Absolute Brain Size Predicts Dog Breed Differences in Executive Function

Daniel J. Horschler1,*, Brian Hare2,3, Josep Call4,5, Juliane Kaminski6, Ádám Miklósi7,8, & Evan L. MacLean1

Supplementary Material

1School of Anthropology, University of Arizona, Tucson, AZ, 85719, United States2Department of Evolutionary Anthropology, Duke University, Durham, NC, 27708, United States3Center for Cognitive Neuroscience, Duke University, Durham, NC, 27708, United States4Department of Developmental and Comparative Psychology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany5School of Psychology and Neuroscience, University of St Andrews, St Andrews, United Kingdom6Department of Psychology, University of Portsmouth, Portsmouth, United Kingdom7Department of Ethology, Eötvös Loránd University, Budapest, Hungary8MTA-ELTE Comparative Ethology Research Group, Budapest, Hungary*Correspondence - Email: horschler@email.arizona.edu; Phone: 520-621-2646

Method Details

Cognitive Data. Cognitive data were compiled from the Dognition.com database.

Dognition.com is a citizen science website that provides dog owners with instructions for

completing cognitive experiments with pet dogs in their homes. Participants receive written and

video instructions for the behavioral protocols, and electronically submit data on their dog’s

responses as activities are completed. We included data from ten cognitive tasks in our analyses:

Yawning, Eye Contact, Arm Pointing, Foot Pointing, Cunning, Memory vs. Pointing, Memory

vs. Smell, Delayed Memory, Inferential Reasoning, and Physical Reasoning. For detailed

protocols of each task, see Task Details.

We analyzed all subjects from a dataset originally including 18,610 dogs, with the

majority of these dogs having completed multiple tasks. To ensure that our sample included only

adult dogs, we removed all data from dogs who were 1 year or younger at the time of testing (n =

2,307). Because our analyses focused on breed-average performance, we eliminated data from

dogs that were identified as mixed breeds, or for whom the breed identity was not known (n =

5,311; both measures determined by owner report). We also eliminated data from a small subset

of poodles with reported body weights intermediate to miniature and standard morphs (n = 22,

see Morphological Data). Lastly, to ensure representative samples across breeds we removed

data from breeds represented by less than 20 individuals (on a task-wise basis), as well as for

breeds which lacked body weight or genetic data (n = 3,573 individuals) from the primary

sources these data were compiled from (see below). The final dataset we analyzed included

7,397 dogs. Demographic data for each breed included in our analyses is shown in

Supplementary Table 1.

Data Collection Process. All text in this section and in the following Task Details

section was directly adapted from Stewart et al. (2015). All participants received instructions

recommending cognitive tasks be conducted at home in a familiar room reasonably free of

distractions. Participants were encouraged to take breaks whenever the dog lost motivation, and

were repeatedly reminded not to intentionally influence their dog’s choices, although

experimental evidence suggests that the effect of unconscious cuing on dogs during cognitive

experiments may not be as ubiquitous as has often been suggested (Hauser, Comins, Pytka,

Cahill, & Velez-Calderon, 2011; Pongrácz, Miklósi, Bálint, & Hegedüs, 2013; Schmidjell,

Range, Huber, & Virányi, 2012). Regardless, instructions were worded to frequently remind

participants that there “are no correct answers” and to let their dog choose freely.

For each task, participants watched a how-to video that detailed the experimental setup,

procedural protocol, and the set of possible responses from their dog that they would need to live

code. Written instructions and a Frequently Asked Questions (FAQ) section were also provided,

and a link to the FAQ was available at all times in case questions arose during testing.

Participants were not able to advance through tasks or trials out of order, to help ensure that

participants correctly followed all steps, and repeated each trial the correct number of times.

Once all of the steps were complete for each trial, participants were asked to code their dog’s

behavior. The majority of decisions involved either stopping a timer or indicating which of two

locations the dog approached first.

Participants were instructed to work with a partner unless their dog was able to sit and

stay on their own. Video and written instructions emphasized the importance of staring directly

ahead after releasing the dog, and of releasing the dog without nudging, pushing, or leading the

dog in one direction or the other. In the instructional video, the dog was positioned directly

across from the experimenter, approximately 1.8m away. Three post-it notes were placed on a

line perpendicular to the dog and the experimenter. The center post-it was placed 0.6m directly

in front of the experimenter, while the other two were placed 0.9m on either side of the center

post-it. Once participants completed this set up, they advanced to step-by-step instructions for

each trial.

Task Details. The vast majority of dogs were tested using the following task order:

Yawning, Eye Contact, Arm Pointing, Foot Pointing, Cunning, Memory vs. Pointing, Memory

vs. Smell, Delayed Memory, Inferential Reasoning, and Physical Reasoning. Non-differential

rewarding (in which any choice was rewarded) was used in Arm Pointing, Foot Pointing, and

Cunning, while differential rewarding was used in Memory vs. Pointing, Memory vs. Smell,

Delayed Memory, Inferential Reasoning, and Physical Reasoning.

Task Details: Yawning. The Yawning task procedure was based on Joly-Mascheroni et al.

(2008). Participants watched a video of instructions that included examples of dogs yawning.

Participants were instructed to sit on the floor with the dog, but not to touch or interact with the

dog at any point during the yawning conditions. In the control condition, the participant was

prompted to say the word “yellow” every 5 seconds for 30 seconds. In the experimental

condition, the participant was instructed to yawn clearly and audibly every 5 seconds for 30

seconds. Once this 30-second period ended, a 2-minute timer started. During the 30-second

manipulation and the 2 minutes that followed, the participants were instructed to observe if the

dog yawned. They were prompted to code whether the dog yawned after each trial (they were not

asked for a frequency). There was only one trial of each condition, and all subjects received the

control condition first.

Task Details: Eye Contact. Procedurally, the Eye Contact task was based on Nagasawa et al.

(2009). Participants first conducted a warm-up condition, in which the participant was instructed

to stand facing their dog with the dog standing or sitting ~1.8 meters away. The participant was

then prompted to call the dog’s name, show the dog a small treat, and place that treat directly

beneath their eye and to start the 10-second timer. Once time elapsed, the participant was

prompted to give the dog the treat. No coding was required and the warm-up was repeated three

times. The experimental condition was the same as the warm-up except that the participant was

instructed to stop the timer once the dog broke eye contact for more than two seconds. If the dog

never broke eye contact, the trial ended after 90 seconds. Three trials of this condition were

conducted.

