Language evolution by iterated learning with bayesian agents

Languages are transmitted from person to person and generation to generation via a process of iterated learning: people learn a language from other people who once learned that language themselves. We analyze the consequences of iterated learning for learning algorithms based on the principles of Bayesian inference, assuming that learners compute a posterior distribution over languages by combining a prior (representing their inductive biases) with the evidence provided by linguistic data. We show that when learners sample languages from this posterior distribution, iterated learning converges to a distribution over languages that is determined entirely by the prior. Under these conditions, iterated learning is a form of Gibbs sampling, a widely-used Markov chain Monte Carlo algorithm. The consequences of iterated learning are more complicated when learners choose the language with maximum posterior probability, being affected by both the prior of the learners and the amount of information transmitted between generations. We show that in this case, iterated learning corresponds to another statistical inference algorithm, a variant of the expectation-maximization (EM) algorithm. These results clarify the role of iterated learning in explanations of linguistic universals and provide a formal connection between constraints on language acquisition and the languages that come to be spoken, suggesting that information transmitted via iterated learning will ultimately come to mirror the minds of the learners.     

Genes in the Postgenomic Era

We outline three very different concepts of the gene—instrumental, nominal, and postgenomic. The instrumental gene has a critical role in the construction and interpretation of experiments in which the relationship between genotype and phenotype is explored via hybridization between organisms or directly between nucleic acid molecules. It also plays an important theoretical role in the foundations of disciplines such as quantitative genetics and population genetics. The nominal gene is a critical practical tool, allowing stable communication between bioscientists in a wide range of fields grounded in well-defined sequences of nucleotides, but this concept does not embody major theoretical insights into genome structure or function. The post-genomic gene embodies the continuing project of understanding how genome structure supports genome function, but with a deflationary picture of the gene as a structural unit. This final concept of the gene poses a significant challenge to conventional assumptions about the relationship between genome structure and function, and between genotype and phenotype.     

The warpy thoughts scale: a new 20-item instrument to measure dysfunctional attitudes

Cognitive theories of psychopathology propose that specific negative cognitive schema held by individuals can increase their likelihood of experiencing depressive episodes. While it has been argued that such dysfunctional attitudes are state measures that occur primarily during periods of depression, a range of research has supported the view that holding dysfunctional attitudes is ongoing, persisting prior to and following depressive episodes. To date, the need for a parsimonious measure of dysfunctional attitudes has not been well addressed. Using data provided by 4545 participants in a free on-line cognitive behavioural therapy program, MoodGYM, we have developed the Warpy Thoughts Scale (WTS), a 20-item instrument measuring dysfunctional attitudes. This scale provides 3 first order factors (Relationships, Achievements and Entitlements) and a higher order factor, Warpy Thoughts, from which a Warpy Thoughts score can be obtained. Confirmatory factor analyses on this model indicated that it provides robust results for men and women and for individuals in a wide range of ages. WTS scores were moderately correlated with levels of depressive and anxiety symptoms (0.39 and 0.40, respectively) and explained up to one-fifth of the variance of these mental health measures. Further validation of the WTS against other measures of dysfunctional thoughts is required.     

Structure and strength in causal induction

We present a framework for the rational analysis of elemental causal induction-learning about the existence of a relationship between a single cause and effect-based upon causal graphical models. This framework makes precise the distinction between causal structure and causal strength: the difference between asking whether a causal relationship exists and asking how strong that causal relationship might be. We show that two leading rational models of elemental causal induction, DeltaP and causal power, both estimate causal strength, and we introduce a new rational model, causal support, that assesses causal structure. Causal support predicts several key phenomena of causal induction that cannot be accounted for by other rational models, which we explore through a series of experiments. These phenomena include the complex interaction between DeltaP and the base-rate probability of the effect in the absence of the cause, sample size effects, inferences from incomplete contingency tables, and causal learning from rates. Causal support also provides a better account of a number of existing datasets than either DeltaP or causal power.     

A multidimensional scaling approach to mental multiplication

Adults consistently make errors in solving simple multiplication problems. These errors have been explained with reference to the interference between similar problems. In this paper, we apply multidimensional scaling (MDS) to the domain of multiplication problems, to uncover their underlying similarity structure. A tree-sorting task was used to obtain perceived dissimilarity ratings. The derived representation shows greater similarity between problems containing larger operands and suggests that tie problems (e.g., 7 x 7) hold special status. A version of the generalized context model (Nosofsky, 1986) was used to explore the derived MDS solution. The similarity of multiplication problems made an important contribution to producing a model consistent with human performance, as did the frequency with which such problems arise in textbooks, suggesting that both factors may be involved in the explanation of errors.     

