DOI: 10.5061/dryad.6q573n60g
title: High pitch sounds small for domestic dogs dataset

description: Humans possess intuitive associations linking certain non-redundant
 features of stimuli – e.g., high-pitched sounds with small object-size (or
 similarly, low-pitched sounds with large object-size). This phenomenon,
 known as crossmodal correspondence, has been identified in humans across
 multiple different senses. There is some evidence that non-human animals
 also form crossmodal correspondences, but the known examples are mostly
 limited to the associations between the pitch of vocalisations and the
 size of callers. To investigate whether domestic dogs, like humans, show
 abstract pitch-size association, we first trained dogs to approach and
 touch an object after hearing a sound emanating from it. Subsequently, we
 repeated the task but presented dogs with two objects differing in size,
 only one of which was playing a sound. The sound was either high- or
 low-pitched, thereby creating trials that were either congruent
 (high-pitch from small object; low-pitch from large objects) or
 incongruent (the reverse). We found that dogs reacted faster on congruent
 versus incongruent trials. Moreover, their accuracy was at chance on
 incongruent trials, but significantly above chance for congruent trials.
 Our results suggest that non-human animals show abstract pitch-sound
 correspondences, indicating these correspondences may not be uniquely
 human but rather a sensory processing feature shared by other species.
description: <b>Participants</b> Fifty domestic
 dogs of unrestricted breeds aged between 6 and 132 months (M=56.1,
 SD=36.6) were recruited through social media advertisements and word of
 mouth. We removed dogs who failed to complete training (n=8), or who
 failed to produce any useable testing trials (n=12; e.g., they were too
 distracted to perform the task). Further 111 trials from the remaining
 dogs were also removed (e.g., due to background noise, or owner
 interference; see Electronic Supplementary Material (ESM) for full
 exclusion criteria). This left 133 trials from 30 dogs.
 <b>Materials</b> The training
 stimulus consisted of a plastic-coated 3-dimensional frustum-shaped
 object, painted blue to increase visual salience for the dogs. The frustum
 had a base-diameter of 29cm and a volume of approximately 9000
 cm<sup>3</sup>. A JBL Flip 4 Bluetooth speaker was inserted
 via a small hole in the side of the object and the remaining cavity filled
 with insulating rockwool (Knauf Earthwool) to reduce any resonances from
 the speaker. The sound stimulus for training was a 2-second-long 430Hz
 (9.33 erb) pure tone created in PRAAT. The sound was played at 86dB
 (approximately 65dB measured at the dog’s position) which was controlled
 from a Motorola Razor phone connected to the speaker via Bluetooth. The
 dogs’ behaviour was recorded using 3 cameras: a Go Pro Hero 7 camera
 positioned on the right side of the dog; a GoPro Max camera positioned to
 the front of the dog, and a Sony Handycam camera positioned to the right
 (or left, depending on the position of the experimenter) and behind the
 dog. Additionally, there was a Sony Handycam camera, positioned in front
 of the dog, to the right or left of a partition screen which was hiding
 the experimenter. This was connected to an Acer LED 21.5” Monitor
 (KA220HQ) where the experimenter could watch the behaviour of the dog
 while out of sight. The testing stimuli were identical
 to training stimuli in all ways other than the following: There were now
 <i>two</i> objects per trial, one big and one small
 (approximately 23000cm<sup>3</sup> and
 2300cm<sup>3</sup> respectively). To ensure that our findings
 would hold across multiple shapes, we created three sets of objects: a
 pair of cylinders, a pair of cones, and a pair of cuboids – ensuring each
 dog saw one set only (e.g., a big and small cuboid). There were now also
 two sound stimuli, one low pitch (150Hz, 4.26 erb) and one high pitch
 (900Hz, 14.4 erb). All other aspects of stimuli and recordings were as in
 the training phase. Remaining materials were a partition screen,
 button-clicker, reward-tube, and rewards. The experimenter trained the
 dogs to touch the object using a button clicker and commercially available
 dog treats (see below). Treats were delivered via the plastic reward-tube
 attached to the partition screen, whose position and orientation is
 described below. <b>Training</b>
 Dogs were brought into the testing room at the University of
 Sussex by their owners and given approximately 5 minutes to acclimatise,
 while owners signed the consent form and completed a questionnaire about
 their dogs (stating their breed, age, sex, neuter status, and weight).