Task Details: Arm Pointing and Foot Pointing. The Arm Pointing task was based on Gácsi et

al. (2009) while the Foot Pointing task was based on Lakatos et al. (2009). In the pointing warm-

up, the dog was introduced to the two potential locations to find a treat. The participant was

instructed to stand ~1.8m away from the dog, call the dog’s name, show the dog a treat, and

place the treat down on the ground at arm’s length to either the left or right (~1.2m apart). The

instructions indicated which side to place the treat on in each trial. The treat location was

counterbalanced across trials and participants never placed a treat on the same side on two

consecutive trials. Once the participant had placed the treat, they were instructed to release the

dog while giving a release command. After each trial, the participant was asked to record if the

dog retrieved the treat. There were six trials in this warm-up.

The Arm Pointing and Foot Pointing conditions were identical to the warm-up except that

two identical food treats were placed at arm’s length on either side. Participants were instructed

which location they were to gesture toward and to allow the dog to retrieve both treats while

recording which location the dog approached first. A first approach was illustrated in the video

and was defined as crossing the plane created by the post-it notes on the left or right. In the Arm

Pointing condition, participants were to point by extending their arm, hand, and index finger

toward one location while standing equidistant between the two locations. In the Foot Pointing

condition, participants were instructed to take one step toward one location while extending their

leg and food in the direction of the other location. In both experimental conditions, gaze and

gesture was to be directed at the location being indicated until the dog made their choice. Six

trials were conducted in each condition.

Task Details: Cunning. The Cunning (Other’s Visual Cues) task was procedurally based on

Call et al. (2003). In the baseline watching condition, the dog was positioned ~1.8m from the

participant. The participant was then instructed to say the dog’s name and “No” or “Leave it”

twice, clearly and loudly, while placing a treat in front of them on the ground. Once the

participant stood back up, they activated the countdown timer, which they only stopped when the

dog approached and ate the forbidden food. The timer automatically stopped after 90 seconds if

the dog never approached. The two experimental conditions were identical to the baseline

condition except that the participant did not watch the treat. In the back turned condition, the

participant immediately turned their back to the dog, while in the eyes covered condition, the

participant covered their eyes with their hands. If a partner was helping, they were also instructed

to turn their back. Participants were instructed to look over their shoulder every few seconds or

to peer through their fingers subtly to detect when the dog approached. Two trials of the back

turned and eyes covered condition were conducted. One watching trial was conducted before and

after the four experimental conditions. The two back turned conditions always preceded the eyes

covered trials.

Task Details: Memory vs. Pointing, Memory vs. Smell, and Delayed Memory. Dogs were

first introduced to finding food hidden underneath cups. The participant started by standing

~1.8m away from the dog, and placing one opaque cup upside down on the left or right at arm’s

length (~1.2m apart). In the first condition of the warm-up task, the participant was instructed to

call the dog’s name and show the dog a treat. The participant then placed this treat underneath

the cup as their dog watched. The second warm-up condition was the same as the one-cup warm-

up except the participant placed a cup at arm’s length on both the left and right simultaneously.

Then they placed a treat under one of the two cups as their dog watched. The treat location was

counterbalanced across trials and participants never placed a treat on the same side on two

consecutive trials. Once the treat had been placed under the cup, the participant gave a release

command. A first approach was illustrated in the video and was defined as crossing between the

plane created by the center-left or center-right post-it notes. If the dog chose the side with the

treat, the dog was allowed to eat the treat. If the dog chose the side without the treat, the

participant was instructed to show the dog where the treat was located, but to prevent the dog

from eating the treat. After each trial the participant was prompted to record if the dog retrieved

the treat. Four trials of each warm-up condition were administered for a total of eight warm-up

trials.

The Memory vs. Smell procedure was based on a similar comparison in Szetei et al.

(2003). This task was identical to the two-cup warm-up, except that while the dog’s view was

occluded, the treat was switched to the opposite cup in which it was initially hidden (suggestions

for blocking the dog’s view included (1) covering the dog’s eyes with the partner’s hands, (2)

turning the dog around while distracting it, or (3) kneeling in front of the dog while holding its

head). Four trials were conducted.

The Memory vs. Pointing procedure was also was based on a similar condition in Szetei

et al. (2003). Memory vs. Pointing was identical to the two-cup warm-up except that once the

food was hidden, the participant extended their arm, hand, and index finger toward the empty

cup. Six trials of this condition were conducted.

Finally, the Delayed Memory procedure was based on Fiset et al. (2003) and MacLean et

al. (unpublished data). The Delayed Memory task was the same as the two-cup warm-up except

that after the food was placed, participants waited increasingly longer delays before releasing

their dog to search for the hidden food. In the first trial the countdown timer ran for 60 seconds,

increasing by 30 seconds per trial for three more trials. The delay for the last trial lasted for 150

seconds.

Task Details: Inferential and Physical Reasoning. The Inferential Reasoning task was based

on the procedure of Erdohegyi et al. (2007). In a warm-up condition, the participant was

instructed to stand ~1.8m away from the dog, and to place two cups at arm’s length to the left

and right (~1.2m apart). Both cups were placed on their side with the inside of the cup facing the

dog. The participant was then instructed to call the dog’s name and show the dog a treat. The

participant then blocked the dog’s view of the treat in their hand with an opaque occluder. They

next baited one cup while sham baiting the other. Regardless of where the treat was hidden, the

participant was instructed to always move from the right cup to the left cup. The treat location

was counterbalanced across trials and participants never placed a treat on the same side on two

consecutive trials.

Once the participant had baited or sham-baited both the right and left cup, they placed the

barrier behind them and left the cups laying flat with open sides facing the dog (so that the dog

could easily see the treat in one of the cups). To help the dog see the treat clearly, the participant

lifted both cups simultaneously, bringing them together at the dog’s approximate eye level. They

then placed them upside down to hide the food’s location. Dogs simply had to remember where

they saw the food hidden when released. After each trial, the participant was asked to record if

the dog retrieved the treat. Six trials of this warm-up were conducted.

In the Inferential Reasoning task, the procedure was the same as the warm-up except that

after baiting the cups, they were flipped upside down without showing the dog where the food

was hidden. Then the participant showed the dog which cup was empty by lifting the empty cup

and bringing it to the dog’s approximate eye level. After placing the empty cup back down, the

dog was released to search. Four trials of this experimental condition were conducted.