Virtual Deviance: Swinging and Swapping in an On-Line Network

The purpose of the current research is to study the virtual presentation of self in on-line profiles, specifically within a deviant subculture. The study explores the social construction of deviant identities using the on-line community of “swingers.” Our research explored what self-presentation strategies are employed by participants in their profiles to develop credibility to attract others to their profiles and what major concerns, expectations, and values characterize the profiles of the on-line swinger community. Most on-line profiles focus on developing credibility. We used Aristotle's notions of goodwill, practical intelligence, and virtue to categorize the specific means used in profiles to develop credibility.     

The Effects of Cultural Transmission Are Modulated by the Amount of Information Transmitted

Information changes as it is passed from person to person, with this process of cultural transmission allowing the minds of individuals to shape the information that they transmit. We present mathematical models of cultural transmission which predict that the amount of information passed from person to person should affect the rate at which that information changes. We tested this prediction using a function‐learning task, in which people learn a functional relationship between two variables by observing the values of those variables. We varied the total number of observations and the number of those observations that take unique values. We found an effect of the number of observations, with functions transmitted using fewer observations changing form more quickly. We did not find an effect of the number of unique observations, suggesting that noise in perception or memory may have affected learning.     

The “Making and Unmaking” of Prejudice Against Australian Muslims and Gay Men and Lesbians: The Role of Religious Development and Fundamentalism

Despite the growing international interest in the relation between religion and prejudice, there has been a dearth of studies conducted within Australia. We used the Faith Development Scale (FDS) to examine the relation between religious maturity and attitudes toward Muslims and toward gay men and lesbians in an Australian context using a sample of churchgoers from the Perth metropolitan area (N = 139). Respondents who scored lower on the FDS were more prejudiced toward both target groups than were high scorers. Furthermore, participants who scored lower on the FDS were more prejudiced against gay men and lesbians than they were against Muslim Australians. The FDS was a better predictor of attitudes toward the two groups than was the Quest Scale. Contrary to overseas studies, we found that religious fundamentalists held more prejudiced attitudes toward gay men and lesbians than toward those of a different religion (Australian Muslims). Right-wing political orientation was also found to be predictive of prejudice against Australian Muslims and against gay men and lesbians independently of religious development. Results suggest that religious maturity, as well as fundamentalism and right-wing political views, plays an important role in the “making” or “unmaking” of prejudice against Australian Muslims and against gay men and lesbians. Evidence is presented that suggests that the Quest Scale and the FDS are measuring different aspects of religious development.     

Disturbed memory and amnesia related to intensive care

Patients, when admitted to an intensive care unit (ICU), have one thing in common: their illness is life-threatening. Patients may remain on ICU in a critical condition, needing support with their breathing, circulation, and/or kidneys for varying lengths of time, from days to weeks. During that time the patients will receive sedative and analgesic drugs to ensure compliance with artificial ventilation. Patients recovering from critical illness frequently have little or no recall of their period in ICU, or remember nightmare, hallucinations, or paranoid delusions. The nature, extent and reason for these difficulties, have been under-reported and consequently our purpose was to conduct a review of memory problems experienced by ICU patients. A systematic literature review of computer databases (Medline, PsycLit, and CINAHL) identified 25 relevant papers. In addition, other relevant articles were obtained, citation lists and associated articles retrieved. Due to lack of research on processes underlying memory problems in ICU patients all articles that introduced an insight into possible mechanisms were included in the review. There seem to be two possible processes contributing to memory problems in ICU patients. First the illness and treatment may have a general dampening effect on memory. Delirium and sleep disturbance are both common in ICU patients. Delirium can result in a profound amnesia for the period of confusion. Sleep deprivation exacerbates the confusional state. Slow wave sleep is important for the consolidation of episodic memories. Treatment administered to patients in ICU can have effects on memory. Opiates, benzodiazepines, sedative drugs such as propofol, adrenaline, and corticosteroids can all influence memory. In addition, the withdrawal of drugs, such as benzodiazepines, can cause profound withdrawal reactions, which may contribute to delirium. Second, we hypothesise that there is a process that affects memory negatively for external events but enhances memory for internal events. The physical constraints and social isolation experienced by ICU patients and the life-threatening nature of the illness may increase the experience of hypnagogic hallucinations. Attentional shift during hypnagogic images from external stimuli to internally generated images would explain why ICU patients have such poor recall of external ICU events, but can clearly remember hallucinations and nightmares. Patients describe these memories as being very vivid and this is explored in terms of flashbulb memory formation. The absence of memories for real events on ICU can result in ICU patients remembering paranoid delusions of staff trying to kill them, with little information to reject these vivid memories as unreal. This has implications for patients' future psychological health.