 Then the owners were asked to sit in a chair facing a partition screen,
 which had a reward-tube attached to it. Each dog was put into a “sit”
 position directly in front of the owner to prevent the owner from
 accidentally cueing the dog, and owners were asked not to interact with
 their dogs during the experiment. Between the dog and the screen was the
 training object. When training began, the experimenter
 used “shaping” with the aid of a clicker to train the dogs to target the
 training object with their nose or paw. This technique involves waiting
 for the desired  behaviour and quickly marking and
 rewarding when it occurs. This method was chosen to avoid additional
 prompts or social cues that would later have to be faded, which could
 prolong the training process. The primary reinforcer (food treat) was
 delivered through a reward-tube attached to the screen positioned behind
 the object (facing the dog). The screen itself also served a purpose of
 allowing the experimenter to hide behind it during testing to avoid
 influencing the dogs’ behaviour. After a correct response was established
 (i.e., dog consistently targeting the object and touching with nose or
 paw), a sound playing from the speaker within the object was now
 introduced. If the dog moved too soon (before the sound was played) the
 experimenter prevented the dog from touching the object, by blocking it
 with her hand or lifting the object up. After each repetition of the
 behaviour, the dog was returned to the “sit” position in front of the
 owner and another trial was initiated. As the training progressed, the
 owner and dog were slowly moved backwards to increase the distance the dog
 had to travel to touch the object, and the experimenter started to
 gradually retreat behind the room-dividing screen. Training continued
 until the owner’s chair was in position by the wall opposite the screen
 (350cm away from the screen) <i>and</i> the dog was able to
 sit and wait in an appropriate position for the next sound to be played by
 the experimenter (now hidden out of view behind the screen). The
 appropriate position for the dog was to be seated in front of the owner
 but behind an orange line drawn on the floor. A final 6 trials (object to
 the left of the dog x2, object to the right of the dog x2, object in the
 middle x2) had to be completed with 100% accuracy before training ended
 and the experiment moved on to the testing phase. If this failed, another
 block of 6 training trials was completed.
 <b>Testing</b> Testing took place
 immediately after successful training was complete, and the dog and owner
 remained in the position they had reached at the end of training. All
 elements of testing were identical to training except now two objects were
 used, again placed in front of the screen, one to the left and one to the
 right, equidistant from the reward delivery tube, 90cm in front of the
 screen, 124 cm away from each other, and 150cm away from the dog. The
 shape of the objects was randomly assigned to each dog (i.e., a pair of
 cylinders or cones or cuboids). Only one of the objects played a sound on
 each trial. Dogs were presented with 8 trials in total, crossing the three
 variables shown in Table 1. This crossing effectively means every trial
 presented two objects (big and small) one of which was playing a sound
 (high or low pitched), with objects switching on the left or right of the
 space (e.g., Trial 1 big-on-left; Trial 2 big-on-right). The presentation
 of two objects and two sounds was necessary because the pitch-size
 correspondence appears to be relative in humans, rather than absolute. In
 other words, we hypothesised that dogs must see two objects to know that
 one is ‘big’ and must hear two sounds to know that one is ‘high’. As with
 training, each trial began with the experimenter positioning the stimuli
 (i.e., moving the small/big objects left/right, according to the trial
 type) and setting the dog up in a sitting position in front of (and facing
 away from) its owner. The experimenter then retreated behind the screen,
 from where she could manipulate the sound media. She then activated the
 sound, which was the signal for the dog to approach and touch the
 sound-making object. When the dog touched the object, the experimenter
 marked the behaviour with a click from the clicker and deposited a small
 treat via the tube as a reward for the dog. The dog was then repositioned
 by the experimenter in preparation for the next trial. If the dog did not
 respond at all within 40s from start of the sound stimulus, the sound was
 repeated. If the dog continued to not respond, the trial was recorded as
 “no response”, and the next trial began. If the dog moved out of position,
 but made no choice (e.g., went to investigate an area of the testing room
 where there was no object) this was also recorded as “no response”. If the
 dog showed signs of stress such as excessive panting, pacing,
 comfort-seeking from owner, excessive whimpering, or avoidance of the
 experimenter, the experiment was terminated.
 <b>Design</b> Of each dog’s eight
 trials, four were congruent (small object playing high pitch sound; or big
 object playing low pitch sound; once with small object on the left and
 once with small object on the right). The remaining four trials were
 incongruent (i.e., small/low on left and right, and big/high on left and
 right). The combination of trials was pseudo-randomly assigned to each
 dog, to avoid any ordering effect. <b>Video
 coding</b> Video recordings of dog behaviour were
 edited in iMovie (Apple Inc.) to replace the sound stimulus for each trial
 with a ringing tone to allow the behaviour of the dogs to be coded blind.
 Subsequently, the recordings were analysed using SportsCode Gamebreaker
 version 10 by ATK, and 25% of trials by HRG.