The law of brevity in macaque vocal communication is not an artifact of analyzing mean call durations

Words follow the law of brevity, i.e. more frequent words tend to be shorter. From a statistical point of view, this qualitative definition of the law states that word length and word frequency are negatively correlated. Here the recent finding of patterning consistent with the law of brevity in Formosan macaque vocal communication (Semple et al., 2010) is revisited. It is shown that the negative correlation between mean duration and frequency of use in the vocalizations of Formosan macaques is not an artifact of the use of a mean duration for each call type instead of the customary 'word' length of studies of the law in human language. The key point demonstrated is that the total duration of calls of a particular type increases with the number of calls of that type. The finding of the law of brevity in the vocalizations of these macaques therefore defies a trivial explanation.Comment: Little improvements of the statistical argument

The parameters of Menzerath-Altmann law in genomes

The relationship between the size of the whole and the size of the parts in language and music is known to follow Menzerath-Altmann law at many levels of description (morphemes, words, sentences...). Qualitatively, the law states that larger the whole, the smaller its parts, e.g., the longer a word (in syllables) the shorter its syllables (in letters or phonemes). This patterning has also been found in genomes: the longer a genome (in chromosomes), the shorter its chromosomes (in base pairs). However, it has been argued recently that mean chromosome length is trivially a pure power function of chromosome number with an exponent of -1. The functional dependency between mean chromosome size and chromosome number in groups of organisms from three different kingdoms is studied. The fit of a pure power function yields exponents between -1.6 and 0.1. It is shown that an exponent of -1 is unlikely for fungi, gymnosperm plants, insects, reptiles, ray-finned fishes and amphibians. Even when the exponent is very close to -1, adding an exponential component is able to yield a better fit with regard to a pure power-law in plants, mammals, ray-finned fishes and amphibians. The parameters of Menzerath-Altmann law in genomes deviate significantly from a power law with a -1 exponent with the exception of birds and cartilaginous fishes.Comment: Typos and little inaccuracies corrected. Title and references updated (the previous update failed

The challenges of statistical patterns of language: the case of Menzerath's law in genomes

The importance of statistical patterns of language has been debated over decades. Although Zipf's law is perhaps the most popular case, recently, Menzerath's law has begun to be involved. Menzerath's law manifests in language, music and genomes as a tendency of the mean size of the parts to decrease as the number of parts increases in many situations. This statistical regularity emerges also in the context of genomes, for instance, as a tendency of species with more chromosomes to have a smaller mean chromosome size. It has been argued that the instantiation of this law in genomes is not indicative of any parallel between language and genomes because (a) the law is inevitable and (b) non-coding DNA dominates genomes. Here mathematical, statistical and conceptual challenges of these criticisms are discussed. Two major conclusions are drawn: the law is not inevitable and languages also have a correlate of non-coding DNA. However, the wide range of manifestations of the law in and outside genomes suggests that the striking similarities between non-coding DNA and certain linguistics units could be anecdotal for understanding the recurrence of that statistical law.Comment: Title changed, abstract and introduction improved and little corrections on the statistical argument

Compression as a universal principle of animal behavior

A key aim in biology and psychology is to identify fundamental principles underpinning the behavior of animals, including humans. Analyses of human language and the behavior of a range of non-human animal species have provided evidence for a common pattern underlying diverse behavioral phenomena: words follow Zipf's law of brevity (the tendency of more frequently used words to be shorter), and conformity to this general pattern has been seen in the behavior of a number of other animals. It has been argued that the presence of this law is a sign of efficient coding in the information theoretic sense. However, no strong direct connection has been demonstrated between the law and compression, the information theoretic principle of minimizing the expected length of a code. Here we show that minimizing the expected code length implies that the length of a word cannot increase as its frequency increases. Furthermore, we show that the mean code length or duration is significantly small in human language, and also in the behavior of other species in all cases where agreement with the law of brevity has been found. We argue that compression is a general principle of animal behavior, that reflects selection for efficiency of coding.Comment: This is the pre-proofed version. The published version will be available at http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291551-670

Mapa de la recerca del Campus de Vilanova i la Geltrú

Postprint (author’s final draft

When is Menzerath-Altmann law mathematically trivial? A new approach

Menzerath’s law, the tendency of Z (the mean size of the parts) to decrease as X (the number of parts) increases, is found in language, music and genomes. Recently, it has been argued that the presence of the law in genomes is an inevitable consequence of the fact that Z = Y/X, which would imply that Z scales with X as Z~1/X. That scaling is a very particular case of Menzerath-Altmann law that has been rejected by means of a correlation test between X and Y in genomes, being X the number of chromosomes of a species, Y its genome size in bases and Z the mean chromosome size. Here we review the statistical foundations of that test and consider three non-parametric tests based upon different correlation metrics and one parametric test to evaluate if Z~1/X in genomes. The most powerful test is a new non-parametric one based upon the correlation ratio, which is able to reject Z~1/X in nine out of 11 taxonomic groups and detect a borderline group. Rather than a fact, Z~1/X is a baseline that real genomes do not meet. The view of Menzerath-Altmann law as inevitable is seriously flawed.Peer ReviewedPostprint (author’s final draft

The Phylogeny and Function of Vocal Complexity in Geladas

The complexity of vocal communication varies widely across taxa – from humans who can create an infinite repertoire of sound combinations to some non-human species that produce only a few discrete sounds. A growing body of research is aimed at understanding the origins of ‘vocal complexity’. And yet, we still understand little about the evolutionary processes that led to, and the selective advantages of engaging in, complex vocal behaviors. I contribute to this body of research by examining the phylogeny and function of vocal complexity in wild geladas (Theropithecus gelada), a primate known for its capacity to combine a suite of discrete sound types into varied sequences. First, I investigate the phylogeny of vocal complexity by comparing gelada vocal communication with that of their close baboon relatives and with humans. Comparisons of vocal repertoires reveal that geladas – specifically the males – produce a suite of unique or ‘derived’ call types that results in a more diversified vocal repertoire than baboons. Also, comparisons of acoustic properties reveal that geladas produce vocalizations with greater spectro-temporal modulation, a feature shared with human speech, than baboons. Additionally, I show that the same organizational principle – Menzerath’s law – underpins the structure of gelada vocal sequences (i.e., combinations of derived and homologous call types) and human sentences. Second, I investigate the function of vocal complexity by examining the perception of male complex vocal sequences (i.e., those with more derived call types), the contexts in which they are produced, and how their production differs across individuals. A playback experiment shows that female geladas perceive ‘complex’ and ‘simple’ vocal sequences as being different. Then, two observational studies show that male production of complex vocal sequences mediates their affiliative interactions with females, both during neutral periods and periods of uncertainty (e.g., following conflicts). Finally, I find evidence that vocal complexity can act as a signal of male ‘quality’, in that more dominant males exhibit higher levels of vocal complexity than their subordinate counterparts. Collectively, the work presented in this dissertation presents an integrative investigation of the ultimate origins of complex communication systems, and in the process, it highlights the critical importance of approaching the study of complexity from several scientific perspectives.PHDPsychologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/138479/1/gustison_1.pd