Decision Rules and Group Rationality: Cognitive Gain or Standstill?

Recent research in group cognition points towards the existence of collective cognitive competencies that transcend individual group members’ cognitive competencies. Since rationality is a key cognitive competence for group decision making, and group cognition emerges from the coordination of individual cognition during social interactions, this study tests the extent to which collaborative and consultative decision rules impact the emergence of group rationality. Using a set of decision tasks adapted from the heuristics and biases literature, we evaluate rationality as the extent to which individual choices are aligned with a normative ideal. We further operationalize group rationality as cognitive synergy (the extent to which collective rationality exceeds average or best individual rationality in the group), and we test the effect of collaborative and consultative decision rules in a sample of 176 groups. Our results show that the collaborative decision rule has superior synergic effects as compared to the consultative decision rule. The ninety one groups working in a collaborative fashion made more rational choices (above and beyond the average rationality of their members) than the eighty five groups working in a consultative fashion. Moreover, the groups using a collaborative decision rule were closer to the rationality of their best member than groups using consultative decision rules. Nevertheless, on average groups did not outperformed their best member. Therefore, our results reveal how decision rules prescribing interpersonal interactions impact on the emergence of collective cognitive competencies. They also open potential venues for further research on the emergence of collective rationality in human decision-making groups.     

The Gambler’s Fallacy Is Associated with Weak Affective Decision Making but Strong Cognitive Ability

Humans demonstrate an inherent bias towards making maladaptive decisions, as shown by a phenomenon known as the gambler’s fallacy (GF). The GF has been traditionally considered as a heuristic bias supported by the fast and automatic intuition system, which can be overcome by the reasoning system. The present study examined an intriguing hypothesis, based on emerging evidence from neuroscience research, that the GF might be attributed to a weak affective but strong cognitive decision making mechanism. With data from a large sample of college students, we found that individuals’ use of the GF strategy was positively correlated with their general intelligence and executive function, such as working memory and conflict resolution, but negatively correlated with their affective decision making capacities, as measured by the Iowa Gambling Task. Our result provides a novel insight into the mechanisms underlying the GF, which highlights the significant role of affective mechanisms in adaptive decision-making.     

Differences in Nutrient Requirements Imply a Non-Linear Emergence of Leaders in Animal Groups

Collective decision making and especially leadership in groups are among the most studied topics in natural, social, and political sciences. Previous studies have shown that some individuals are more likely to be leaders because of their social power or the pertinent information they possess. One challenge for all group members, however, is to satisfy their needs. In many situations, we do not yet know how individuals within groups distribute leadership decisions between themselves in order to satisfy time-varying individual requirements. To gain insight into this problem, we build a dynamic model where group members have to satisfy different needs but are not aware of each other''s needs. Data about needs of animals come from real data observed in macaques. Several studies showed that a collective movement may be initiated by a single individual. This individual may be the dominant one, the oldest one, but also the one having the highest physiological needs. In our model, the individual with the lowest reserve initiates movements and decides for all its conspecifics. This simple rule leads to a viable decision-making system where all individuals may lead the group at one moment and thus suit their requirements. However, a single individual becomes the leader in 38% to 95% of cases and the leadership is unequally (according to an exponential law) distributed according to the heterogeneity of needs in the group. The results showed that this non-linearity emerges when one group member reaches physiological requirements, mainly the nutrient ones – protein, energy and water depending on weight - superior to those of its conspecifics. This amplification may explain why some leaders could appear in animal groups without any despotism, complex signalling, or developed cognitive ability.     

Cognitive Distance,Absorptive Capacity and Group Rationality: A Simulation Study

We report the results of a simulation study in which we explore the joint effect of group absorptive capacity (as the average individual rationality of the group members) and cognitive distance (as the distance between the most rational group member and the rest of the group) on the emergence of collective rationality in groups. We start from empirical results reported in the literature on group rationality as collective group level competence and use data on real-life groups of four and five to validate a mathematical model. We then use this mathematical model to predict group level scores from a variety of possible group configurations (varying both in cognitive distance and average individual rationality). Our results show that both group competence and cognitive distance are necessary conditions for emergent group rationality. Group configurations, in which the groups become more rational than the most rational group member, are groups scoring low on cognitive distance and scoring high on absorptive capacity.     

Does the community want devolved authority? Results of deliberative polling in Ontario.

