Towards integrating joint action research: Developmental and evolutionary perspectives on co-representation.

Joint action has increasingly become a key topic to understand the emergence of the human mind. The phenomenon is closely linked to several theoretical concepts, such as shared intentionality, which are difficult to operationalize empirically. We therefore employ a paradigm-driven, bottom-up approach, and as such discuss co-representing the partner's and one's own actions as key mechanism for joint action. After embedding co-representation in the broader landscape of related theoretical concepts, we review neurobiological, ontogenetic, and phylogenetic studies, with a focus on whether co-representation and its flexible deployment should be construed as a low- or high-level cognitive process. The empirical findings convergently suggest that co-representation does not require strong inhibitory skills or mentalistic understanding and occurs automatically. Moreover, more cooperative species are better at flexibly suppressing co-representation when required for cooperation success, and frequently rely on cooperation markers, such as mutual gaze. We thus contribute to closing the current gap between theoretical concepts related to joint action research and their empirical investigation, and end by highlighting additional approaches for doing so.

A convergent interaction engine: vocal communication among marmoset monkeys.

To understand the primate origins of the human interaction engine, it is worthwhile to focus not only on great apes but also on callitrichid monkeys (marmosets and tamarins). Like humans, but unlike great apes, callitrichids are cooperative breeders, and thus habitually engage in coordinated joint actions, for instance when an infant is handed over from one group member to another. We first explore the hypothesis that these habitual cooperative interactions, the marmoset interactional ethology, are supported by the same key elements as found in the human interaction engine: mutual gaze (during joint action), turn-taking, volubility, as well as group-wide prosociality and trust. Marmosets show clear evidence of these features. We next examine the prediction that, if such an interaction engine can indeed give rise to more flexible communication, callitrichids may also possess elaborate communicative skills. A review of marmoset vocal communication confirms unusual abilities in these small primates: high volubility and large vocal repertoires, vocal learning and babbling in immatures, and voluntary usage and control. We end by discussing how the adoption of cooperative breeding during human evolution may have catalysed language evolution by adding these convergent consequences to the great ape-like cognitive system of our hominin ancestors. This article is part of the theme issue 'Revisiting the human 'interaction engine': comparative approaches to social action coordination'.

Trade-offs between vocal accommodation and individual recognisability in common marmoset vocalizations.

Recent studies find increasing evidence for vocal accommodation in nonhuman primates, indicating that this form of vocal learning is more prevalent than previously thought. Convergent vocal accommodation (i.e. becoming more similar to partners) indicates social closeness. At the same time, however, becoming too similar may compromise individual recognisability. This is especially problematic if individual recognisability is an important part of the call function, like in long-distance contact calls. In contrast, in calls with a different function, the trade-off between signalling social closeness and individual recognisability might be less severe. We therefore hypothesized that the extent and consequences of accommodation depend on the function of a given call, and expected (1) more accommodation in calls for which individual identity is less crucial and (2) that individual identity is less compromised in calls that serve mainly to transmit identity compared to calls where individual recognisability is less important. We quantified vocal accommodation in three call types over the process of pair formation in common marmoset monkeys (Callithrix jacchus, n = 20). These three call types have different functions and vary with the degree to which they refer to individual identity of the caller. In accordance with our predictions, we found that animals converged most in close contact calls (trill calls), but less in calls where individual identity is more essential (phee- and food calls). In two out of three call types, the amount of accommodation was predicted by the initial vocal distance. Moreover, accommodation led to a drop in statistical individual recognisability in trill calls, but not in phee calls and food calls. Overall, our study shows that patterns of vocal accommodation vary between call types with different functions, suggestive of trade-offs between signalling social closeness and individual recognisability in marmoset vocalizations.

Do marmosets understand others' conversations? A thermography approach.