In the Physical Reasoning task warm-up, the participant folded two pieces of standard

U.S. (8.5” x 11”) paper width-wise so that when placed on the ground, they remained flat. One

piece of paper was then placed at arm’s length on the left or right. The participant was then

instructed to call the dog’s name and show the dog a treat. They next occluded the baiting of the

hiding location by holding an opaque barrier in front of the hand with food. The participant then

wedged the treat in the crease of the paper, propping one side of the paper up. Once the

participant had hidden the treat, they placed the barrier behind them and the dog was released to

search. If the dog approached close enough to touch the paper, the participant could either let the

dog open the paper or fold the paper down to help the dog access the food. If the dog did not

approach the paper after 90 seconds, the participant would show the location of the treat to the

dog and allow him/her to eat it. After each trial, the participant was asked to record if the dog

retrieved the treat. There were four trials in this condition.

In the Physical Reasoning experimental condition, based on Bräuer et al. (2006), the

procedure was the same as the warm-up except that the participant placed a folded piece of paper

on the left and right at arm’s length. They then occluded the baiting and sham-baiting as they

propped one of the pieces of paper up using the treat. Counterbalancing was automated so that

the first side baited alternated equally between left and right across dogs and within the test

session of any one dog. After each trial, the participant was instructed to record if the dog

retrieved the treat. There were four trials in this condition.

Morphological Data. As a measure of breed-typical body mass, we used breed-mean

body weights from the Canine Behavioral Assessment and Research Questionnaire (C-BARQ).

The C-BARQ is a 100-item survey completed by dog owners and used to quantify the behavioral

and temperamental characteristics of dogs (Hsu & Serpell, 2003; McGreevy et al., 2013).

Owners are prompted to enter their dog’s body weight and breed as a part of the survey.

Although Dognition.com does collect data on dogs’ body weights, these values are entered in

10lb (4.6kg) increments limiting precision in estimating breed averages, particularly for small

breeds.

Because the American Kennel Club (AKC) considers all poodles (Toy, Miniature, and

Standard) as one breed, Dognition.com does not distinguish between these morphs.

Consequently, there was large variation in the reported body weights of poodles in our sample.

From 10 to 70lbs, there were at least 10 individuals reported in each 10lb increment (n = 274

poodles in total). To more precisely model breed-typical brain weight within this sample, we

split poodles into “miniature poodle” and “standard poodle” denominations based on body

weights reported on Dognition.com. Using the C-BARQ database as a reference for the average

weights of miniature poodles (mean = 15.47lbs, SD = 4.74lbs) and standard poodles (mean =

48.64lbs, SD = 15.43lbs), we grouped all poodles with a reported weight of 10 or 20lbs (n = 97)

into the miniature poodle denomination, and all poodles with a reported weight greater than

40lbs (n = 155) into the standard poodle denomination. We excluded poodles with a reported

weight of 30lbs (n = 22) because these values were intermediate to the two categories. Including

these two poodle denominations, there were a total of 184 breeds in the Dognition.com database

for which we were also able to obtain body weight data from the C-BARQ.

Validation of dog brain weight measures. To estimate brain weight for each breed in

our sample, we used a brain weight-body weight scaling power function for dogs reported by

Bronson (1979), and validated this model using a sample of 24 breeds with known brain weights.

As a measure of breed-typical body weight, we used breed-mean body weights from the Canine

Behavioral Assessment and Research Questionnaire (C-BARQ) (Hsu & Serpell, 2003;

McGreevy et al., 2013). We excluded two breeds with brain weights reported in Bronson (1979)

from our validation: toy poodle because we do not use this breed designation in our cognitive

analyses, and standard schnauzer because this was the only breed for which the body weight

reported in (Bronson, 1979) (7.9kg) was more than two standard deviations smaller than the

body weight reported on the C-BARQ (15.6kg).

The equation representing Bronson’s power function is y = 0.27x + 1.60, where ‘x’ is a

base 10 logarithmic (log10) transformation of body weight in kilograms, and ‘y’ is a log10

transformation of brain weight in grams. Across 24 breeds with brain weights reported in

Bronson (1979), C-BARQ breed-mean body weight was a significant predictor of brain weight, β

= 0.28, t(22) = 14.71, p < .001, explaining 91% of the variance in brain weight (SE = 0.03; see

Figure S1). For the estimated brain weights of all 74 breeds in our sample, see Supplementary

Table 2.

To ensure that differences in skull shape between breeds did not cause systematic

inaccuracies in our estimated brain weight values, we compiled cephalic index (CI)

measurements from breeds reported in McGreevy et al. (2013) and Boyko et al. (2010). CI was

calculated as maximum skull width multiplied by 100, and then divided by maximum skull

length. There were 19 breeds which had both an observed brain weight reported in (Bronson,

1979) and a CI value reported in either McGreevy et al. (2013) or Boyko et al. (2010). Using k-

means clustering to partition CI values from these breeds into both 2 and 3 clusters respectively,

we observed no systematic overestimation or underestimation of brain weight based on CI in our

sample, consistent with previous studies (Carreira, 2016).

Statistical Analysis. To control for genetic relatedness between breeds, the associations

between estimated brain weight and cognitive measures were tested using Efficient Mixed

Modeling for Association studies (EMMA) (Kang et al., 2008; Zhou & Stephens, 2012). Genetic

covariance between breeds was incorporated using a breed-average identity-by-state (IBS)

matrix (Boyko et al., 2010), using molecular data from Hayward et al. (2016). Tests were

conducted using the ‘EMMREML’ package (Akdemir & Godfrey, 2015) in the R environment

(v.3.3.1) (R Core Team, 2016). Relationships were considered significant at an alpha level of

0.05.

After filtering out the only breed included in our dataset for which no genetic data were

available (miniature Australian shepherd), there were 7,397 individuals representing 74 breeds

available for analyses (see Supplementary Table 2). Breeds with at least 20 individuals having

completed any singular task were included in that task’s analyses regardless of how many

individuals of that breed completed the other tasks. Average task performance by breed is shown

in Supplementary Table 3.

