to animacy. In Italian, Gender and Number are mandatorily expressed in a fusional morpheme. In some nouns denoting animate referents, Gender encodes the sex of referents and is semantically interpretable. In some other animate nouns and in inanimate nouns, Gender is uninterpretable at the semantic level. We found that it is easier to inflect for Number nouns when the inflectional morpheme is interpretable with respect to a semantic feature related to animacy. We discuss the possibility that the primacy of animacy in counting is mirrored in morphological processing and that morphology is designed to easily express information that is salient from a cognitive point of view

Is it only humans that count from left to right?

We report that adult nutcrackers (Nucifraga columbiana) and newborn domestic chicks (Gallus gallus) show a leftward bias when required to locate an object in a series of identical ones on the basis of its ordinal position. Birds were trained to peck at either the fourth or sixth element in a series of 16 identical and aligned positions. These were placed in front of the bird, sagittally with respect to its starting position. When, at test, the series was rotated by 90° lying frontoparallel to the bird's starting position, both species showed a bias for identifying selectively the correct position from the left but not from the right end. The similarity with the well-known phenomenon of the left-to-right spatially oriented number line in humans is considered

Linking land use inventories to biodiversity impact assessment methods

There is generally a mismatch in the land use classification of life cycle inventory (LCI) databases and life cycle impact assessment (LCIA) methods. This mismatch can hinder the proper assessment of land use impacts on biodiversity. To facilitate such assessments, we matched the land use classes of two global LCIA methods to five widely used LCI databases, one LCI nomenclature, and one multi-regional input-output database. In unclear cases, we assumed the worst case. Assumptions were especially necessary for unspecified land use intensity classes. We conclude with recommendations for LCI database and LCIA method developers.Industrial Ecolog

A research perspective towards a more complete biodiversity footprint: a report from the World Biodiversity Forum

ISSN:0948-3349ISSN:1614-750