OBJECTIVE: To obtain and contrast the informed opinions of people in five decision-making groups that could have a role in devolved governance of health care and social services. DESIGN: Deliberative polling. SETTING: Three rural and three urban communities selected from the 32 areas covered by a district health council in Ontario. PARTICIPANTS: A total of 280 citizens from five potential decision-making groups: randomly selected citizens, attendees at town-hall meetings, appointees to district health councils, elected officials and experts in health care and social services. INTERVENTION: Participants'' opinions were polled during 29 structured 2-hour meetings. MAIN OUTCOME MEASURES: Participants'' opinions on their personal willingness and their group''s suitability to be involved in devolved decision making, desired type of decision-making involvement, information preferences, preferred areas of decision-making involvement and preferred composition of decision-making bodies. RESULTS: Mean attendance at each meeting was 9.6 citizens. Although there were some significant differences in opinion among the five potential decision-making groups, there were few differences among citizens from different geographic areas. A total of 189 (72%) of people polled were personally willing to take on a role involving responsibility for overall decision-making, but far fewer thought that their group was suited to taking on responsibility (30%) or a consulting role (55%). Elected officials were the most willing (85% personally willing, 50% thought their group was suitable) and randomly selected citizens the least willing (60% personally willing, 17% thought their group was suitable) to take responsibility for overall decision making. Most citizens polled indicated less interest in involvement in specific types of decisions, except for planning and setting priorities, than in overall decision making. Only 24 participants (9%) rated their own group as suitable to take responsibility for raising revenue, 91 (33%) deemed their group suited to distribution of funds and 108 (39%) felt their group was suitable for management of services. People in all five groups ranked health care needs (mean rank 1.5 out of four options) as the most important and preferences (mean rank 3.6) as the least important information. They rated a combination body involving several community groups as the most suitable overall decision-making body (8.8 on 10-point scale). Participants favoured the representation of elected officials, the provincial government and experts on combination bodies responsible for the specific types of decisions. Overall, as the complexity of devolved decision making became clear, participants tended to assign authority to traditional decision makers such as elected officials, experts and the provincial government, but also favoured a consulting role for attendees at town-hall meetings (i.e., interested citizens). CONCLUSION: There are significant differences among groups in the community in their willingness to be involved, desired roles and representation in devolved decision making on health care and social services in Ontario.     

A simple threshold rule is sufficient to explain sophisticated collective decision-making

Decision-making animals can use slow-but-accurate strategies, such as making multiple comparisons, or opt for simpler, faster strategies to find a 'good enough' option. Social animals make collective decisions about many group behaviours including foraging and migration. The key to the collective choice lies with individual behaviour. We present a case study of a collective decision-making process (house-hunting ants, Temnothorax albipennis), in which a previously proposed decision strategy involved both quality-dependent hesitancy and direct comparisons of nests by scouts. An alternative possible decision strategy is that scouting ants use a very simple quality-dependent threshold rule to decide whether to recruit nest-mates to a new site or search for alternatives. We use analytical and simulation modelling to demonstrate that this simple rule is sufficient to explain empirical patterns from three studies of collective decision-making in ants, and can account parsimoniously for apparent comparison by individuals and apparent hesitancy (recruitment latency) effects, when available nests differ strongly in quality. This highlights the need to carefully design experiments to detect individual comparison. We present empirical data strongly suggesting that best-of-n comparison is not used by individual ants, although individual sequential comparisons are not ruled out. However, by using a simple threshold rule, decision-making groups are able to effectively compare options, without relying on any form of direct comparison of alternatives by individuals. This parsimonious mechanism could promote collective rationality in group decision-making.     

The Merits of Unconscious Thought in Rule Detection

According to unconscious thought theory (UTT), unconscious thought is more adept at complex decision-making than is conscious thought. Related research has mainly focused on the complexity of decision-making tasks as determined by the amount of information provided. However, the complexity of the rules generating this information also influences decision making. Therefore, we examined whether unconscious thought facilitates the detection of rules during a complex decision-making task. Participants were presented with two types of letter strings. One type matched a grammatical rule, while the other did not. Participants were then divided into three groups according to whether they made decisions using conscious thought, unconscious thought, or immediate decision. The results demonstrated that the unconscious thought group was more accurate in identifying letter strings that conformed to the grammatical rule than were the conscious thought and immediate decision groups. Moreover, performance of the conscious thought and immediate decision groups was similar. We conclude that unconscious thought facilitates the detection of complex rules, which is consistent with UTT.     

Conservatism and Adaptability during Squirrel Radiation: What Is Mandible Shape Telling Us?