Additional Results

Associations between brain size and cognition vary across cognitive domains. To

explore whether behavioral data were stable across trials within tasks significantly associated

with estimated brain weight and whether any variation over time differed as a function of

estimated brain weight, we fit repeated measures mixed-models predicting task performance

from trial number alone, as well as from a trial number by estimated brain weight interaction

term. In Cunning, the Watching condition of Cunning alone, and Memory vs Pointing, trial

number was a significant predictor of task performance (Cunning: β = -0.61, t(219) = -4.66, p <

0.001; [Cunning] Watching: β = -0.74, t(43) = -4.19, p < 0.001; Memory vs. Pointing: β = 0.001,

t(179) = 2.46, p = 0.01). In the Watching condition of the Cunning task, dogs took significantly

less time to pilfer the forbidden food over the course of the trials, while in Memory vs. Pointing,

dogs became less likely to follow the pointing gesture over time. In Arm Pointing and the Not

Watching condition of Cunning alone, trial number was not a significant predictor of task

performance (Arm Pointing: β = -0.00005, t(294) = -0.024, p = 0.98; [Cunning] Not Watching: β

= -0.29, t(131) = -1.29, p = 0.20). In no cases were there any significant trial number by

estimated brain weight interactions (Arm Pointing: β = 0.00003, t(293) = 0.22, p = 0.83;

Cunning: β = 0.007, t(218) = 0.87, p = 0.38; [Cunning] Watching: β = 0.016, t(42) = 1.44, p =

0.16; [Cunning] Not Watching: β = -0.014, t(130) = -1.00, p = 0.32; Memory vs. Pointing: β =

0.0002, t(178) = 0.63, p = 0.53). The lack of significant interactions between trial number and

brain weight demonstrates that while performance did vary as a function of trial number in three

of the above measures, it did not vary differentially as a function of brain weight. We were

unable to assess the potential for changes in performance due to learning across trials in the

Delayed Memory task, because each subsequent trial of this task is more difficult than the last

(i.e. delay length increases with each trial), so performance is expected to vary as a function of

trial number by design.

Body size. Comparisons of linear models predicting cognitive measures from breed-

average body weight and estimated brain weight respectively revealed that for most measures in

which performance was significantly associated with estimated brain weight in our main

analyses, models predicting cognitive measures from estimated brain weight (Arm Pointing:

Adjusted R2 = 0.03, AIC = -201.86; Cunning: Adjusted R2 = 0.22, AIC = 221.48; Memory vs.

Pointing: Adjusted R2 = 0.08, AIC = -99.09; Delayed Memory: Adjusted R2 = 0.27, AIC = -

107.58) explained more of the variance in each cognitive measure and had a lower AIC than

models predicting cognitive measures from body weight (Arm Pointing: Adjusted R2 = 0.02, AIC

= -201.24; Cunning: Adjusted R2 = 0.19, AIC = 223.42; Memory vs. Pointing: Adjusted R2 =

0.07, AIC = -98.79; Delayed Memory: Adjusted R2 = 0.24, AIC = -106.29). However, this was

not true in all cases (Brain weight models -- [Cunning] Watching: Adjusted R2 = 0.17, AIC =

335.94; [Cunning] Not Watching: Adjusted R2 = 0.28, AIC = 334.14; Body weight models --

[Cunning] Watching: Adjusted R2 = 0.18, AIC = 335.22; [Cunning] Not Watching: Adjusted R2

= 0.28, AIC = 333.87), and differences in AIC and adjusted R2 were generally too small to draw

meaningful conclusions about which models fit the cognitive data better. Results from mixed-

models (controlling for genetic relatedness) predicting cognitive performance from CBARQ-

reported breed-average body weight for each task within the same sample as our main breed-

level analyses are presented in Supplementary Table 5, and corresponding plots are displayed in

Supplementary Figure 2.

Supplementary Table 1

Breed Body Weight (kg) Estimated Brain Weight (g) Age Male FemaleAiredale Terrier 25.74 ± 0.49 96.54 4.50 13 9Akita 40.91 ± 0.65 109.64 4.43 11 15Alaskan Malamute 38.42 ± 0.78 107.77 4.57 10 12American Eskimo Dog 11.38 ± 0.41 77.15 7.55 16 14American Pit Bull Terrier 26.29 ± 0.27 97.10 4.81 64 72American Staffordshire Terrier

26.05 ± 0.46 96.864.65 27 21

Australian Cattle Dog 19.72 ± 0.23 89.72 5.34 42 43Australian Shepherd 20.52 ± 2.61 90.71 5.16 165 146Basset Hound 24.63 ± 0.62 95.38 5.87 21 12Beagle 12.79 ± 0.20 79.66 6.51 75 62Belgian Malinois 26.83 ± 0.38 97.65 4.48 19 25Bernese Mountain Dog 41.35 ± 0.50 109.97 4.34 28 17Bichon Frise 6.78 ± 0.16 66.90 6.66 39 36Border Collie 18.84 ± 0.15 88.60 5.33 191 163Border Terrier 7.99 ± 0.26 69.98 5.57 21 15Boston Terrier 9.41 ± 0.22 73.22 5.81 62 42Boxer 28.16 ± 0.33 98.95 5.19 101 72Brittany 17.60 ± 0.31 86.96 5.02 25 27Bulldog 24.08 ± 0.65 94.78 4.38 42 43Cairn Terrier 7.64 ± 0.19 69.15 6.73 21 20Cardigan Welsh Corgi 13.78 ± 0.45 81.30 5.99 11 12Cavalier King Charles Spaniel 7.99 ± 0.19 69.99 4.92 47 42Chihuahua 3.35 ± 0.07 55.10 5.96 75 85Cocker Spaniel 11.72 ± 0.17 77.76 5.79 54 46Collie 28.12 ± 0.38 98.91 5.43 21 28Coton de Tulear 5.86 ± 0.41 64.28 5.11 19 19Dachshund 7.20 ± 0.16 68.03 6.19 90 78Dalmatian 25.76 ± 0.47 96.56 5.57 11 17Doberman Pinscher 33.77 ± 0.31 104.01 5.16 71 37English Cocker Spaniel 12.93 ± 0.17 79.89 6.16 15 17English Springer Spaniel 20.05 ± 0.26 90.13 5.61 64 48Flat-Coated Retriever 28.81 ± 0.68 99.57 4.71 23 13French Bulldog 11.51 ± 0.24 77.38 4.46 53 41German Shepherd Dog 34.50 ± 0.20 104.63 4.86 264 264German Shorthaired Pointer 26.27 ± 0.52 97.08 5.94 30 21Golden Retriever 31.04 ± 0.22 101.63 5.32 338 322Great Dane 57.75 ± 0.80 120.54 5.15 24 25Greyhound 30.89 ± 0.39 101.50 6.03 32 27Havanese 5.72 ± 0.12 63.85 5.06 52 41Irish Water Spaniel 27.81 ± 1.00 98.61 6.46 34 28Italian Greyhound 5.39 ± 0.22 62.83 5.87 14 10Jack Russell Terrier 7.55 ± 0.13 68.92 6.39 45 41