What information animals derive from eavesdropping on interactions between conspecifics, and whether they assign value to it, is difficult to assess because overt behavioral reactions are often lacking. An inside perspective of how observers perceive and process such interactions is thus paramount. Here, we investigate what happens in the mind of marmoset monkeys when they hear playbacks of positive or negative third-party vocal interactions, by combining thermography to assess physiological reactions and behavioral preference measures. The physiological reactions show that playbacks were perceived and processed holistically as interactions rather than as the sum of the separate elements. Subsequently, the animals preferred those individuals who had been simulated to engage in positive, cooperative vocal interactions during the playbacks. By using thermography to disentangle the mechanics of marmoset sociality, we thus find that marmosets eavesdrop on and socially evaluate vocal exchanges and use this information to distinguish between cooperative and noncooperative conspecifics.

The use of infrared thermography to investigate emotions in common marmosets.

Measuring body surface temperature changes with infrared thermography has recently been put forward as a non-invasive alternative measure of physiological correlates of emotional reactions. In particular, the nasal region seems to be highly sensitive to emotional reactions. Several studies suggest that nasal temperature is negatively correlated with the level of arousal in humans and other primates, but some studies provide inconsistent results. Our goal was to establish the use of infrared thermography to quantify emotional reactions in common marmosets (Callithrix jacchus), with a focus on the nasal region. To do so we exposed 17 common marmosets to a set of positive, negative and control stimuli (positive: preferred food, playback of food calls; negative: playback of aggressive vocalizations, teasing; control: no stimulus). We compared nasal temperature before and after the stimuli and expected that highly aroused emotional states would lead to a drop in nasal temperature. To validate the thermography measure, we coded piloerection of the tail as an independent measure of arousal and expected a negative correlation between the two measures. Finally, we coded physical activity to exclude its potential confounding impact on nasal temperature. Our results show that all predictions were met: the animals showed a strong decrease in nasal temperature after the presentation of negative arousing stimuli (teasing, playback of aggressive vocalizations). Furthermore, these changes in nasal temperature were correlated with piloerection of the tail and could not be explained by changes in physical activity. In the positive and the control conditions, we found systematic sex differences: in males, the preferred food, the playbacks of food calls, as well as the control stimulus led to an increase in nasal temperature, whereas in females the temperature remained stable (preferred food, control) or decreased (playback of food calls). Based on naturalistic observations that document higher food motivation and competition among female marmosets, as well as stronger reactions to separation from group members in male marmosets, these sex differences corroborate a negative correlation between arousal and nasal temperature. Overall, our results support that measuring nasal temperature by infrared thermography is a promising method to quantify emotional arousal in common marmosets in a fully non-invasive and highly objective way.

Reverse audience effects on helping in cooperatively breeding marmoset monkeys.

Cooperatively breeding common marmosets show substantial variation in the amount of help they provide. Pay-to-stay and social prestige models of helping attribute this variation to audience effects, i.e. that individuals help more if group members can witness their interactions with immatures, whereas models of kin selection, group augmentation or those stressing the need to gain parenting experience do not predict any audience effects. We quantified the readiness of adult marmosets to share food in the presence or absence of other group members. Contrary to both predictions, we found a reverse audience effect on food-sharing behaviour: marmosets would systematically share more food with immatures when no audience was present. Thus, helping in common marmosets, at least in related family groups, does not support the pay-to-stay or the social prestige model, and helpers do not take advantage of the opportunity to engage in reputation management. Rather, the results appear to reflect a genuine concern for the immatures' well-being, which seems particularly strong when solely responsible for the immatures.

The evolutionary origin of human hyper-cooperation.

Proactive, that is, unsolicited, prosociality is a key component of our hyper-cooperation, which in turn has enabled the emergence of various uniquely human traits, including complex cognition, morality and cumulative culture and technology. However, the evolutionary foundation of the human prosocial sentiment remains poorly understood, largely because primate data from numerous, often incommensurable testing paradigms do not provide an adequate basis for formal tests of the various functional hypotheses. We therefore present the results of standardized prosociality experiments in 24 groups of 15 primate species, including humans. Extensive allomaternal care is by far the best predictor of interspecific variation in proactive prosociality. Proactive prosocial motivations therefore systematically arise whenever selection favours the evolution of cooperative breeding. Because the human data fit this general primate pattern, the adoption of cooperative breeding by our hominin ancestors also provides the most parsimonious explanation for the origin of human hyper-cooperation.

