1 Menzerath’s Law

1.1 Durations and Intervals

The distribution of element durations and inter-onset intervals from the whale vocal sequences included in this analysis. The times are z-scored within each study to enable direct comparison.

Figure 1: The distribution of element durations and inter-onset intervals from the whale vocal sequences included in this analysis. The times are z-scored within each study to enable direct comparison.

To assess whether the strength of Menzerath’s law in human language is similar when computed from element durations and inter-onset intervals, I conducted a supplementary analysis with a corpus of spoken language data that was collected to study efficiency in information encoding (1). DoReCo could not be used for this supplementary analysis because it includes the short gaps between phonemes in its measurements (2), making it impossible to analyze element durations and inter-onset intervals separately without a reanalysis of the raw data. Coupe et al.’s dataset is composed of 2,288 recordings of speech, ranging from three to five sentences in length, and representing 17 different languages (1). For each recording, they collected the number of syllables, the overall duration including vocalizations and silence, and the duration only including silence, making it possible to compute the average element duration and inter-onset interval of each recording.

Each sequence in Coupe et al.’s data is a set of sentences from a single speaker (1). Analyzing Menzerath’s law in utterances above the sentence-level is unusual but has precedent (3, 4). It would be ideal to conduct this analysis at the same level of the linguistic hierarchy as DoReCo (e.g., phonemes within words, words within sentences.), but Coupe et al.’s dataset is the only one I found that separates phonation from silence (1).

For each sequence, I analyzed (1) the length in syllables, (2) the average duration of syllables, and (3) the average inter-onset interval between syllables. These data were analyzed using the same linear model as in the main text, excluding the varying intercept because each point corresponds to the average duration/interval within a sequence:

\[\begin{equation} \ln(\textrm{duration}) \sim \ln(\textrm{length}) \tag{1} \end{equation}\]

The results indicate that the strength of Menzerath’s law for syllables in series of sentences is quite similar when computed from element durations (estimate = -0.216, 95% CI: [-0.256, -0.176]) and inter-onset intervals (estimate = -0.292, 95% CI: [-0.331, -0.253]).

1.2 Effects in Whale Data

Table 1: The effect of sequence length on element durations and inter-onset intervals for each whale species, computed from the base model that excludes position. 2.5% and 97.5% denote the lower and upper bounds of the 95% confidence intervals.

Group

Species

Type

Effect

2.5%

97.5%

Mysticete

Blue Whale

Elements

-0.255

-0.331

-0.178

Bowhead Whale

Elements

-0.184

-0.318

-0.051

Common Minke Whale

Elements

-0.278

-0.294

-0.261

Humpback Whale

Intervals

-0.678

-0.692

-0.665

North Pacific Right Whale

Elements

0.309

0.278

0.340

Sei Whale

Elements

-0.194

-0.329

-0.059

Odontocete

Bottlenose Dolphin

Intervals

-0.242

-0.347

-0.138

Commerson's Dolphin

Intervals

0.221

0.087

0.356

Heaviside's Dolphin

Intervals

-0.119

-0.320

0.083

Hector's Dolphin

Intervals

-0.008

-0.274

0.258

Killer Whale

Elements

0.121

0.003

0.239

Narrow-Ridged Finless Porpoise

Intervals

-0.304

-0.338

-0.270

Peale's Dolphin

Intervals

-0.333

-0.489

-0.177

Risso's Dolphin

Intervals

-0.420

-0.448

-0.392

Sperm Whale

Intervals

-0.234

-0.241

-0.226

Table 2: The effect of sequence length and position on element durations and inter-onset intervals for each whale species, computed from the expanded model that includes both length and position. 2.5% and 97.5% denote the lower and upper bounds of the 95% confidence intervals.

