DOI: 10.5061/dryad.kh18932b2
title: Data from: Prosociality in a despotic society

description: Prosociality is the intent to improve others’ well-being. Existing
 hypotheses postulate that enhanced social tolerance and inter-individual
 dependence may facilitate prosocial preferences, which may favor the
 evolution of altruism. While most studies are restricted to ‘tolerant’
 (cooperatively breeding and self-domesticated) species, despotic societies
 provide an alternative opportunity to investigate prosociality due to
 nepotism and ample inter-individual dependencies. Japanese macaques live
 in hierarchical matrilineal societies, with strong kin bonds. Besides,
 tolerance among non-kin may persist through reciprocity. Using a group
 service food-provision paradigm, we found prosocial preferences in a semi
 free-ranging group of Japanese macaques. The extent of provisioning was at
 levels comparable to tolerant species. Dyadic tolerance predicted the
 likelihood and magnitude of provisioning, while kinship predicted the
 magnitude. We emphasize the role of a complex socio-ecology fostering
 individual prosocial tendencies through kinship and tolerance. These
 findings necessitate a framework including different forms of
 interdependence beyond the generally tolerant species.
description: <strong>(a) Study site
 and subjects</strong>: The study was conducted with a semi-free-ranging
 group (~170 individuals) of Japanese macaques at Affenberg Landskron in
 Austria from February to May 2022. The macaques live in natural
 socio-environmental conditions with limited human intervention, except for
 feeding and emergency medical purposes (such as veterinary care). However,
 the group is habituated to human presence as visitors can enter the
 enclosure within the scope of guided tours offered by the park from April
 to September. Our study gained high ecological validity due to the
 population's living conditions and naturalistic group
 setting. A total of 25
 self-trained individuals voluntarily participated in the study while
 remaining in their social group. Direct interaction between the subjects
 and the experimenter was avoided by placing the apparatuses needed for our
 experiments in small research huts (with wire mesh separations), which the
 macaques could operate from outside. Affenberg Landskron provided age,
 sex, and rank data (see raw data sheet “large”) of the individuals as
 long-term behavioural observations were being conducted for other studies
 with the population. <strong>(b) Apparatuses</strong>:
 We used a seesaw mechanism
 for the group service paradigm (Burkart and van Schaik, 2013; Horn et al.,
 2020), whereas a string-pulling task was conducted to measure dyadic
 social tolerance (Massen et al., 2015). The seesaw tool used a wooden
 board (length ~ 1.5 m) attached to the grids of the wire mesh separation
 of a research hut. The wooden board had two transparent plastic pipes (Ø ~
 3 inches) attached to two extremes (pos 0 and pos 1) through which food
 rewards (i.e., peanuts) could move. By default, the board was tilted
 towards the experimenter. A metal handle was connected to one of the ends
 of the board (pos 0) and projected outside, which upon pressing, could
 tilt the board towards the macaques, resulting in food rolling down
 through the pipe(s) (if present). In an attempt to press or when an
 individual released the handle halfway, the seesaw moved back to its
 original position, and the food (if present) would role out of reach
 again. Therefore, it was essential to press fully and hold the handle to
 get the food rewards. For the
 string-pulling (dyadic tolerance) task, we used a wooden platform (length
 ~ 1.5 m) to which two strings were attached at the two extremes. Food
 rewards were placed out of reach of the macaques on two ends of the
 platform, which could only be moved by pulling one of the strings. The
 task required no joint action. The length of the apparatuses was kept
 constant. <strong>(c) Experimental Procedure:
 </strong> <strong>(i) Group service
 paradigm</strong> – The protocol consisted of several phases:
 habituation to the apparatus, social tolerance phase, apparatus training,
 group service (test and empty control), and blocked controls in a
 pre-determined order (see below). Each phase served a purpose and came
 with a criterion that needed to be fulfilled to begin the next phase. The
 rewards used were peanuts. 
 <strong><em>Phase
 0 (Habituation phase)</em></strong>
 This phase was carried out to
 reduce and/or eliminate any potential neophobia towards the seesaw
 apparatus and to habituate individuals to the setup. Food items were
 spread over the wooden board at regular intervals. The experimenter tried
 to catch the attention of the individuals by calling “Monkeys”. Three
 sessions were conducted (each on one day for ~1 hour). A total of 25
 individuals participated in this phase voluntarily and obtained food
 rewards successfully.