Adequacy of peritoneal dialysis.

The National Kidney Foundation-Dialysis Outcomes Quality Initiatives guidelines have standardized many aspects of treating end-stage renal disease patients with peritoneal dialysis in an attempt to improve overall patient outcome. While recommending certain total solute clearance goals, the guidelines have also pointed out deficiencies in our knowledge base and precipitated many controversies. Some of these controversies have been resolved while others may have been interpreted wrongly, unnecessarily resulting in transfer of patients from peritoneal dialysis to hemodialysis due to "failure to meet adequacy targets" even when doing well clinically. This report reviews the rationale for the original guidelines and their subsequent modification. It also outlines a rational approach toward prescription modification based on peritoneal physiology. Specific solute clearance target goals discussed are the modifications for continuous ambulatory peritoneal dialysis (CAPD) and cycler peritoneal dialysis (CCPD), and a review of what solute clearance targets subsequent guidelines from other countries have used. Some examples are as follows: new guidelines suggest that solute clearance goals for creatine clearance should differ for low and low-average transporters than for high and high-average transporters (weekly clearance of 50 and 60 1/1.73 m(2), respectively) while Kt/V targets remain unchanged. Also discussed is the rationale for having the same target for patients on CCPD with a mid-day exchange as those for patients on CAPD. We are also reminded that solute clearance is only one aspect of "adequate" dialysis-blood pressure and volume control are equally important, and ways to maintain euvolemia and blood pressure control are discussed in the context of prescription management.

Incremental initiation of dialysis: one center's experience over a two-year period.

OBJECTIVE: This pilot study describes our center's experience with peritoneal dialysis (PD) over the past 2 years using a "healthy start" dialysis protocol with an incremental approach to prescription management. DESIGN: Nonrandomized, prospective pilot study. SETTING: Single PD unit of a university teaching hospital. PATIENTS: Thirteen PD patients who initiated dialysis at our center from April 1997 to June 1999. METHODS: Patients initiating PD with residual renal Kt/V of 1.0 - 2.0/week were invited to participate. They were given an initial dialysis prescription so that total (residual renal + dialysis) weekly Kt/V exceeded 2.0. The dialysis prescription was "incrementally" increased as residual renal function (RRF) declined. Data collected for all patients included monthly serum chemistries, residual renal weekly Kt/V and creatinine clearance (CCr) at 1- to 2-month intervals, and peritoneal weekly Kt/V and CCr at 3-month intervals and 1 month after each prescription change. RESULTS: To date, we have followed 13 patients on our incremental PD protocol for a total of 159.3 patient-months. Mean serum albumin concentration and mean normalized protein equivalent of nitrogen appearance (nPNA) were stable throughout the study. Mean total Kt/V and CCr remained above the recommended targets of 2.0/wk and 60 L/wk, respectively. Residual renal function declined rather slowly in our PD patients. One patient died from complications of aortic valve surgery and a second died from pneumonia. A third patient died from peritonitis. One patient required a new Tenckhoff catheter after catheter migration. Three patients were temporarily switched to hemodialysis after a hernia repair, a pleural leak, and elective native/transplant nephrectomies, respectively. Two patients were permanently switched to hemodialysis: one after an episode of peritonitis, the second after accidentally damaging his PD catheter. CONCLUSIONS: Providing incremental dialysis to maintain adequate total small solute clearance has been technically feasible in our patient population. However, a larger than expected number of complications was seen in our study. Fortunately, complications were easier to manage due to the presence of RRF. Because this study was not designed to compare outcome with that observed after traditional initiation of dialysis, further large-scale studies are needed.

A multicenter study of noncompliance with continuous ambulatory peritoneal dialysis exchanges in US and Canadian patients.

