An experiment on Prisoner’s Dilemma with confirmed proposals

We suggest an alternating proposals protocol with a confirmation stage as a way of solving a Prisoner’s Dilemma game. We interpret players’ proposals and (no) confirmation of outcomes of the game as a tacit communication device. The protocol leads to unprecedented high levels of cooperation in the laboratory. Assigning the power of confirmation to one of the two players alone, rather than alternating the role of a leader significantly increases the probability of cooperation in the first bargaining period. We interpret pre-agreement strategies as tacit messages on players’ willingness to cooperate and as signals pursuing individualistic objectives like publicizing one’s bargaining abilities or eliciting those of the opponent.     

Phonological alexia with vowel-consonant dissociation in non-word reading

We present a patient with alexia secondary to cerebral lesion whose errors in the reading of non-words affect vowels more than consonants. The interest of the case resides in: (1) the documentation of a vowel-consonant dissociation selectively affecting the reading of non-words; and (2) the localization of the alteration in a specific stage of the perilexical reading pathway, that is, the blending of phonetic chains. The case contributes to the discussion on the nature of representations and the processing of vowels and consonants.     

Decision problems for classes of diagonalizable algebras

We make use of a Theorem of Burris-McKenzie to prove that the only decidable variety of diagonalizable algebras is that defined by 0=1. Any variety containing an algebra in which 01 is hereditarily undecidable. Moreover, any variety of intuitionistic diagonalizable algebras is undecidable.     

Effects of stress on defensive aggression and dominance in a water competition test

Water-deprived rats in a pair competing for a single source of water quickly establish a firm relationship during which one rat drinks consistently more (dominant) than the other (submissive) animal. This relationship is formed during the first competition and is very stable during subsequent tests. Exposure of dominant rats to a severe (18 hrs immobilization), but not a mild (2 hrs immobilization), stressor reduced markedly aggressive behavior and inverted transiently the dominant submissive relationship of the pairs. Exposure of submissive rats to the severe stressor resulted in only minor reductions of aggressive behavior in these animals. Prestress anxiety predicted stress effects in the dominant animals in that high-anxious animals lost more dominant behavior and weight during stress as compared with low-anxious rats. Thus, severe stress can transiently reduce dominant but not submissive behavior during water competition and high-anxious rats are more prone to lose their aggressive behavior.     

A Preliminary Study of MV-Algebras with Two Quantifiers Which Commute

In this paper we investigate the class of MV-algebras equipped with two quantifiers which commute as a natural generalization of diagonal-free two-dimensional cylindric algebras (see Henkin et al., in Cylindric algebras, 1985). In the 40s, Tarski first introduced cylindric algebras in order to provide an algebraic apparatus for the study of classical predicate calculus. The diagonal–free two-dimensional cylindric algebras are special cylindric algebras. The treatment here of MV-algebras is done in terms of implication and negation. This allows us to simplify some results due to Di Nola and Grigolia (Ann Pure Appl Logic 128(1-3):125–139, 2004) related to the characterization of a quantifier in terms of some special sub-algebra associated to it. On the other hand, we present a topological duality for this class of algebras and we apply it to characterize the congruences of one algebra via certain closed sets. Finally, we study the subvariety of this class generated by a chain of length n + 1 (n <  ω). We prove that the subvariety is semisimple and we characterize their simple algebras. Using a special functional algebra, we determine all the simple finite algebras of this subvariety.     

Neophobia is negatively related to reversal learning ability in females of a generalist bird of prey,the Chimango Caracara, <Emphasis Type="Italic">Milvago chimango</Emphasis>

