Grouping synergy generates the kin-selected benefit of bee workers

Endogenous P300 and exogenous slow vertex potentials were obtained with tone and speech stimuli in a group of five children using a cochlear implant (CI) with poor speech recognition (group A) and compared with those from another group of five children using a CI with good speech recognition (group B). The responses were also compared to those of children with normal hearing (n= 14) and a group of adult CI users (n=9). N1 and P2 latencies of CI group A and group B were prolonged compared to those of normally-hearing children. In group A, P300 was present when contrasts with tone stimuli were used. When speech stimuli were used, P300 potentials were absent or delayed. P300 potentials obtained in group B were no different from those obtained in normally-hearing children. It is suggested that the poor results evoked with speech stimuli in contrast to those evoked with pure-tone stimuli in group A are due to the immaturity of (sub) cortical generators associated with acoustical and phonetic processing. In contrast to the children in group B, all children in group A suffered from congenital deafness

Nature of collective decision-making by simple yes/no decision units Eisuke Hasegawa

The study of collective decision-making spans various fields such as brain and behavioural sciences, economics, management sciences, and artificial intelligence. Despite these interdisciplinary applications, little is known regarding how a group of simple 'yes/no' units, such as neurons in the brain, can select the best option among multiple options. One prerequisite for achieving such correct choices by the brain is correct evaluation of relative option quality, which enables a collective decision maker to efficiently choose the best option. Here, we applied a sensory discrimination mechanism using yes/no units with differential thresholds to a model for making a collective choice among multiple options. The performance corresponding to the correct choice was shown to be affected by various parameters. High performance can be achieved by tuning the threshold distribution with the options' quality distribution. The number of yes/no units allocated to each option and its variability profoundly affects performance. When this variability is large, a quorum decision becomes superior to a majority decision under some conditions. The general features of this collective decision-making by a group of simple yes/no units revealed in this study suggest that this mechanism may be useful in applications across various fields

A Unique Conjunction: Evidence for Gynogenesis Accompanying Haplodiploid Sex Determination in the Australian Ant Myrmecia impaternata Taylor

Myrmecia impaternata is an allodiploid all-female species of hybrid origin. Its parental taxa are confirmed here to be M. banksi and M. pilosula. We suggest that its queens produce diploid female offspring by gynogenetic parthenogenesis, a process which requires interaction between unreduced maternal oocytes and allospecific sperm cells obtained by copulation with another related species. We propose that impaternata queens almost certainly mate for this purpose with males reared in impaternata nests from eggs laid by impaternata females. Because sex in ants is determined by haplodiploidy (males haploid, females diploid), we posit that these males would in fact not be technically conspecific with the females in whose reproductive systems they developed, since they would each carry the haploid genome of one or other of the hybridic parental species. They would therefore be individually identical karyologically to males of either M. banksi or M. pilosula and appropriately allospecific to M. impaternata. We postulate that, unlike all other known gynogens, M. impaternata would have no need to maintain parasitic affiliation or sympatry with free-living sperm-donor host species. Its queens are arguably able to produce the required allospecific males by accessing their own genomes. M. impaternata apparently originated by instantaneous speciation when individuals of its parental species first successfully hybridized

Proposal of Classification Criteria for HTLV-1-Associated Myelopathy/Tropical Spastic Paraparesis Disease Activity

Human T-lymphotropic virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a rare chronic neuroinflammatory disease. While the disease usually progresses slowly without remission, there is a subgroup of patients with rapid progression and another subgroup with very slow progression. However, there have been no reports to date that have successfully determined the criteria to differentiate these subgroups. Therefore, we initially conducted a statistical modeling analysis to explore representative patterns of disease progression using data from our nationwide HAM/TSP patient registration system (“HAM-net”). The latent class mixed model analysis on the retrospective data (n = 205) of disease progression measured by the change in Osame Motor Disability Score from the onset of the disease to diagnosis demonstrated three representative progression patterns of HAM/TSP. Next, to test the effect of the progression rate at the initial phase of the disease on long-term prognosis, we divided 312 “HAM-net” registered patients into three groups (rapid, slow, and very slow progressors) based on the progression rate, then analyzed long-term functional prognosis of each group using the Kaplan–Meier method. Our data clearly demonstrated that the rapid progression at the early phase of the disease is an important poor prognostic factor. Moreover, to determine the biomarkers capable of discriminating the difference in disease activity, we compared the value of potential biomarkers of HAM/TSP among rapid (n = 15), slow (n = 74), very slow (n = 7), and controls (non-HAM/TSP patients, n = 18). The cerebrospinal fluid (CSF) levels of neopterin and C-X-C motif chemokine 10 (CXCL10) were the most valuable markers to discriminate among rapid, slow, and very slow progressors. To differentiate between rapid and slow progressors, the cut-off values of neopterin and CXCL10 were determined to be 44 pmol/mL and 4400 pg/mL, respectively. Furthermore, to differentiate between slow and very slow progressors, these values were determined to be 5.5 pmol/mL and 320 pg/mL, respectively. Notably, we found that CSF levels of these markers in very slow progressors were within the reference range. Thus, we propose a new classification criteria for disease activity of HAM/TSP that may contribute to improving the treatment algorithm for HAM/TSP

What Is True Halving in the Payoff Matrix of Game Theory?

In game theory, there are two social interpretations of rewards (payoffs) for decision-making strategies: (1) the interpretation based on the utility criterion derived from expected utility theory and (2) the interpretation based on the quantitative criterion (amount of gain) derived from validity in the empirical context. A dynamic decision theory has recently been developed in which dynamic utility is a conditional (state) variable that is a function of the current wealth of a decision maker. We applied dynamic utility to the equal division in dove-dove contests in the hawk-dove game. Our results indicate that under the utility criterion, the half-share of utility becomes proportional to a player’s current wealth. Our results are consistent with studies of the sense of fairness in animals, which indicate that the quantitative criterion has greater validity than the utility criterion. We also find that traditional analyses of repeated games must be reevaluated

The Optimal Caste Ratio in Polymorphic Ants : Estimation and Empirical Evidence

A simple model is proposed for estimation of the optimal caste composition in polymorphic ants. The model gives the optimal caste composition as the highest point on a hypersurface that represents the total efficiency of the colony as a whole. The hypersurface is the product of all partial efficiency surfaces for all tasks. The model was applied to the dimorphic ant Colobopsis nipponicus to test its utility. The ergonomic efficiency of the colony as a whole was estimated from the quantitative ability of each caste to perform each role. When all partial functions of the major workers were included in the model, the predicted optimal ratio closely reflects the observed caste ratio in the field. In addition, the pattern of changes in brood productivity upon experimental manipulation of the caste ratio was consistent with the pattern predicted from the model. These results suggest that the model is useful for estimations of the optimal caste ratio and that the caste ratio in field colonies is tuned to maximize the ergonomic efficiency of the colony as a whole through colony-level selection