Both functional adaptation and phylogeny shape the morphology of taxa within clades. Herein we explore these two factors in an integrated way by analyzing shape and size variation in the mandible of extant squirrels using landmark-based geometric morphometrics in combination with a comparative phylogenetic analysis. Dietary specialization and locomotion were found to be reliable predictors of mandible shape, with the prediction by locomotion probably reflecting the underlying diet. In addition a weak but significant allometric effect could be demonstrated. Our results found a strong phylogenetic signal in the family as a whole as well as in the main clades, which is in agreement with the general notion of squirrels being a conservative group. This fact does not preclude functional explanations for mandible shape, but rather indicates that ancient adaptations kept a prominent role, with most genera having diverged little from their ancestral clade morphologies. Nevertheless, certain groups have evolved conspicuous adaptations that allow them to specialize on unique dietary resources. Such adaptations mostly occurred in the Callosciurinae and probably reflect their radiation into the numerous ecological niches of the tropical and subtropical forests of Southeastern Asia. Our dietary reconstruction for the oldest known fossil squirrels (Eocene, 36 million years ago) show a specialization on nuts and seeds, implying that the development from protrogomorphous to sciuromorphous skulls was not necessarily related to a change in diet.     

Synaptic plasticity and connectivity requirements to produce stimulus-pair specific responses in recurrent networks of spiking neurons

Animals must respond selectively to specific combinations of salient environmental stimuli in order to survive in complex environments. A task with these features, biconditional discrimination, requires responses to select pairs of stimuli that are opposite to responses to those stimuli in another combination. We investigate the characteristics of synaptic plasticity and network connectivity needed to produce stimulus-pair neural responses within randomly connected model networks of spiking neurons trained in biconditional discrimination. Using reward-based plasticity for synapses from the random associative network onto a winner-takes-all decision-making network representing perceptual decision-making, we find that reliably correct decision making requires upstream neurons with strong stimulus-pair selectivity. By chance, selective neurons were present in initial networks; appropriate plasticity mechanisms improved task performance by enhancing the initial diversity of responses. We find long-term potentiation of inhibition to be the most beneficial plasticity rule by suppressing weak responses to produce reliably correct decisions across an extensive range of networks.     

Shared or unshared consensus decision in macaques?

Members of a social group have to make collective decisions in order to synchronise their activities. In a shared consensus decision, all group members can take part in the decision whereas in an unshared consensus decision, one individual, usually a dominant member of the group, takes the decision for the rest of the group. It has been suggested that the type of decision-making of a species could be influenced by its social style. To investigate this further, we studied collective movements in two species with opposed social systems, the Tonkean macaque (Macaca tonkeana) and the rhesus macaque (Macaca mulatta). From our results, it appears that the decision to move is the result of the choices and actions of several individuals in both groups. However, this consensus decision involved nearly all group members in Tonkean macaques whereas dominant and old individuals took a prominent role in rhesus macaques. Thus, we suggest that Tonkean macaques display equally shared consensus decisions to move, whereas in the same context rhesus macaque exhibit partially shared consensus decisions. Such a difference in making a collective decision might be linked to the different social systems of the two studied species.     

Using BRAFV600E as a marker of autophagy dependence in pediatric brain tumors

Autophagy inhibition is a potential therapeutic strategy in central nervous system (CNS) tumors. The BRAF^V600E mutation is known to affect autophagy. Our studies indicate CNS tumor cells with BRAF^V600E mutant cells (but not wild type) display high rates of induced autophagy, are sensitive to autophagy inhibition, and display synergy when chloroquine is combined with the RAF kinase inhibitor vemurafenib or standard chemotherapeutics. Our studies also indicate chloroquine can improve vemurafenib sensitivity in intrinsically resistant cells and in a patient with induced-vemurafenib resistance. These findings suggest CNS tumors with BRAF^V600E are autophagy-dependent and that identification of BRAF^V600E may be a marker to identify pediatric patients with the best potential response to autophagy inhibition.     

Using BRAFV600E as a marker of autophagy dependence in pediatric brain tumors

Autophagy inhibition is a potential therapeutic strategy in central nervous system (CNS) tumors. The BRAF^V600E mutation is known to affect autophagy. Our studies indicate CNS tumor cells with BRAF^V600E mutant cells (but not wild type) display high rates of induced autophagy, are sensitive to autophagy inhibition, and display synergy when chloroquine is combined with the RAF kinase inhibitor vemurafenib or standard chemotherapeutics. Our studies also indicate chloroquine can improve vemurafenib sensitivity in intrinsically resistant cells and in a patient with induced-vemurafenib resistance. These findings suggest CNS tumors with BRAF^V600E are autophagy-dependent and that identification of BRAF^V600E may be a marker to identify pediatric patients with the best potential response to autophagy inhibition.     