Length

Position

Group

Species

Type

Effect

2.5%

97.5%

Effect

2.5%

97.5%

Mysticete

Blue Whale

Elements

-0.255

-0.331

-0.178

-0.064

-0.087

-0.041

Bowhead Whale

Elements

-0.179

-0.313

-0.046

-0.751

-0.789

-0.713

Common Minke Whale

Elements

-0.278

-0.294

-0.261

-0.017

-0.023

-0.011

Humpback Whale

Intervals

-0.678

-0.691

-0.665

-0.193

-0.201

-0.186

North Pacific Right Whale

Elements

0.309

0.278

0.340

0.107

0.096

0.119

Sei Whale

Elements

-0.194

-0.329

-0.058

-0.101

-0.132

-0.070

Odontocete

Bottlenose Dolphin

Intervals

-0.242

-0.346

-0.138

-0.084

-0.111

-0.056

Commerson's Dolphin

Intervals

0.221

0.087

0.356

-0.106

-0.118

-0.095

Heaviside's Dolphin

Intervals

-0.119

-0.320

0.083

0.019

0.010

0.027

Hector's Dolphin

Intervals

-0.008

-0.274

0.258

-0.001

-0.010

0.008

Killer Whale

Elements

0.121

0.021

0.221

0.528

0.428

0.628

Narrow-Ridged Finless Porpoise

Intervals

-0.305

-0.339

-0.271

0.168

0.151

0.185

Peale's Dolphin

Intervals

-0.333

-0.489

-0.177

-0.013

-0.017

-0.009

Risso's Dolphin

Intervals

-0.420

-0.448

-0.392

-0.196

-0.200

-0.192

Sperm Whale

Intervals

-0.234

-0.241

-0.226

0.028

0.026

0.031

1.3 Effects in Human Data

Table 3: The effect of sequence length on inter-onset intervals for each human language, computed from the base model that excludes position. 2.5% and 97.5% denote the lower and upper bounds of the 95% confidence intervals.

Language

Effect

2.5%

97.5%

Anal

-0.104

-0.113

-0.095

Arapaho

0.030

0.020

0.040

Asimjeeg Datooga

-0.063

-0.073

-0.053

Baïnounk Gubëeher

-0.102

-0.110

-0.093

Beja

-0.066

-0.073

-0.059

Bora

-0.127

-0.138

-0.116

Cabécar

-0.110

-0.120

-0.100

Cashinahua

-0.100

-0.108

-0.091

Daakie

-0.131

-0.141

-0.121

Dalabon

-0.079

-0.091

-0.066

Dolgan

-0.130

-0.139

-0.121

English (Southern England)

-0.053

-0.066

-0.040

Evenki

-0.101

-0.109

-0.092

Fanbyak

-0.091

-0.101

-0.080

French (Swiss)

-0.050

-0.063

-0.037

Goemai

-0.124

-0.138

-0.110

Gorwaa

-0.125

-0.136

-0.114

Hoocąk

-0.099

-0.109

-0.090

Jahai

-0.062

-0.073

-0.050

Jejuan

-0.093

-0.104

-0.083

Kakabe

-0.123

-0.135

-0.111

Kamas

-0.096

-0.111

-0.082

Komnzo

-0.081

-0.091

-0.071

Light Warlpiri

-0.144

-0.154

-0.133

Lower Sorbian

-0.078

-0.089

-0.067

Mojeño Trinitario

-0.147

-0.156

-0.137

Movima

-0.014

-0.023

-0.006

Nafsan (South Efate)

-0.072

-0.082

-0.062

Nisvai

-0.064

-0.074

-0.053

Nllng

-0.098

-0.111

-0.086

Northern Alta

-0.069

-0.079

-0.059

Northern Kurdish (Kurmanji)

-0.022

-0.033

-0.011

Pnar

-0.021

-0.035

-0.007

Resígaro

-0.079

-0.089

-0.069

Ruuli

-0.039

-0.048

-0.030

Sadu

-0.124

-0.136

-0.112

Sanzhi Dargwa

-0.135

-0.148

-0.122

Savosavo

-0.052

-0.062

-0.042

Sümi

-0.090

-0.101

-0.079

Svan

-0.066

-0.074

-0.057

Tabaq (Karko)

-0.213

-0.222

-0.203

Tabasaran

-0.138

-0.151

-0.125

Teop

-0.170

-0.181

-0.159

Texistepec Popoluca

-0.070

-0.081

-0.059

Urum

-0.126

-0.134

-0.118

Vera'a

-0.152

-0.163

-0.141

Warlpiri

-0.147

-0.157

-0.137

Yali (Apahapsili)

-0.191

-0.202

-0.179

Yongning Na

-0.128

-0.142

-0.114

Yucatec Maya

-0.067

-0.079

-0.056

Yurakaré

-0.198

-0.204

-0.191

Table 4: The effect of sequence length and position on inter-onset intervals for each human language, computed from the expanded model that includes both length and position. 2.5% and 97.5% denote the lower and upper bounds of the 95% confidence intervals.