 <strong><em>Phase
 1 (Initial training and habituation to
 procedure)</em></strong>
 The mechanism of the seesaw
 was completely locked, and the platform was tilted towards the
 individuals. So, when placed in either position, food rewards would roll
 down to the individuals. We conducted a total of five sessions, and for
 each session,  food was provided in pos. 0 and pos. 1, alternately. The
 number of trials was determined according to the number of individuals who
 successfully passed phase 0 (25 * 5 = 125 trials/session, see (Horn et
 al., 2016)). This number was used for the following phases as well. A
 trial began when a food reward was placed (either in Pos. 0 or Pos. 1) and
 ended with an individual retrieving it or after 2 min. In this phase, an
 individual was considered trained if they received at least a total of 10
 rewards throughout the different sessions. To fulfil the criterion, at
 least half of the habituated individuals needed to get trained. We
 recorded which individual(s) obtained the rewards for each
 trial. <strong><em>Phase 2 (Social tolerance
 test)</em></strong> The procedure was the same as in phase 1, with
 the mechanism still locked and the platform tilted toward the individuals.
 However, food rewards were always placed in Pos. 1 in this phase. We
 conducted two sessions, with each having 125 trials.
 <strong><em>Phase 3 (Apparatus
 training)</em></strong>
 The seesaw mechanism was
 operational from this phase and onwards. Therefore, individuals needed to
 learn to press the handle to tilt the board and get the rewards. Food
 rewards were always placed in Pos. 0. Thus, individuals pressing and
 holding the handle could make food rewards available to themselves. The
 phase was completed when at least half of the individuals obtained at
 least ten rewards over five sessions. 
 <strong><em>Phase
 4 (group service: test and empty
 control)</em></strong>
 This phase was the core of the
 experiment. In test sessions, food was placed in Pos. 1 for each of the
 125 trials of the test sessions. An individual needed to press the handle
 in Pos. 0 to make food accessible for another individual in Pos.1. The
 trial began when the experimenter placed a peanut in the pipe in Pos. 1
 while drawing the attention of the macaques (by calling “Monkeys”). An
 actor could provision by pressing and holding the handle within a maximum
 duration of 2 min. If not, the experimenter removed the reward from the
 pipe and started a new trial. Trials were conducted at different times
 throughout the day, from 0930 to 1830 hours. We carried out empty control
 sessions alternately with the test sessions. Here, the experimenter
 pretended to put a reward in Pos. 1 but left the pipe empty to check for
 potential stimulus enhancement effects. The maximum duration of a trial
 was again 2 min. 
 <strong><em>Phase
 5 (Blocked controls)</em></strong>
 The access to the food pipe in
 Pos. 1 was blocked by attaching plexiglass to the enclosure. Food reward
 was thus visible but not accessible to the individuals, even if actors
 pressed the handle. We conducted five blocked test sessions during which
 food was placed in Pos. 1 (similarly to test sessions in phase 4),
 alternately with five empty (blocked) control sessions (no food placed in
 Pos. 1). <strong><em>Phase 6 (Re-test and empty
 controls)</em></strong>
 To check for any potential
 bias due to the experimental order (Horn et al., 2016; Thornton and
 McAuliffe, 2015), we repeated two tests and two empty control sessions.
 The procedure was exactly the same as the regular test and empty control
 sessions. We recorded the identities of the individuals
 pressing, provisioning, and receiving for all the above phases (wherever
 applicable). Also, we measured the latencies for pressing the handle for
 all the trials. For phases 4, 5 and 6, every fifth trial was a motivation
 trial. Food was placed in Pos. 0, accessible to the actor (if pressed).
 These motivation trials kept the monkeys interested in participating in
 the experiment. Additionally, these trials helped check if low pressing
 rates (if any) resulted from a general lack of willingness to participate
 in the experiment. <strong>(ii) String-pulling (dyadic tolerance)
 task </strong>– The
 string-pulling task was designed to assess dyadic social tolerance. This
 task was independent of the group service paradigm and was performed
 afterwards. 
 <strong><em>Habituation to
 apparatus</em></strong>
 We first conducted a
 habituation phase for a whole day (between 0930 and 1830 hours). We put
 food rewards on the platform and moved it slowly toward the monkeys. This
 phase aimed to familiarize the monkeys with the apparatus. Individuals
 were considered habituated after obtaining at least five rewards during
 the habituation phase.
 <strong><em>Dyadic
 social tolerance</em></strong> 
 The experiment lasted three
 days, and we conducted 18 sessions of 20 trials each. Every trial began by
 calling “Monkeys” while placing food rewards (peanuts) on either end of
 the platform yet out of reach of the monkeys. Once the monkeys were
 attentive, we presented both strings at the same time. To access the
 rewards, at least one individual needed to pull. The trial ended when the
 platform was moved and rewards obtained or after 2 min. When the platform
 was moved, two pieces of food rewards were accessible, placed ~1 m apart,
 meaning that a high social tolerance was necessary for two individuals to
 retrieve the rewards simultaneously. Thus, monopolization of both rewards
 by a single individual was also possible. 
 We recorded all the
 phases of the two experiments using a Canon Legria HF G86 video camera
 mounted on a tripod. Additionally, we noted the identities of the
 individuals participating using a pen and a
 notebook. 
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