When Does Diversity Trump Ability (and Vice Versa) in Group Decision Making? A Simulation Study

It is often unclear which factor plays a more critical role in determining a group's performance: the diversity among members of the group or their individual abilities. In this study, we addressed this "diversity vs. ability" issue in a decision-making task. We conducted three simulation studies in which we manipulated agents' individual ability (or accuracy, in the context of our investigation) and group diversity by varying (1) the heuristics agents used to search task-relevant information (i.e., cues); (2) the size of their groups; (3) how much they had learned about a good cue search order; and (4) the magnitude of errors in the information they searched. In each study, we found that a manipulation reducing agents' individual accuracy simultaneously increased their group's diversity, leading to a conflict between the two. These conflicts enabled us to identify certain conditions under which diversity trumps individual accuracy, and vice versa. Specifically, we found that individual accuracy is more important in task environments in which cues differ greatly in the quality of their information, and diversity matters more when such differences are relatively small. Changing the size of a group and the amount of learning by an agent had a limited impact on this general effect of task environment. Furthermore, we found that a group achieves its highest accuracy when there is an intermediate amount of errors in the cue information, regardless of the environment and the heuristic used, an effect that we believe has not been previously reported and warrants further investigation.     

The Role of a Hospital Ethics Consultation Service in Decision-Making for Unrepresented Patients

Despite increased calls for hospital ethics committees to serve as default decision-makers about life-sustaining treatment (LST) for unrepresented patients who lack decision-making capacity or a surrogate decision-maker and whose wishes regarding medical care are not known, little is known about how committees currently function in these cases. This was a retrospective cohort study of all ethics committee consultations involving decision-making about LST for unrepresented patients at a large academic hospital from 2007 to 2013. There were 310 ethics committee consultations, twenty-five (8.1 per cent) of which involved unrepresented patients. In thirteen (52.0 per cent) cases, the ethics consultants evaluated a possible substitute decision-maker identified by social workers and/or case managers. In the remaining cases, the ethics consultants worked with the medical team to contact previous healthcare professionals to provide substituted judgement, found prior advance care planning documents, or identified the patient’s best interest as the decision-making standard. In the majority of cases, the final decision was to limit or withdraw LST (72 per cent) or to change code status to Do Not Resuscitate/Do Not Intubate (12 per cent). Substitute decision-makers who had been evaluated through the ethics consultation process and who made the final decision alone were more likely to continue LST than cases in which physicians made the final decision (50 per cent vs 6.3 per cent, p = 0.04). In our centre, the primary role of ethics consultants in decision-making for unrepresented patients is to identify appropriate decision-making standards. In the absence of other data suggesting that ethics committees, as currently constituted, are ready to serve as substitute decision-makers for unrepresented patients, caution is necessary before designating these committees as default decision-makers.     

Nerve and behavioral responses of mice to various umami substances

Food contains various taste substances. Among them, umami substances play an important role with regard to the perception of the taste of food, but, few studies have examined the taste characteristics of representative umami substances other than monosodium L-glutamate (MSG). By conducting mouse behavioral studies (the 48-h 2-bottle preference test and the conditioned taste aversion test) and assessing gustatory nerve responses, we investigated the taste characteristics of unique umami substances, including sodium succinate, L-theanine, betaine, and the enantiomer of MSG, D-MSG. Furthermore, we examined the synergy of umami with inosine 5'-monophoshate (IMP). In the case of the mice, sodium succinate had an umami taste and showed strong synergy with IMP. L-theanine showed synergy with IMP but did not have an umami taste without IMP. In contrast, betaine did not have an umami taste or synergy with IMP. D-MSG might have weak synergy with IMP.     

