Subitizing is a fast and accurate enumeration process of small sets of usually less than four objects. Several models were proposed in the literature. Critically, only pattern recognition theory suggests that subitizing performance is sensitive to the arrangement of the array. In our study, arrays of dots in random or canonical arrangements were enumerated. The subitizing range was larger and the reaction time slope was less steep in the canonical arrangements. When noise was added to the canonical pattern, the reaction time slope was proportional to the amount of noise. Moreover, arrangement has a stronger effect on sets with more than four objects. These results support the pattern recognition model of subitizing.

Number notations can influence the way numbers are handled in computations; however, the role of notation itself in mental processing has not been examined directly. From a mathematical point of view, it is believed that place-value number notation systems, such as the Indo-Arabic numbers, are superior to sign-value systems, such as the Roman numbers. However, sign-value notation might have sufficient efficiency; for example, sign-value notations were common in flourishing cultures, such as in ancient Egypt. Herein we compared artificial sign-value and place-value notations in simple numerical tasks. We found that, contrary to the dominant view, sign-value notation can be applied more easily than place-value notation for multi-power comparison and addition tasks. Our results are consistent with the popularity of sign-value notations that prevailed for centuries. To explain the notation effect, we propose a natural multi-power number representation based on the numerical representation of objects.

How do infants acquire the meaning of abstract words expressing negation? ‘No’ is among the first uttered words and emerges around the age of one, nevertheless, it is a subject of intense debate when and how exactly infants start interpreting utterances containing negation. According to one hypothesis, early in development, the comprehension and the production of verbal negation is restricted to a narrow range of meanings, for example to non-existence (‘No cookies’), and only much later infants develop a broader understanding and can correctly interpret propositional denial (‘Not x’) that may map onto a fully-fledged negation concept. Alternatively, however, they may rely on an adult-like negation concept from early on, but some forms of negations may pose more mapping difficulties. Here we tested infants’ understanding of two syntactically and semantically different forms of negation, existential negation and propositional denial. We engaged 15- and 18-month-old infants in a search task where they had to find a toy in one out of two locations based on verbal utterances involving existential negation or propositional denial. In Experiments 1-3 we found a parallel development for these two kinds of negation. 18-month-olds successfully comprehended both, while 15-month-olds did not understand either forms of negation. In Experiment 4 we excluded the possibility that 15-month-olds’ poor performance is explained by task-related difficulties. The parallel performance of the two age groups in the tasks involving two types of negation suggests that different forms of negation may share common conceptual underpinnings already in early development.

Absence is a notion that is usually captured by language-related concepts like zero or negation. Whether nonlinguistic creatures encode similar thoughts is an open question, as everyday behavior marked by absence (of food, of social partners) can be explained solely by expecting presence somewhere else. We investigated 8-day-old chicks’ looking behavior in response to events violating expectations about the presence or absence of an object. We found different behavioral responses to violations of presence and absence, suggesting distinct underlying mechanisms. Importantly, chicks displayed an avian signature of novelty detection to violations of absence, namely a sex-dependent left-eye-bias. Follow-up experiments excluded accounts that would explain this bias by perceptual mismatch or by representing the object at different locations. These results suggest that the ability to spontaneously form representations about the absence of objects likely belongs to the initial cognitive repertoire of vertebrate species.

SummaryAbsence is a notion that is usually captured by language-related concepts like zero or negation. Whether non-linguistic creatures encode similar thoughts is an open question, as everyday behavior marked by absence (of food, of social partners) can be explained solely by expecting presence somewhere else. We investigated 8-day-old chicks’ looking behavior in response to events violating expectations about the presence or absence of an object. We found different behavioral responses to violations of presence and absence, suggesting distinct underlying mechanisms. Importantly, chicks displayed an avian signature of novelty detection to violations of absence, namely a sex-dependent left-eye-bias. Follow-up experiments excluded accounts that would explain this bias by perceptual mismatch or by representing the object at different locations. These results suggest that the ability to spontaneously form thoughts about the absence of objects likely belongs to the initial cognitive repertoire of vertebrate species.