In an ever-changing environment, the ability to adapt choices to new conditions is essential for daily living and ultimately, for survival. Behavioural flexibility allows animals to maximise survival and reproduction in novel settings by adjusting their behaviour based on specific information and feedback acquired in their current environments. However, a growing body of evidence indicates that an individual’s personality type can limit the extent to which the individual might behave flexibly, by influencing the way an individual pays attention to novelty and how much information it collects and stores, which in turn affects the individual’s decision-making and learning process. In this study, the behavioural flexibility of a generalist predator, the Chimango Caracara, Milvago chimango, was analysed using the reversal learning paradigm, focusing on the comparison between age classes, and the relation of learning flexibility with a personality trait, the level of neophobia. Due to the low number of male individuals captured, this study was carried out only with female birds. The results showed that age had no significant effect either on the acquisition of a stimulus-reward association, or on the capacity of reversing this previously learned association. Reversal of the response was a harder task for these birds in comparison with the initial acquisition process. The individual’s performances in the learning tasks seemed to be uncorrelated with each other, suggesting that they involve different neural mechanisms. Contrary to the general pattern observed in the majority of previous work on personality and cognition in non-human animals, the level of neophobia did not correlate with the initial associative learning performance in both adults and juveniles, yet it showed a significant negative relationship with reversal learning ability, mainly in the regressive phase of this task, for the two age classes. Our results suggest that the predatory and generalist lifestyle of female individuals of M. chimango along with the selective pressures of the environment of the individuals studied might play a critical role in the degree and direction of the linkage between novelty response and learning flexibility observed in this study.     

Limitations in Verbal Fluency Following Heavy Burdens of Early Childhood Diarrhea in Brazilian Shantytown Children

The effects of heavy burdens of diarrhea in the first 2 years of life on specific executive control function like verbal fluency are not well understood. In previous studies, we have shown associations of early childhood diarrhea (ECD) with nonverbal intelligence and school functioning. Therefore, we postulated that ECD might affect early neuropsychological development leading to long-term deficits in normal cognitive development. Based on our extensive 14-year prospective cohort studies of early childhood diarrheal illnesses in a Brazilian shantytown community, we examined ECD correlations between specific impairments of higher mental function and executive skills in shantytown children 5–10 years later (now at 6–12) years of age. Specifically we examined whether heavy diarrheal illnesses correlate with reduced performance on selected tests of executive function. Our study, for the first time, suggests a disproportional impairment in semantic but not phonetic fluency in a subset of children with heavy burdens of diarrhea in their first 2 years of life even when controlling for maternal education, breastfeeding, and child schooling. Similar semantic decrements have been associated with impaired recovery from brain injury. These exploratory studies suggest the importance of verbal fluency tests to assess executive functioning in children challenged by poor nutrition and diarrhea in early life. In addition, our unique findings show the potential influences of early childhood diarrhea on language development that is so critical to productive adulthood and potentially set a foundation for new neuropsychological approaches, which assess early burdens of enteric illnesses on childhood development.     

Predicting perceived image quality: a critique of Lin and Kuo (2011)

A recent study by Lin and Kuo reported on the image quality of a small mobile display under different ambient illumination levels. In this commentary, the present author discusses the limitations of their approach with respect to the rigorous quantification of image quality and the caveats associated with preference studies of new display technologies. Quantitatively predicting image quality using preference-based methods can be useful for initial decisions in early phases of product development, but provides limited value for the rigorous quantification of image quality of display devices.     

Gaze orientation interferes with mental numerical representation

Number comparison tasks are characterized by distance and size effects. The distance effect reveals that the higher the distance is between two numbers, the easier their magnitude comparison is. Accordingly, people are thought to represent numbers on a spatial dimension, the mental number line, on which any given number corresponds to a location on the line. The size effect, instead, states that at any given distance, comparing two small numbers is easier than comparing two large numbers, thus suggesting that larger numbers are more vaguely represented than smaller ones. In the present work we first tested whether the participants were adopting a spatial strategy to solve a very simple numbers comparison task, by assessing the presence of the distance and the magnitude effect. Secondarily, we focused on the influence of gaze position on their performance. The present results provide evidence that gaze direction interferes with number comparisons, worsening the vague representation of larger numbers and further supporting the hypothesis of the overlapping between physical and mental spaces.     

What's in a function?

In this paper we argue that Revision Rules, introduced by Anil Gupta and Nuel Belnap as a tool for the analysis of the concept of truth, also provide a useful tool for defining computable functions. This also makes good on Gupta's and Belnap's claim that Revision Rules provide a general theory of definition, a claim for which they supply only the example of truth. In particular we show how Revision Rules arise naturally from relaxing and generalizing a classical construction due to Kleene, and indicate how they can be employed to reconstruct the class of the general recursive functions. We also point at how Revision Rules can be employed to access non-minimal fixed points of partially defined computing procedures.I thank Nuel Belnap, Rich Thomason, Ken Manders, and Jamie Tappenden for much helpful advice given while I was trying to get clear on the ideas presented here. I also thank two anonymous referees for helpful comments and criticisms on an earlier version of this paper.