Labrador Retriever 31.59 ± 0.17 102.12 5.57 562 534Lhasa Apso 7.83 ± 0.26 69.61 5.60 13 8Maltese 4.45 ± 0.13 59.58 7.17 39 35Miniature Pinscher 5.28 ± 0.16 62.47 6.46 24 26Miniature Poodle 7.02 ± 0.17 67.54 6.27 67 39Miniature Schnauzer 7.89 ± 0.14 69.76 6.01 97 64Newfoundland 57.39 ± 0.55 120.33 4.96 21 12Papillon 3.97 ± 0.12 57.74 6.68 20 26Parson Russell Terrier 7.55 ± 0.22 68.90 6.49 41 22Pembroke Welsh Corgi 12.73 ± 0.23 79.55 5.18 50 37Pomeranian 4.32 ± 0.14 59.11 5.78 38 31Portuguese Water Dog 21.86 ± 0.37 92.29 5.40 38 31Pug 8.79 ± 0.17 71.85 5.86 58 41Rat Terrier 7.11 ± 0.22 67.79 7.19 24 23Rhodesian Ridgeback 37.68 ± 0.43 107.20 4.41 35 31Rottweiler 42.02 ± 0.36 110.46 5.27 39 43Samoyed 25.31 ± 0.80 96.09 4.88 12 13Shetland Sheepdog 10.48 ± 0.20 75.40 5.94 74 50Shiba Inu 10.61 ± 0.18 75.67 5.34 29 20Shih Tzu 6.28 ± 0.13 65.52 6.02 94 56Siberian Husky 23.88 ± 0.34 94.56 5.33 41 47Soft Coated Wheaten Terrier 16.42 ± 0.17 85.32 5.76 36 37St. Bernard 59.75 ± 1.55 121.67 4.06 13 9Staffordshire Bull Terrier 18.58 ± 0.42 88.26 5.75 17 20Standard Poodle 22.06 ± 0.35 92.53 5.56 143 115Standard Schnauzer 15.58 ± 0.56 84.09 5.39 18 14Tibetan Terrier 10.73 ± 0.39 75.90 5.11 9 15Vizsla 22.97 ± 0.42 93.57 5.28 42 32Weimaraner 30.71 ± 0.53 101.33 5.92 35 26West Highland White Terrier 8.01 ± 0.17 70.04 6.29 37 38Whippet 14.20 ± 0.22 81.97 5.30 24 13Yorkshire Terrier 3.72 ± 0.10 56.72 5.94 69 62

Supplementary Table 1. Mean body weight (± SEM, as reported on the C-BARQ), estimated brain weight, mean age, and sex breakdown for each of the 74 breeds that were included in our analyses. Average ages and sex breakdowns include all purebred dogs of each breed for which demographic information was submitted to Dognition.com, regardless of which cognitive tasks individuals completed.

Supplementary Table 2

Breed Yawn Eye Arm Foot Cunn MvP MvS Mem IR PRAiredale Terrier 20 - - - - - - - - -Akita 22 21 - - - - - - - -Alaskan Malamute 20 - - - - - - - - -American Eskimo Dog 30 28 21 - - - - - - -American Pit Bull Terrier 127 111 72 63 46 33 32 30 25 23American Staffordshire Terrier 42 36 24 21 - - - - - -Australian Cattle Dog 79 71 45 42 33 29 27 27 21 21Australian Shepherd 295 267 219 206 151 132 119 115 92 90Basset Hound 26 24 - - - - - - - -Beagle 121 107 85 81 56 50 47 45 42 41Belgian Malinois 42 37 31 28 - - - - - -Bernese Mountain Dog 42 36 26 26 - - - - - -Bichon Frise 67 62 37 33 23 - - - - -Border Collie 326 301 205 195 142 116 106 103 88 83Border Terrier 33 30 23 22 - - - - - -Boston Terrier 92 83 55 54 35 20 20 20 - -Boxer 158 148 98 88 62 47 45 44 37 37Brittany 49 42 31 29 22 20 - - - -Bulldog 84 72 48 43 30 22 20 20 - -Cairn Terrier 38 33 21 20 - - - - - -Cardigan Welsh Corgi 22 20 - - - - - - - -Cavalier King Charles Spaniel 82 70 48 44 30 22 21 21 - -Chihuahua 141 120 70 68 44 33 30 29 23 23Cocker Spaniel 90 77 50 44 33 27 25 25 21 21Collie 48 42 31 30 23 20 - - - -Coton de Tulear 37 32 26 25 21 - - - - -Dachshund 158 136 82 77 51 42 40 36 29 29Dalmatian 28 24 - - - - - - - -Doberman Pinscher 96 81 62 59 47 41 36 36 31 30English Cocker Spaniel 30 22 - - - - - - - -English Springer Spaniel 108 93 68 66 41 33 32 31 26 24Flat-Coated Retriever 35 33 23 22 - - - - - -French Bulldog 87 75 50 46 35 26 23 23 - -German Shepherd Dog 497 434 293 273 197 172 162 157 133 130German Shorthaired Pointer 44 43 27 26 - - - - - -Golden Retriever 609 540 411 382 277 220 211 204 171 163Great Dane 44 39 27 24 - - - - - -Greyhound 54 48 31 30 21 - - - - -Havanese 85 76 53 50 32 27 26 25 20 -Irish Water Spaniel 62 62 60 59 56 56 55 55 53 53Italian Greyhound 22 - - - - - - - - -Jack Russell Terrier 71 53 32 31 23 - - - - -Labrador Retriever 1021 909 657 613 479 408 378 365 306 293

Lhasa Apso 21 - - - - - - - - -Maltese 69 61 32 27 - - - - - -Miniature Pinscher 46 39 27 26 20 - - - - -Miniature Poodle 96 87 57 57 45 43 39 36 31 31Miniature Schnauzer 152 137 97 90 58 49 47 46 41 39Newfoundland 32 26 - - - - - - - -Papillon 44 38 27 21 - - - - - -Parson Russell Terrier 59 52 31 30 - - - - - -Pembroke Welsh Corgi 83 71 54 53 42 36 35 35 28 28Pomeranian 58 52 30 26 21 - - - - -Portuguese Water Dog 69 62 49 47 35 27 24 23 21 -Pug 89 77 48 42 29 25 25 25 21 20Rat Terrier 43 38 22 21 - - - - - -Rhodesian Ridgeback 62 55 40 38 26 - - - - -Rottweiler 76 64 45 40 29 26 24 22 - -Samoyed 23 23 - - - - - - - -Shetland Sheepdog 117 107 76 74 60 52 51 51 41 39Shiba Inu 47 44 26 26 - - - - - -Shih Tzu 135 116 75 66 42 35 34 34 25 22Siberian Husky 81 74 51 48 29 29 26 24 24 24Soft Coated Wheaten Terrier 67 60 46 42 32 28 26 25 - -St. Bernard 21 20 - - - - - - - -Staffordshire Bull Terrier 31 29 - - - - - - - -Standard Poodle 241 209 160 154 110 93 85 79 62 58Standard Schnauzer 31 24 - - - - - - - -Tibetan Terrier 20 - - - - - - - - -Vizsla 73 68 44 43 33 26 23 22 - -Weimaraner 55 52 35 33 24 - - - - -West Highland White Terrier 70 60 43 39 26 25 25 25 - -Whippet 35 30 20 20 - - - - - -Yorkshire Terrier 114 100 65 61 39 33 30 30 20 -Total 7344 6413 4342 4044 2710 2123 1949 1888 1432 1322