Recent evidence suggested that noncompliance (NC) with continuous ambulatory peritoneal dialysis (CAPD) exchanges may be more common in US than in Canadian dialysis centers. This issue was investigated using a questionnaire-based method in 656 CAPD patients at 14 centers in the United States and Canada. NC was defined as missing more than one exchange per week or more than two exchanges per month. Patients were ensured of the confidentiality of their individual results. Mean patient age was 56 +/- 16 years, 52% were women, and 39% had diabetes. The overall admitted rate of NC was 13%, with a rate of 18% in the United States and 7% in Canada (P < 0.001). NC was more common in younger patients (P < 0.0001), those without diabetes (P < 0.001), and employed patients (P < 0.05). It was also more common in black and Hispanic than in Asian and white patients (P < 0.001). NC was more common in patients prescribed more than four exchanges daily (P < 0.0001) but was not affected by dwell volume. On multiple regression analysis, the independent predictors of NC, in order of importance, were being prescribed more than four exchanges per day, black race, being employed, younger age, and not having diabetes. Being treated in a US unit did not quite achieve significance as a multivariate independent predictor. These findings suggest that NC is not uncommon in CAPD patients and is more frequent in US than in Canadian patients. However, country of residence is less powerful as a predictor of NC than a variety of other demographic and prescription factors.

Measurement of continuous ambulatory peritoneal dialysis prescription adherence using a novel approach.

OBJECTIVE: The purpose of the study was to test a novel approach to monitoring the adherence of continuous ambulatory peritoneal dialysis (CAPD) patients to their dialysis prescription. DESIGN: A descriptive observational study was done in which exchange behaviors were monitored over a 2-week period of time. SETTING: Patients were recruited from an outpatient dialysis center. PARTICIPANTS: A convenience sample of patients undergoing CAPD at Piedmont Dialysis Center in Winston-Salem, North Carolina was recruited for the study. Of 31 CAPD patients, 20 (64.5%) agreed to participate. MEASURES: Adherence of CAPD patients to their dialysis prescription was monitored using daily logs and an electronic monitoring device (the Medication Event Monitoring System, or MEMS; APREX, Menlo Park, California, U.S.A.). Patients recorded in their logs their exchange activities during the 2-week observation period. Concurrently, patients were instructed to deposit the pull tab from their dialysate bag into a MEMS bottle immediately after performing each exchange. The MEMS bottle was closed with a cap containing a computer chip that recorded the date and time each time the bottle was opened. RESULTS: One individual's MEMS device malfunctioned and thus the data presented in this report are based upon the remaining 19 patients. A significant discrepancy was found between log data and MEMS data, with MEMS data indicating a greater number and percentage of missed exchanges. MEMS data indicated that some patients concentrated their exchange activities during the day, with shortened dwell times between exchanges. Three indices were developed for this study: a measure of the average time spent in noncompliance, and indices of consistency in the timing of exchanges within and between days. Patients who were defined as consistent had lower scores on the noncompliance index compared to patients defined as inconsistent (p = 0.015). CONCLUSIONS: This study describes a methodology that may be useful in assessing adherence to the peritoneal dialysis regimen. Of particular significance is the ability to assess the timing of exchanges over the course of a day. Clinical implications are limited due to issues of data reliability and validity, the short-term nature of the study, the small sample, and the fact that clinical outcomes were not considered in this methodology study. Additional research is needed to further develop this data-collection approach.

Frequency and causes of discrepancy between Kt/V and creatinine clearance.