Length

Position

Language

Effect

2.5%

97.5%

Effect

2.5%

97.5%

Anal

-0.105

-0.114

-0.096

0.100

0.091

0.109

Arapaho

0.030

0.020

0.039

0.099

0.090

0.109

Asimjeeg Datooga

-0.063

-0.074

-0.053

0.186

0.177

0.196

Baïnounk Gubëeher

-0.102

-0.110

-0.093

0.096

0.088

0.104

Beja

-0.066

-0.073

-0.059

0.065

0.058

0.072

Bora

-0.127

-0.138

-0.116

-0.131

-0.140

-0.123

Cabécar

-0.110

-0.120

-0.100

0.021

0.012

0.031

Cashinahua

-0.100

-0.108

-0.091

-0.019

-0.028

-0.010

Daakie

-0.131

-0.141

-0.122

0.164

0.155

0.173

Dalabon

-0.079

-0.091

-0.066

0.165

0.153

0.177

Dolgan

-0.130

-0.139

-0.121

0.043

0.034

0.052

English (Southern England)

-0.053

-0.066

-0.040

0.050

0.038

0.062

Evenki

-0.101

-0.109

-0.092

0.042

0.033

0.050

Fanbyak

-0.091

-0.101

-0.081

0.161

0.151

0.171

French (Swiss)

-0.050

-0.063

-0.037

0.160

0.151

0.169

Goemai

-0.124

-0.138

-0.110

0.063

0.052

0.074

Gorwaa

-0.125

-0.136

-0.114

0.009

0.000

0.018

Hoocąk

-0.099

-0.109

-0.090

0.141

0.132

0.151

Jahai

-0.062

-0.073

-0.050

0.142

0.131

0.153

Jejuan

-0.093

-0.104

-0.083

0.038

0.028

0.049

Kakabe

-0.123

-0.135

-0.111

0.103

0.091

0.115

Kamas

-0.096

-0.111

-0.082

0.003

-0.012

0.017

Komnzo

-0.081

-0.091

-0.071

0.026

0.018

0.035

Light Warlpiri

-0.144

-0.154

-0.133

0.078

0.067

0.088

Lower Sorbian

-0.078

-0.089

-0.067

0.046

0.037

0.056

Mojeño Trinitario

-0.147

-0.156

-0.137

-0.074

-0.083

-0.065

Movima

-0.014

-0.023

-0.006

-0.053

-0.062

-0.045

Nafsan (South Efate)

-0.072

-0.082

-0.062

0.094

0.085

0.103

Nisvai

-0.064

-0.074

-0.054

0.151

0.144

0.159

Nllng

-0.098

-0.111

-0.086

0.155

0.142

0.167

Northern Alta

-0.069

-0.079

-0.059

0.091

0.081

0.101

Northern Kurdish (Kurmanji)

-0.022

-0.033

-0.011

0.033

0.023

0.042

Pnar

-0.021

-0.035

-0.007

0.087

0.076

0.099

Resígaro

-0.079

-0.089

-0.069

0.012

0.003

0.022

Ruuli

-0.039

-0.048

-0.030

0.069

0.061

0.078

Sadu

-0.124

-0.136

-0.112

0.200

0.189

0.212

Sanzhi Dargwa

-0.135

-0.148

-0.122

0.012

0.000

0.023

Savosavo

-0.052

-0.062

-0.042

-0.125

-0.134

-0.117

Sümi

-0.090

-0.101

-0.080

0.109

0.098

0.120

Svan

-0.066

-0.074

-0.057

-0.026

-0.035

-0.017

Tabaq (Karko)