Supplementary Table 2. Number of individuals representing each of the 74 breeds included in each task in the cognitive analyses. Breeds with less than 20 individuals having completed a given task were excluded from that task’s analyses. Tasks are presented in order conducted from first to last, and are abbreviated as follows: Yawn = Yawning, Eye = Eye Contact, Arm = Arm Pointing, Foot = Foot Pointing, Cunn = Cunning, MvP = Memory vs. Pointing, MvS = Memory vs. Smell, Mem = Delayed Memory, IR = Inferential Reasoning, and PR = Physical Reasoning.

Supplementary Table 3

Breed Yawn Eye Arm Foot Cunn MvP MvS Mem IR PRAiredale Terrier -0.10 ± 0.12 - - - - - - - - -Akita 0.09 ± 0.09 36.83 ± 4.50 - - - - - - - -Alaskan Malamute 0.10 ± 0.12 - - - - - - - - -American Eskimo Dog 0.13 ± 0.10 52.36 ± 4.67 0.59 ± 0.05 - - - - - - -American Pit Bull Terrier -0.04 ± 0.05 43.87 ± 2.24 0.67 ± 0.02 0.65 ± 0.03 -3.15 ± 2.12 0.70 ± 0.05 0.74 ± 0.05 0.84 ± 0.04 0.47 ± 0.05 0.59 ± 0.04American Staffordshire Terrier 0.07 ± 0.08 45.44 ± 3.84 0.56 ± 0.03 0.59 ± 0.05 - - - - - -Australian Cattle Dog -0.05 ± 0.06 50.75 ± 2.82 0.66 ± 0.03 0.64 ± 0.04 -3.86 ± 2.89 0.69 ± 0.06 0.72 ± 0.04 0.81 ± 0.04 0.43 ± 0.04 0.64 ± 0.04Australian Shepherd 0.00 ± 0.03 57.29 ± 1.51 0.69 ± 0.01 0.67 ± 0.01 0.30 ± 1.38 0.71 ± 0.03 0.74 ± 0.02 0.83 ± 0.02 0.50 ± 0.02 0.60 ± 0.02Basset Hound 0.04 ± 0.13 50.04 ± 5.52 - - - - - - - -Beagle -0.02 ± 0.05 56.22 ± 2.50 0.63 ± 0.02 0.63 ± 0.02 3.09 ± 1.88 0.73 ± 0.03 0.81 ± 0.03 0.82 ± 0.03 0.46 ± 0.04 0.60 ± 0.04Belgian Malinois 0.12 ± 0.11 58.84 ± 3.95 0.68 ± 0.04 0.70 ± 0.03 - - - - - -Bernese Mountain Dog 0.02 ± 0.09 50.04 ± 4.09 0.76 ± 0.04 0.71 ± 0.05 - - - - - -Bichon Frise -0.03 ± 0.05 50.28 ± 3.21 0.64 ± 0.03 0.67 ± 0.04 2.84 ± 5.04 - - - - -Border Collie 0.02 ± 0.03 46.60 ± 1.43 0.69 ± 0.02 0.67 ± 0.02 -0.13 ± 1.38 0.62 ± 0.03 0.72 ± 0.03 0.80 ± 0.02 0.46 ± 0.03 0.66 ± 0.03Border Terrier 0.03 ± 0.08 59.44 ± 5.08 0.65 ± 0.04 0.69 ± 0.04 - - - - - -Boston Terrier -0.05 ± 0.05 60.01 ± 2.91 0.60 ± 0.03 0.60 ± 0.03 1.74 ± 3.55 0.71 ± 0.06 0.79 ± 0.05 0.79 ± 0.06 - -Boxer -0.01 ± 0.04 58.63 ± 2.05 0.65 ± 0.02 0.66 ± 0.02 -0.42 ± 2.49 0.57 ± 0.05 0.75 ± 0.04 0.73 ± 0.04 0.43 ± 0.04 0.55 ± 0.05Brittany 0.08 ± 0.08 62.14 ± 4.23 0.66 ± 0.04 0.63 ± 0.03 0.48 ± 3.27 0.69 ± 0.07 - - - -Bulldog -0.11 ± 0.06 46.32 ± 3.00 0.68 ± 0.03 0.64 ± 0.04 4.53 ± 1.85 0.63 ± 0.07 0.68 ± 0.07 0.80 ± 0.05 - -Cairn Terrier -0.11 ± 0.09 53.53 ± 3.84 0.57 ± 0.05 0.67 ± 0.05 - - - - - -Cardigan Welsh Corgi 0.05 ± 0.14 38.83 ± 5.03 - - - - - - - -Cavalier King Charles Spaniel 0.01 ± 0.06 60.24 ± 3.14 0.66 ± 0.02 0.69 ± 0.03 -0.41 ± 3.02 0.56 ± 0.07 0.67 ± 0.08 0.69 ± 0.06 - -Chihuahua -0.01 ± 0.04 42.45 ± 2.34 0.65 ± 0.03 0.59 ± 0.03 -0.01 ± 2.94 0.70 ± 0.06 0.72 ± 0.06 0.77 ± 0.05 0.42 ± 0.06 0.63 ± 0.04Cocker Spaniel -0.01 ± 0.06 58.81 ± 2.97 0.65 ± 0.03 0.66 ± 0.03 2.52 ± 3.13 0.60 ± 0.07 0.79 ± 0.05 0.77 ± 0.05 0.46 ± 0.06 0.67 ± 0.05Collie 0.04 ± 0.08 52.18 ± 4.09 0.61 ± 0.04 0.61 ± 0.04 3.02 ± 3.22 0.69 ± 0.08 - - - -Coton de Tulear 0.11 ± 0.08 54.89 ± 3.86 0.62 ± 0.03 0.60 ± 0.04 0.57 ± 