UNLABELLED: This study examines the frequency of discrepancy between Kt/V urea and creatinine clearance (Ccr) measurements in patients on peritoneal dialysis (PD) and the reasons for this discrepancy. DESIGN: Nonrandomized, retrospective data analysis. SETTING: Single PD unit of a university teaching hospital. PATIENTS: All adult patients receiving PD at our center from January 1995 to December 1996. METHODS: Actual (a) and desired (d) body weight (BW) were used to calculate urea volume of distribution (V) and body surface area (BSA). Patients were divided into four groups based upon their total small solute clearances (Kt/V and Ccr, normalized by actual weight) and three additional groups based upon actual/desired (a/d) body weight ratio. An additional analysis was performed for the subset of anuric patients. Data collected for all patients included the following: total Kt, total Ccr, 4-hour dialysate/ plasma (D/P) creatinine, serum albumin concentration, duration of PD, actual body weight, age, and height. RESULTS: Twenty-three percent of the clearance measurements in our study were discrepant, defined as having values for either Kt/V or Ccr (but not both) above the accepted targets of Kt/V > or = 2.0/wk and Ccr > or = 60 L/wk/ 1.73 m2. Patients with both values above target are more likely to have higher residual renal function. Patients who are significantly less than BWd and patients on PD for a longer time are more likely to have adequate Kt/V but not Ccr. Furthermore, patients who are less than 90% or greater than 110% of BWd have markedly different values for Kt/V and Ccr when BWa versus BWd values are used. CONCLUSIONS: Kt/V and Ccr values are frequently discrepant; a number of factors affect these two measurements to varying degrees, including weight, degree of residual renal function, and duration of PD.

An international study of patient compliance with hemodialysis.

CONTEXT: International differences in compliance of patients undergoing hemodialysis are poorly characterized and could contribute to international survival differences. OBJECTIVE: To compare international differences in patient compliance with hemodialysis treatments. DESIGN: A prospective observational study of patients undergoing hemodialysis in 1995 and a cross-sectional survey of health care professionals caring for hemodialyzed patients in 1996. SETTING AND PATIENTS: Four dialysis centers in the southeastern United States with 415 patients undergoing hemodialysis, 1 center in Sweden with 84 patients, and 4 centers in Japan with 194 patients participated in the prospective observational study. In the cross-sectional survey, nurses and nephrologists from the United States (n = 49), Japan (n = 21), and Sweden (n = 16) responded to questions regarding the compliance of their patients undergoing hemodialysis. MAIN OUTCOME MEASURES: Percentage of patients who miss a dialysis treatment and number of missed dialysis treatments. RESULTS: Of 415 US patients, 147 missed 699 treatments over a 6-month period (28.1 missed treatments per 100 patient-months or 2.3% of all prescribed treatments). During a 3-month period, there were 0 missed treatments per 100 patient-months for patients from Japan and 0 missed treatments per 100 patient-months for patients from Sweden (P<.001). In the cross-sectional survey, the mean (SD) estimated percentage of patients missing a treatment per month was 4% (3%) for the United States, 0% for Japan, and 0.1% (3%) for Sweden (P<.001). CONCLUSIONS: Noncompliance is much more common in US patients undergoing hemodialysis than Swedish and Japanese patients. The implications of these results for international differences in survival deserve further study.

Dialysis modality and delayed graft function after cadaveric renal transplantation.

The purpose of this investigation was to compare outcomes in the immediate posttransplant period for hemodialysis (HD) and peritoneal (PD) dialysis patients who received cadaveric renal transplantation. Data were obtained from the United Network of Organ Sharing on all cadaveric graft recipients who were dialysis-dependent at the time of transplantation between April 1994 and December 1995. Baseline characteristics were compared between groups, and multivariate logistic regression was performed with outcome measures including urine production in the first 24 h posttransplantation (U24), requirement for dialysis in the first week posttransplant (FWDIAL), and treatment for acute rejection during the initial hospitalization. The odds of oliguria (not producing urine in the first 24 h) were 1.49 (1.28 to 1.74) times higher in HD versus PD patients. After adjustment for other comorbid conditions including age, gender, race, HLA mismatch, time on dialysis, panel-reactive antibodies, and cold and warm ischemia time, the odds of oliguria were 1.60 (1.14 to 2.25) times higher in black HD patients compared with PD patients and 1.29 (1.06 to 1.57) times higher in white HD patients. In a similar manner, after adjustment for significant comorbid conditions, the odds of requiring dialysis in the first week were 1.56 (1.22 to 2.0) times higher in black HD patients versus PD patients and 1.40 (1.21 to 1.60) times higher in white HD patients. The rate of acute rejection was similar during the first hospitalization. These results suggest that there is an association between hemodialysis and delayed graft function. Differences in biocompatibility between the two modalities could potentially be responsible.

