Identifying expectations about the strength of causal relationships

When we try to identify causal relationships, how strong do we expect that relationship to be? Bayesian models of causal induction rely on assumptions regarding people’s a priori beliefs about causal systems, with recent research focusing on people’s expectations about the strength of causes. These expectations are expressed in terms of prior probability distributions. While proposals about the form of such prior distributions have been made previously, many different distributions are possible, making it difficult to test such proposals exhaustively. In Experiment 1 we used iterated learning—a method in which participants make inferences about data generated based on their own responses in previous trials—to estimate participants’ prior beliefs about the strengths of causes. This method produced estimated prior distributions that were quite different from those previously proposed in the literature. Experiment 2 collected a large set of human judgments on the strength of causal relationships to be used as a benchmark for evaluating different models, using stimuli that cover a wider and more systematic set of contingencies than previous research. Using these judgments, we evaluated the predictions of various Bayesian models. The Bayesian model with priors estimated via iterated learning compared favorably against the others. Experiment 3 estimated participants’ prior beliefs concerning different causal systems, revealing key similarities in their expectations across diverse scenarios.     

The role of eye movements in motor sequence learning

An experiment that utilized a 16-element movement sequence was designed to determine the impact of eye movements on sequence learning. The participants were randomly assigned to two experimental groups: a group that was permitted to use eye movements (FREE) and a second group (FIX) that was instructed to fixate on a marker during acquisition (ACQ). A retention test (RET) was designed to provide a measure of learning, and two transfer tests were designed to determine the extent to which eye movements influenced sequence learning. The results demonstrated that both groups decreased the response time to produce the sequence, but the participants in the FREE group performed the sequence more quickly than participants of the FIX group during the ACQ, RET and the two transfer tests. Furthermore, continuous visual control of response execution was reduced over the course of learning. The results of the transfer tests indicated that oculomotor information regarding the sequence can be stored in memory and enhances response production.     

Evidence of a role for multiple memory systems in behavioral extinction

The acquisition of learned behavior involves multiple memory systems, and hippocampal system damage impairs cognitive learning while leaving stimulus-response habit learning intact. In view of evidence that extinction also involves new learning, the present experiments examined whether multiple memory systems theory may be applicable to the neural bases of extinction. Adult Long-Evans rats were trained to run in a straight-alley maze for food reward. Twenty-four hours later, rats matched for runway latencies during acquisition received extinction training. In a response extinction condition conducive to habit learning, rats performed a runway approach response to an empty food cup. In a latent extinction condition conducive to cognitive learning, rats were placed at an empty food cup without performing a runway approach response. Prior to daily extinction training, neural activity of the dorsal hippocampus was reversibly inactivated via infusion of bupivacaine (0.75%, 0.5 microl/side). Control rats receiving saline infusions displayed extinction behavior in both the response and latent training conditions. In contrast, rats receiving bupivacaine extinguished normally in the response condition, but did not display latent extinction. The findings (1) confirm that learning underlying extinction of the same overt behavior can occur with or without explicit performance of the previously acquired response, (2) indicate that extinction learning produced by response and latent training procedures can be neuroanatomically dissociated, and (3) suggest that similarly to initial task acquisition, the hippocampus may critically mediate extinction in situations requiring the use of cognitive learning, such as when performance of a previously acquired response habit is prevented.     

Developmental study of multiple memory stages in the cuttlefish, Sepia officinalis

The inhibition of predatory behavior observed during the "prawn-in-the-tube" procedure has been extensively used in studies of cuttlefish learning. The present study examines the effect of age on the conditioning of this response in the cuttlefish, Sepia officinalis. Data show that a significant increase in acquisition performance occurs between 15 and 21 days of age. The retention curves in 8- and 15-day-old cuttlefish show a monotonic memory process, presumably reflecting the presence of only short-term memory. In 21-day-old cuttlefish, there are two distinct processes which could be a labile short-term memory, and a subsequent intermediate memory. These mnesic systems seem to become more effective over the course of post-embryonic development. Moreover, the retention curves obtained in the oldest cuttlefish (30- and 90-day-old) bear a close resemblance to that observed in adults. These behavioral findings will allow further work on the cellular and molecular mechanisms of learning and memory in the cuttlefish.     

Satisfiability Decay along Conjunctions of Pseudo-Random Clauses

k-SAT is a fundamental constraint satisfaction problem. It involvesS(m), the satisfaction set of the conjunction of m clauses,each clause a disjunction of k literals. The problem has manytheoretical, algorithmic and practical aspects. When the clauses are chosen at random it is anticipated (butnot fully proven) that, as the density parameter m/n (n thenumber of variables) grows, the transition of S(m) to beingempty, is abrupt: It has a "sharp threshold", with probability1 – o(1). In this article we replace the random ensemble analysis by apseudo-random one: Derive the decay rule for individual sequencesof clauses, subject to combinatorial conditions, which in turnhold with probability 1 – o(1). This is carried out under the big relaxation that k is not constantbut k = log n , or even r log log n . Then the decay of S isslow, "near-perfect" (like a radioactive decay), which entailssharp thresholds for the transition-time of S below any givenlevel, down to S = .     