-0.213

-0.223

-0.203

-0.071

-0.080

-0.061

Tabasaran

-0.138

-0.151

-0.125

-0.025

-0.037

-0.012

Teop

-0.170

-0.181

-0.159

0.072

0.063

0.081

Texistepec Popoluca

-0.070

-0.081

-0.059

0.020

0.011

0.030

Urum

-0.126

-0.134

-0.118

-0.007

-0.015

0.001

Vera'a

-0.152

-0.163

-0.141

0.169

0.160

0.177

Warlpiri

-0.147

-0.157

-0.137

-0.026

-0.035

-0.017

Yali (Apahapsili)

-0.192

-0.203

-0.180

0.140

0.130

0.150

Yongning Na

-0.128

-0.142

-0.114

0.098

0.085

0.112

Yucatec Maya

-0.067

-0.079

-0.056

-0.075

-0.084

-0.066

Yurakaré

-0.198

-0.204

-0.191

-0.035

-0.040

-0.029

1.4 Words in Sentences

The 95% confidence intervals for the effect of sequence length (top) and position (bottom) on element durations and inter-onset intervals for the 16 whale species and 51 human languages. The human language data are comprised of words within sentences. The colors correspond to the taxonomic group and whether the data are element durations (ED) or inter-onset intervals (IOI).

Figure 2: The 95% confidence intervals for the effect of sequence length (top) and position (bottom) on element durations and inter-onset intervals for the 16 whale species and 51 human languages. The human language data are comprised of words within sentences. The colors correspond to the taxonomic group and whether the data are element durations (ED) or inter-onset intervals (IOI).

1.5 Production Constraint Model

James et al. (5) recently found that Menzerath’s law can be detected in pseudorandom sequences of birdsong syllables that are forced to match the durations of real songs. James et al. (5) interpret their model as approximating simple motor constraints, while stronger effects in the real data would indicate additional mechanisms (e.g., communicative efficiency through behavioral plasticity). I originally planned to compare the strength of Menzerath’s law in the real data with simulated data from the model of James et al. (5), as I recently did for house finch song (6), but analyses of language data suggest that it is far too conservative of a null model. 0 of the 51 of languages in the DoReCo dataset exhibit Menzerath’s law to a greater extent than simulated data. Even though many whale species exhibit Menzerath’s law to a greater extent than simulated data from the null model of James et al. (5) (75%; 12 out of 16 species), I do not want to over-interpret this result given the pattern in the human data. Upon further reflection I think that the fundamental assumption of James et al. (5), that sequence durations are governed by motor constraints alone, is unlikely to apply to many species with more complex communication systems. In humpback whales and sperm whales, for example, there appears to be significant inter-individual variation in song and coda length depending on social context (7, 8). More details about this analysis are below.

The production constraint model of James et al. (5) works as follows. For each iteration of the model, a pseudorandom sequence was produced for each real song in the dataset. Syllables were randomly sampled (with replacement) from the population until the duration of the random sequence exceeded the duration of the real song. If the difference between the duration of the random sequence and the real song was < 50% of the duration of the final syllable, then the final syllable was kept in the sequence. Otherwise, it was removed. Each iteration of the model produces a set of random sequences with approximately the same distribution of durations as the real data.

For each species, I generated 100 simulated datasets from the (1) random sequence model and the (2) production constraint model. Then, I fit Menzerath’s law separately to each of the 100 simulated datasets and pooled the model estimates for \(a\) and \(b\) using Rubin’s rule as implemented in the mice package in R. The results can be seen in Figure 3.

Most importantly, the estimated effects from the production constraint model tend to be more negative than those from the real human language data, suggesting that this null model is far too conservative to be informative about “language-like” efficiency.

The point estimates (points) from the real data alongside 95% confidence intervals (bars) from 10 simulated datasets from the production constraint model, for the effect of sequence length on element durations and inter-onset intervals for the 16 whale species and 51 human languages. The human language data are comprised of phonemes within words. The colors correspond to the taxonomic group and whether the data are element durations (ED) or inter-onset intervals (IOI).