Corvids avoid odd evaluation by following simple rules in a risky exchange task

In their natural environment, animals often make decisions crucial for survival, such as choosing the best patch or food, or the best partner to cooperate. The choice can be compared to a gamble with an outcome that is predictable but not certain, such as rolling a dice. In economics, such a situation is called a risky context. Several models show that although individuals can generally evaluate the odds of each potential outcome, they can be subject to errors of judgment or choose according to decision-making heuristics (simple decision rules). In non-human primates, similar errors of judgment have been reported and we have recently shown that they also use a decisional heuristics when confronted with a risky choice in an exchange task. This suggests a common evolutionary origin to the mechanisms underlying decision-making under risk in primates. However, whether the same mechanisms are also present in more distantly related taxa needs to be further investigated. Other social species, like corvids, are renowned for their advanced cognitive skills and may show similar responses. Here, we analyse data on corvids (carrion crows, hooded crows, common ravens and rooks) tested in a risky exchange task comparable to the one used in non-human primates. We investigated whether corvids could exchange according to the odds of success or, alternatively, whether they used a heuristic similar to the one used by non-human primates. Instead, most corvids chose a course of action (either a low or high exchange rate) that remained constant throughout the study. In general, corvids’ mean exchange rates were lower compared to non-human primates, indicating that they were either risk-adverse or that they do not possess the cognitive capabilities to evaluate odds. Further studies are required to evaluate the flexibility in exchange abilities of these birds in exchange abilities of these birds.     

Group personality during collective decision-making: a multi-level approach

Collective decision-making processes emerge from social feedback networks within a group. Many studies on collective behaviour underestimate the role of individual personality and, as a result, personality is rarely analysed in the context of collective dynamics. Here, we show evidence of sheltering behaviour personality in a gregarious insect (Periplaneta americana), which is characterized by a collective personality at the group level. We also highlight that the individuals within groups exhibited consistent personality traits in their probability of sheltering and total time sheltered during the three trials over one week. Moreover, the group personality, which arises from the synergy between the distribution of behaviour profiles in the group and social amplifications, affected the sheltering dynamics. However, owing to its robustness, personality did not affect the group probability of reaching a consensus. Finally, to prove social interactions, we developed a new statistical method that will be helpful for future research on personality traits and group behaviour. This approach will help to identify the circumstances under which particular group compositions may improve the fitness of individuals in gregarious species.     

普氏原羚集群的群体决策过程

动物集群的群体行为决策是营集群生活的动物调节其群体活动、而获得集群生活收益的重要手段。受动物自身行为和需求的影响,动物集群的群体决策有不同的外在表现形式和过程。本研究以青海湖湖东地区的普氏原羚种群为对象,于2010 年3 月至2012 年3 月对普氏原羚集群的群体决策过程进行了观察和记录,并对所得数据采用非参数检验方法进行统计与分析,分析结果表明:1. 普氏原羚集群的群体决策类型为不完全民主型,需要有一定比例的个体共同参与群体决策过程才能达成群体决策,而参与群体决策的个体比例随群体规模的增加而降低;2.参与决策的个体因性别不同而有不同的表现,且在决策过程所需时间上存在差异,这可能是导致普氏原羚产生同性聚群现象的原因之一。这是在野外直接对大型有蹄类动物集群的群体决策过程进行的为数不多的研究,还需要更多的野外研究来探究不同类型动物群体决策过程及其与同性聚群产生机理之间的关系。     

BDNF polymorphism predicts general intelligence after penetrating traumatic brain injury

Neuronal plasticity is a fundamental factor in cognitive outcome following traumatic brain injury. Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, plays an important role in this process. While there are many ways to measure cognitive outcome, general cognitive intelligence is a strong predictor of everyday decision-making, occupational attainment, social mobility and job performance. Thus it is an excellent measure of cognitive outcome following traumatic brain injury (TBI). Although the importance of the single-nucleotide polymorphisms polymorphism on cognitive function has been previously addressed, its role in recovery of general intelligence following TBI is unknown. We genotyped male Caucasian Vietnam combat veterans with focal penetrating TBI (pTBI) (n = 109) and non-head injured controls (n = 38) for 7 BDNF single-nucleotide polymorphisms. Subjects were administrated the Armed Forces Qualification Test (AFQT) at three different time periods: pre-injury on induction into the military, Phase II (10–15 years post-injury, and Phase III (30–35 years post-injury). Two single-nucleotide polymorphisms, rs7124442 and rs1519480, were significantly associated with post-injury recovery of general cognitive intelligence with the most pronounced effect at the Phase II time point, indicating lesion-induced plasticity. The genotypes accounted for 5% of the variance of the AFQT scores, independently of other significant predictors such as pre-injury intelligence and percentage of brain volume loss. These data indicate that genetic variations in BDNF play a significant role in lesion-induced recovery following pTBI. Identifying the underlying mechanism of this brain-derived neurotrophic factor effect could provide insight into an important aspect of post-traumatic cognitive recovery.