3.92 - - - - -Dachshund 0.01 ± 0.04 55.17 ± 2.10 0.63 ± 0.02 0.62 ± 0.02 3.11 ± 2.87 0.64 ± 0.05 0.79 ± 0.04 0.81 ± 0.04 0.39 ± 0.05 0.58 ± 0.05Dalmatian 0.00 ± 0.09 45.29 ± 5.02 - - - - - - - -Doberman Pinscher 0.04 ± 0.06 51.26 ± 2.72 0.71 ± 0.03 0.66 ± 0.03 1.87 ± 2.76 0.59 ± 0.05 0.66 ± 0.04 0.78 ± 0.04 0.42 ± 0.05 0.52 ± 0.03English Cocker Spaniel -0.17 ± 0.12 63.06 ± 5.24 - - - - - - - -English Springer Spaniel 0.04 ± 0.05 64.22 ± 2.41 0.73 ± 0.03 0.70 ± 0.03 -1.55 ± 2.37 0.62 ± 0.06 0.71 ± 0.05 0.84 ± 0.03 0.42 ± 0.06 0.55 ± 0.05Flat-Coated Retriever -0.09 ± 0.10 64.79 ± 4.16 0.67 ± 0.05 0.66 ± 0.05 - - - - - -French Bulldog -0.01 ± 0.05 50.48 ± 2.80 0.59 ± 0.03 0.64 ± 0.04 1.80 ± 2.07 0.68 ± 0.05 0.78 ± 0.05 0.76 ± 0.05 - -German Shepherd Dog -0.03 ± 0.02 46.60 ± 1.21 0.67 ± 0.01 0.64 ± 0.01 -0.96 ± 1.31 0.68 ± 0.02 0.72 ± 0.02 0.80 ± 0.02 0.51 ± 0.02 0.62 ± 0.02German Shorthaired Pointer -0.05 ± 0.09 46.13 ± 3.53 0.65 ± 0.03 0.62 ± 0.04 - - - - - -Golden Retriever 0.02 ± 0.02 57.57 ± 1.08 0.67 ± 0.01 0.65 ± 0.01 -0.52 ± 1.19 0.62 ± 0.02 0.76 ± 0.02 0.80 ± 0.02 0.44 ± 0.02 0.65 ± 0.02Great Dane -0.02 ± 0.10 45.30 ± 3.56 0.60 ± 0.04 0.60 ± 0.04 - - - - - -Greyhound 0.02 ± 0.06 31.43 ± 3.17 0.56 ± 0.04 0.49 ± 0.03 -4.71 ± 3.60 - - - - -Havanese 0.01 ± 0.06 52.14 ± 2.71 0.66 ± 0.03 0.63 ± 0.03 8.16 ± 3.81 0.72 ± 0.06 0.77 ± 0.05 0.69 ± 0.06 0.40 ± 0.05 -Irish Water Spaniel -0.05 ± 0.06 65.60 ± 2.98 0.72 ± 0.03 0.71 ± 0.03 -0.20 ± 2.91 0.55 ± 0.05 0.63 ± 0.04 0.89 ± 0.03 0.52 ± 0.03 0.68 ± 0.03Italian Greyhound 0.14 ± 0.12 - - - - - - - - -Jack Russell Terrier 0.06 ± 0.05 44.62 ± 3.67 0.61 ± 0.03 0.63 ± 0.04 -1.77 ± 3.55 - - - - -Labrador Retriever 0.04 ± 0.02 55.28 ± 0.83 0.67 ± 0.01 0.64 ± 0.01 -0.92 ± 0.75 0.63 ± 0.02 0.77 ± 0.01 0.81 ± 0.01 0.46 ± 0.01 0.61 ± 0.01Lhasa Apso -0.14 ± 0.10 - - - - - - - - -Maltese 0.07 ± 0.07 45.74 ± 3.26 0.62 ± 0.03 0.62 ± 0.04 - - - - - -Miniature Pinscher 0.00 ± 0.08 51.14 ± 3.67 0.59 ± 0.05 0.67 ± 0.05 5.38 ± 5.34 - - - - -Miniature Poodle 0.03 ± 0.05 56.72 ± 2.84 0.65 ± 0.03 0.64 ± 0.03 5.45 ± 2.87 0.74 ± 0.04 0.81 ± 0.04 0.76 ± 0.05 0.42 ± 0.05 0.58 ± 0.04Miniature Schnauzer 0.01 ± 0.04 51.55 ± 2.23 0.66 ± 0.02 0.66 ± 0.02 -1.69 ± 2.34 0.68 ± 0.05 0.78 ± 0.03 0.85 ± 0.03 0.40 ± 0.04 0.61 ± 0.04Newfoundland -0.12 ± 0.11 50.97 ± 4.88 - - - - - - - -Papillon 0.00 ± 0.07 50.87 ± 4.53 0.67 ± 0.04 0.74 ± 0.05 - - - - - -Parson Russell Terrier 0.14 ± 0.06 53.42 ± 3.96 0.73 ± 0.04 0.69 ± 0.04 - - - - - -Pembroke Welsh Corgi 0.06 ± 0.06 48.83 ± 2.98 0.65 ± 0.03 0.62 ± 0.03 0.89 ± 3.31 0.75 ± 0.05 0.76 ± 0.04 0.79 ± 0.05 0.40 ± 0.05 0.68 ± 0.05Pomeranian 0.02 ± 0.07 51.36 ± 3.82 0.61 ± 0.04 0.65 ± 0.03 8.30 ± 4.40 - - - - -Portuguese Water Dog 0.01 ± 0.07 59.71 ± 2.77 0.64 ± 0.03 0.57 ± 0.03 -1.59 ± 3.33 0.64 ± 0.06 0.73 ± 0.05 0.84 ± 0.05 0.44 ± 0.04 -Pug 0.01 ± 0.05 59.00 ± 2.70 0.67 ± 0.03 0.69 ± 0.03 8.65 ± 3.23 0.63 ± 0.06 0.72 ± 0.04 0.74 ± 0.05 0.51 ± 0.05 0.52 ± 0.06Rat Terrier 0.16 ± 0.07 54.55 ± 4.38 0.69 ± 0.05 0.62 ± 0.06 - - - - - -Rhodesian Ridgeback 0.03 ± 0.06 46.10 ± 3.49 0.68 ± 0.03 0.61 ± 0.04 -1.04 ± 4.72 - - - - -