Imitation: definitions, evidence, and mechanisms

Imitation can be defined as the copying of behavior. To a biologist, interest in imitation is focused on its adaptive value for the survival of the organism, but to a psychologist, the mechanisms responsible for imitation are the most interesting. For psychologists, the most important cases of imitation are those that involve demonstrated behavior that the imitator cannot see when it performs the behavior (e.g., scratching one's head). Such examples of imitation are sometimes referred to as opaque imitation because they are difficult to account for without positing cognitive mechanisms, such as perspective taking, that most animals have not been acknowledged to have. The present review first identifies various forms of social influence and social learning that do not qualify as opaque imitation, including species-typical mechanisms (e.g., mimicry and contagion), motivational mechanisms (e.g., social facilitation, incentive motivation, transfer of fear), attentional mechanisms (e.g., local enhancement, stimulus enhancement), imprinting, following, observational conditioning, and learning how the environment works (affordance learning). It then presents evidence for different forms of opaque imitation in animals, and identifies characteristics of human imitation that have been proposed to distinguish it from animal imitation. Finally, it examines the role played in opaque imitation by demonstrator reinforcement and observer motivation. Although accounts of imitation have been proposed that vary in their level of analysis from neural to cognitive, at present no theory of imitation appears to be adequate to account for the varied results that have been found.     

Are we "experienced listeners"? A review of the musical capacities that do not depend on formal musical training

The present paper reviews a set of studies designed to investigate different aspects of the capacity for processing Western music. This includes perceiving the relationships between a theme and its variations, perceiving musical tensions and relaxations, generating musical expectancies, integrating local structures in large-scale structures, learning new compositional systems and responding to music in an emotional (affective) way. The main focus of these studies was to evaluate the influence of intensive musical training on these capacities. The overall set of data highlights that some musical capacities are acquired through exposure to music without the help of explicit training. These capacities reach such a degree of sophistication that they enable untrained listeners to respond to music as "musically experienced listeners" do.     

Event-related fMRI of category learning: differences in classification and feedback networks

Eighteen healthy young adults underwent event-related (ER) functional magnetic resonance imaging (fMRI) of the brain while performing a visual category learning task. The specific category learning task required subjects to extract the rules that guide classification of quasi-random patterns of dots into categories. Following each classification choice, visual feedback was presented. The average hemodynamic response was calculated across the eighteen subjects to identify the separate networks associated with both classification and feedback. Random-effects analyses identified the different networks implicated during the classification and feedback phases of each trial. The regions included prefrontal cortex, frontal eye fields, supplementary motor and eye fields, thalamus, caudate, superior and inferior parietal lobules, and areas within visual cortex. The differences between classification and feedback were identified as (i) overall higher volumes and signal intensities during classification as compared to feedback, (ii) involvement of the thalamus and superior parietal regions during the classification phase of each trial, and (iii) differential involvement of the caudate head during feedback. The effects of learning were then evaluated for both classification and feedback. Early in learning, subjects showed increased activation in the hippocampal regions during classification and activation in the heads of the caudate nuclei during the corresponding feedback phases. The findings suggest that early stages of prototype-distortion learning are characterized by networks previously associated with strategies of explicit memory and hypothesis testing. However as learning progresses the networks change. This finding suggests that the cognitive strategies also change during prototype-distortion learning.     

A comparison of intra- and inter-limb relative motion information in modelling a novel motor skill

The importance of intra- and inter-limb relative motion in modelling a whole body coordination skill was examined. Participants were assigned to one of four groups: Full-Body point light model of a cricket bowler, INTRA-LIMB relative motion of the bowling arm, INTER-LIMB relative motions of the right and left wrists or NO-Relative motion, showing only the motions of the right wrist. During 60 acquisition trials, participants viewed the model five times before each 10-trial block. Retention was examined the following day. Although all groups improved on intra-limb coordination of the bowling arm, the INTRA-LIMB and FULL-BODY groups were more accurate than the INTER-LIMB group in acquisition, although these groups did not differ in retention. For inter-limb coordination, the three groups who received relative motion information performed more like the model than the NO-Relative motion group (even though the INTRA-LIMB group did not see the other limb). The amount of information within a display plays a constraining role on acquisition, perhaps more so than the type of information, such that the acquisition of coordination is more an emergent feature of observational learning, rather than a direct approximation of the model.     

The role of phonological recoding in orthographic learning

The objective of this research was to explore whether orthographic learning occurs as a result of phonological recoding, as expected from the self-teaching hypothesis. The participants were 32 fourth- and fifth-graders (mean age = 10 years 0 months, SD = 7 months) who performed lexical decisions for monosyllabic real words and pseudowords under two matched experimental conditions: a read aloud condition, wherein items were named prior to lexical decision to promote phonological recoding, and a concurrent articulation condition, presumed to attenuate phonological recoding. Later, orthographic learning of the pseudowords was evaluated using orthographic choice, spelling, and naming tasks. Consistent with the self-teaching hypothesis, targets learned with phonological recoding in the read aloud condition yielded greater orthographic learning than those learned with concurrent articulation. The research confirms the critical nature of phonological recoding in the development of visual word recognition skills and an orthographic lexicon.