Figure 3: The point estimates (points) from the real data alongside 95% confidence intervals (bars) from 10 simulated datasets from the production constraint model, for the effect of sequence length on element durations and inter-onset intervals for the 16 whale species and 51 human languages. The human language data are comprised of phonemes within words. The colors correspond to the taxonomic group and whether the data are element durations (ED) or inter-onset intervals (IOI).

1.6 Median Interpolation

The point estimates from the original datasets (orange) compared to median-interpolated datasets (blue). Interpolating sequences with the median inter-onset interval of each phoneme appears to systematically shift model estimates towards zero (in over 90% of cases).

Figure 4: The point estimates from the original datasets (orange) compared to median-interpolated datasets (blue). Interpolating sequences with the median inter-onset interval of each phoneme appears to systematically shift model estimates towards zero (in over 90% of cases).

1.7 Patterned Burst Pulses

Martin et al. (9) noticed that Heaviside’s dolphins sometimes produce temporally-patterned burst pulses with much more rhythmic variation, especially during social interactions. I analyzed 27 patterned burst pulses provided by Martin et al. (9) and found that they adhere to Menzerath’s law—there is a negative relationship between sequence length and inter-onset intervals (estimate = -0.186, 95% CI: [-0.308, -0.063]).

1.8 Plots with Transformed Axes

The baleen whale (Mysticete) species included in the study (left), alongside the distribution of element durations or inter-onset intervals and sequence lengths (middle) and the slope of Menzerath's law (right). The x- and y-axes have been log-transformed and z-scored to match the structure of the statistical model. Each point in the distribution plots (middle) marks the mean element duration or inter-onset interval, but the slopes on the right were computed from the full set of elements/intervals. The bars in the slope plots (right) mark the 95% confidence intervals around the point estimates.

Figure 5: The baleen whale (Mysticete) species included in the study (left), alongside the distribution of element durations or inter-onset intervals and sequence lengths (middle) and the slope of Menzerath’s law (right). The x- and y-axes have been log-transformed and z-scored to match the structure of the statistical model. Each point in the distribution plots (middle) marks the mean element duration or inter-onset interval, but the slopes on the right were computed from the full set of elements/intervals. The bars in the slope plots (right) mark the 95% confidence intervals around the point estimates.

The toothed whale (Odontocete) species included in the study (left), alongside the distribution of element durations or inter-onset intervals and sequence lengths (middle) and the slope of Menzerath's law (right). The x- and y-axes have been log-transformed and z-scored to match the structure of the statistical model. Each point in the distribution plots (middle) marks the mean element duration or inter-onset interval, but the slopes on the right were computed from the full set of elements/intervals. The bars in the slope plots (right) mark the 95% confidence intervals around the point estimates.

Figure 6: The toothed whale (Odontocete) species included in the study (left), alongside the distribution of element durations or inter-onset intervals and sequence lengths (middle) and the slope of Menzerath’s law (right). The x- and y-axes have been log-transformed and z-scored to match the structure of the statistical model. Each point in the distribution plots (middle) marks the mean element duration or inter-onset interval, but the slopes on the right were computed from the full set of elements/intervals. The bars in the slope plots (right) mark the 95% confidence intervals around the point estimates.

2 Zipf’s Law of Abbreviation

2.1 Effects in Whale Data

Table 5: The effect of count on element duration for each whale species. 2.5% and 97.5% denote the lower and upper bounds of the 95% confidence intervals.

Group

Species

Effect

2.5%

97.5%

Mysticete

Blue Whale

-0.102

-0.139

-0.065

Bowhead Whale

0.368

-0.386

1.121

Humpback Whale

-0.696

-0.943

-0.450

Sei Whale

0.249

-0.422

0.921

Odontocete

Killer Whale

-0.114

-0.314

0.086

2.2 Effects in Human Data

Table 6: The effect of count on element duration for each human language, at the level of phonemes. 2.5% and 97.5% denote the lower and upper bounds of the 95% confidence intervals.