Rottweiler 0.01 ± 0.08 54.97 ± 3.37 0.65 ± 0.03 0.70 ± 0.03 3.70 ± 3.22 0.69 ± 0.06 0.73 ± 0.07 0.83 ± 0.05 - -Samoyed -0.04 ± 0.13 44.00 ± 5.56 - - - - - - - -Shetland Sheepdog 0.02 ± 0.05 54.05 ± 2.64 0.65 ± 0.02 0.62 ± 0.03 -0.03 ± 2.33 0.70 ± 0.05 0.67 ± 0.04 0.71 ± 0.04 0.51 ± 0.04 0.58 ± 0.03Shiba Inu -0.02 ± 0.06 38.28 ± 3.27 0.57 ± 0.05 0.70 ± 0.04 - - - - - -Shih Tzu -0.04 ± 0.04 45.75 ± 2.40 0.63 ± 0.03 0.62 ± 0.03 5.06 ± 2.57 0.60 ± 0.05 0.64 ± 0.06 0.71 ± 0.06 0.47 ± 0.06 0.51 ± 0.06Siberian Husky 0.09 ± 0.07 41.42 ± 2.68 0.62 ± 0.03 0.64 ± 0.03 0.36 ± 3.24 0.68 ± 0.06 0.79 ± 0.05 0.82 ± 0.05 0.44 ± 0.04 0.54 ± 0.05Soft Coated Wheaten Terrier -0.07 ± 0.07 54.68 ± 3.43 0.61 ± 0.03 0.59 ± 0.04 1.44 ± 4.13 0.68 ± 0.06 0.72 ± 0.05 0.66 ± 0.06 - -St. Bernard 0.00 ± 0.14 53.10 ± 5.57 - - - - - - - -Staffordshire Bull Terrier 0.13 ± 0.11 47.02 ± 4.10 - - - - - - - -Standard Poodle 0.03 ± 0.03 58.64 ± 1.78 0.67 ± 0.02 0.64 ± 0.02 1.77 ± 1.71 0.69 ± 0.03 0.72 ± 0.03 0.78 ± 0.03 0.50 ± 0.03 0.63 ± 0.03Standard Schnauzer 0.00 ± 0.08 50.86 ± 5.49 - - - - - - - -Tibetan Terrier 0.15 ± 0.13 - - - - - - - - -Vizsla 0.12 ± 0.06 59.86 ± 2.93 0.72 ± 0.03 0.61 ± 0.04 4.60 ± 2.76 0.50 ± 0.08 0.75 ± 0.06 0.76 ± 0.06 - -Weimaraner -0.04 ± 0.08 50.07 ± 3.86 0.58 ± 0.03 0.66 ± 0.04 -5.62 ± 4.12 - - - - -West Highland White Terrier 0.04 ± 0.06 43.22 ± 2.89 0.64 ± 0.04 0.62 ± 0.04 3.51 ± 3.96 0.75 ± 0.05 0.65 ± 0.07 0.71 ± 0.06 - -Whippet 0.00 ± 0.10 48.69 ± 3.91 0.67 ± 0.05 0.59 ± 0.05 - - - - - -Yorkshire Terrier 0.09 ± 0.05 49.63 ± 2.66 0.62 ± 0.03 0.65 ± 0.03 4.56 ± 2.75 0.72 ± 0.05 0.69 ± 0.04 0.68 ± 0.05 0.59 ± 0.07 -

Supplementary Table 3. Mean score (± SEM) on each task for all breeds included in the cognitive analyses. Tasks are presented in order conducted from first to last, and are abbreviated as follows: Yawn = Yawning, Eye = Eye Contact, Arm = Arm Pointing, Foot = Foot Pointing, Cunn = Cunning, MvP = Memory vs. Pointing, MvS = Memory vs. Smell, Mem = Delayed Memory, IR = Inferential Reasoning, and PR = Physical Reasoning. Scores on each task were calculated as follows: Yawn = Binary measure (at least one yawn or no yawns) in test condition minus control condition; Eye = Duration of eye contact in seconds; Arm and Foot = Proportion of gesture follows; Cunn = Seconds to take food in the Watching condition minus the Not Watching condition; MvP and MvS = Proportion of searches to remembered location; Mem, IR, and PR = Proportion of successful searches.

Supplementary Table 4

Task n β χ2 pYawning 7285 -0.00014 0.13 0.72Eye Contact 6448 0.017 0.12 0.73Arm Pointing 4510 0.00068 6.51 0.011*Foot Pointing 4215 0.00004 0.02 0.89Cunning 3045 -0.080 13.40 <0.001* Watching Condition 3046 0.27 10.25 0.001* Not Watching Condition 3097 0.33 15.34 <0.001*Memory vs. Pointing 2548 -0.0011 3.64 0.056Memory vs. Smell 2390 0.00010 0.05 0.83Delayed Memory 2310 0.0015 11.06 <0.001*Inferential Reasoning 1924 0.00084 3.70 0.054Physical Reasoning 1852 0.00092 4.00 0.045*

Supplementary Table 4. Results from mixed linear models (controlling for breed-level genetic relatedness) predicting cognitive performance from breed-average estimated brain weight for each task on an individual level. Significant p-values are denoted in bold.

Supplementary Table 5

Task β χ2 pYawning -0.00072 1.37 0.24Eye Contact -0.043 0.44 0.51Arm Pointing 0.00083 3.35 0.07Foot Pointing -0.00014 0.09 0.78Cunning -0.14 10.77 0.001* Watching Condition 0.49 10.78 0.001* Not Watching Condition 0.63 18.21 <0.001*Memory vs. Pointing -0.002 3.67 0.06Memory vs. Smell -0.0005 0.35 0.56Delayed Memory 0.0028 12.10 <0.001*Inferential Reasoning 0.0003 0.10 0.75Physical Reasoning 0.00048 0.18 0.67Supplementary Table 5. Results from mixed linear models (controlling for genetic relatedness) predicting cognitive performance from CBARQ-reported breed-average body weight for each task within the same sample as our main breed-level analyses (Table 1). Significant p-values are denoted in bold.

Supplementary Figure 1

Supplementary Figure 1. Plot of log10 transformed C-BARQ breed-average body weights (in kilograms) and brain weights (in grams) reported in Bronson (1979) for 24 breeds with a linear model predicting brain weight from body weight overlaid.

Supplementary Figure 2

Supplementary Figure 2. Scores on all cognitive tasks a function of CBARQ-reported breed-average body weight across dog breeds. The dashed lines show the regression slopes from statistical models controlling for genetic relatedness between breeds. Each breed included in the analyses had at least 20 individuals complete a given task, and is represented by one diamond.

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