Replacement of amino acid and protein losses with 1.1% amino acid peritoneal dialysis solution.

OBJECTIVE: Losses of nutrients into dialysate may contribute to malnutrition. Peritoneal dialysis (PD) patients are reported to lose 3-4 g/day of amino acids (AAs) and 4-15 g/day of proteins. The extent to which one exchange with a 1.1% AA dialysis solution (Nutrineal, Baxter, Deerfield, IL, U.S.A.) offsets these losses was investigated in a 3-day inpatient study in 20 PD patients. DESIGN: Simple, open-label, cross-over study on consecutive days in a clinical research unit. On day 1 all patients were given a peritoneal equilibration test (PET). On day 2 they received 1.5% dextrose Dianeal (Baxter) as the first exchange of the day and their usual regimen thereafter. On day 3, the first exchange of the day was the 1.1% AA solution in place of 1.5% Dianeal and the usual PD regimen thereafter. On days 2 and 3 all dialysate effluent was collected and analyzed for AAs and proteins. Patients were maintained on a constant diet. RESULTS: Losses of AAs and total proteins on day 2 were 3.4 +/- 0.9 g and 5.8 +/- 2.4 g, respectively, totaling 9.2 +/- 2.7 g. The net uptake of AAs on day 3 was 17.6 +/- 2.6 g (80 +/- 12% of the 22 g infused). Mean gains of AAs on day 3 exceeded losses of proteins and AAs on day 2, p < 0.001. Losses of total proteins, but not losses of AAs, and the net absorption of AAs from the dialysis solution were correlated directly with peritoneal membrane transport characteristics, obtained from the PET. CONCLUSION: Daily losses of AAs and proteins into dialysate are more than offset by gains of AAs absorbed from one exchange with 1.1% AA-based dialysis solution. Net gains of AAs exceeded losses of proteins and AAs in all patients studied. The difference was relatively constant across a wide range of membrane transport types. Net AA gains were approximately two times the total AA and protein losses.

The Kidney Outcomes Prediction and Evaluation (KOPE) study: a prospective cohort investigation of patients undergoing hemodialysis. Study design and baseline characteristics.

PURPOSE: The purpose of the Kidney Outcomes Prediction and Evaluation (KOPE) study, was to more fully characterize the end-stage renal disease (ESRD) population with respect to social, psychological, and clinical characteristics, and to prospectively study the biomedical, social, and psychological factors that influence a range of ESRD outcomes in a large observational study of black and white patients on hemodialysis. This paper focuses on the KOPE study design as well as characteristics of patients at baseline. METHODS: KOPE was a prospective cohort investigation of patients treated at four dialysis centers in Forsyth County, North Carolina. Participants were interviewed at the dialysis centers, semi-annually over a 3 1/2 year period. Prevalent cases who were being treated with hemodialysis at the initiation of the study were enrolled into KOPE. Incident cases were subsequently enrolled as they presented to the participating units for hemodialysis. A total of 304 prevalent and 162 incident cases were enrolled into the study. The baseline health and sociodemographic characteristics of KOPE participants reported in this paper were obtained from medical records and Southeast Kidney Council data. Laboratory values taken within a 30-day interval around the baseline interview are also reported. RESULTS: KOPE participants differ from national statistics on race, age, and gender. Differences between KOPE participants and patients living in the region, but who did not participate in the study, can be explained by our recruitment criteria. CONCLUSIONS: KOPE will enable the characterization of the ESRD population, identification of factors related to poor outcomes, and identification of opportunities for interventions to prevent death and morbidity.