Language

Effect

2.5%

97.5%

Anal

-2.104

-2.613

-1.594

Arapaho

-1.438

-1.704

-1.172

Asimjeeg Datooga

-2.295

-2.952

-1.638

Baïnounk Gubëeher

-1.936

-2.380

-1.492

Beja

-1.455

-1.813

-1.097

Bora

-1.983

-2.394

-1.572

Cabécar

-1.642

-1.935

-1.349

Cashinahua

-2.115

-2.568

-1.663

Daakie

-1.390

-1.788

-0.992

Dalabon

-1.957

-2.426

-1.487

Dolgan

-1.412

-1.731

-1.094

English (Southern England)

-1.065

-1.315

-0.815

Evenki

-1.578

-1.799

-1.357

Fanbyak

-1.230

-1.524

-0.936

French (Swiss)

-0.938

-1.141

-0.736

Goemai

-0.955

-1.238

-0.671

Gorwaa

-2.120

-2.681

-1.559

Hoocąk

-1.314

-1.539

-1.088

Jahai

-1.786

-2.138

-1.435

Jejuan

-1.618

-1.947

-1.289

Kakabe

-1.992

-2.539

-1.446

Kamas

-1.108

-1.376

-0.840

Komnzo

-1.656

-2.085

-1.227

Light Warlpiri

-1.624

-2.168

-1.079

Lower Sorbian

-1.343

-1.688

-0.999

Mojeño Trinitario

-1.436

-1.758

-1.113

Movima

-1.783

-2.134

-1.432

Nafsan (South Efate)

-1.565

-1.870

-1.259

Nisvai

-2.496

-3.049

-1.943

Nllng

-1.859

-2.408

-1.309

Northern Alta

-1.648

-1.981

-1.315

Northern Kurdish (Kurmanji)

-1.412

-1.904

-0.919

Pnar

-1.713

-2.278

-1.149

Resígaro

-1.271

-1.609

-0.934

Ruuli

-1.789

-2.048

-1.530

Sadu

-0.838

-1.178

-0.497

Sanzhi Dargwa

-2.009

-2.598

-1.420

Savosavo

-1.506

-1.990

-1.022

Sümi

-1.395

-1.680

-1.110

Svan

-1.695

-2.095

-1.294

Tabaq (Karko)

-1.727

-2.101

-1.352

Tabasaran

-1.506

-2.085

-0.928

Teop

-1.693

-2.145

-1.242

Texistepec Popoluca

-1.480

-1.755

-1.205

Urum

-1.822

-2.043

-1.600

Vera'a

-1.618

-1.933

-1.302

Warlpiri

-1.962

-2.662

-1.262

Yali (Apahapsili)

-1.414

-1.667

-1.162

Yongning Na

-0.930

-1.281

-0.578

Yucatec Maya

-1.056

-1.257

-0.855

Yurakaré

-2.145

-2.537

-1.753

2.3 Words

The 95% confidence intervals for the effect of count on element duration for the five whale species and 51 human languages. The human language data are comprised of words. The colors correspond to the taxonomic group and whether the data are element durations (ED) or inter-onset intervals (IOI).

Figure 7: The 95% confidence intervals for the effect of count on element duration for the five whale species and 51 human languages. The human language data are comprised of words. The colors correspond to the taxonomic group and whether the data are element durations (ED) or inter-onset intervals (IOI).

2.4 Plot with Transformed Axis

The whale species included in the study (left), alongside the distribution of element durations and counts (middle) and the slope of Zipf's law of abbreviation (right). The x-axis has been z-scored, and the y-axis has been z-scored and log-transformed, to match the structure of the statistical model. Each point in the distribution plots (middle) marks the mean duration of elements, but the slopes on the right were computed from the full set of elements. The bars in the slope plots (right) mark the 95% confidence intervals around the point estimates.

Figure 8: The whale species included in the study (left), alongside the distribution of element durations and counts (middle) and the slope of Zipf’s law of abbreviation (right). The x-axis has been z-scored, and the y-axis has been z-scored and log-transformed, to match the structure of the statistical model. Each point in the distribution plots (middle) marks the mean duration of elements, but the slopes on the right were computed from the full set of elements. The bars in the slope plots (right) mark the 95% confidence intervals around the point estimates.

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