Surprise! Infants consider possible bases of generalization for a single input example

Infants have been shown to generalize from a small number of input examples. However, existing studies allow two possible means of generalization. One is via a process of noting similarities shared by several examples. Alternatively, generalization may reflect an implicit desire to explain the input. The latter view suggests that generalization might occur when even a single input example is surprising, given the learner's current model of the domain. To test the possibility that infants are able to generalize based on a single example, we familiarized 9‐month‐olds with a single three‐syllable input example that contained either one surprising feature (syllable repetition, Experiment 1) or two features (repetition and a rare syllable, Experiment 2). In both experiments, infants generalized only to new strings that maintained all of the surprising features from familiarization. This research suggests that surprise can promote very rapid generalization.     

Warrant and action

I develop an approach to action and practical deliberation according to which the degree of epistemic warrant required for practical rationality varies with practical context. In some contexts of practical deliberation, very strong warrant is called for. In others, less will do. I set forth a warrant account, (WA), that captures this idea. I develop and defend (WA) by arguing that it is more promising than a competing knowledge account of action due to John Hawthorne and Jason Stanley. I argue that cases of warranted false belief speak in favor of (WA) and against the knowledge account. Moreover, I note some problems with an “excuse maneuver” that proponents of the knowledge account frequently invoke in response to cases of warranted false belief. Finally, I argue that (WA) may provide a strict invariantist account of cases that have been thought to motivate interest-relative or subject-sensitive theories of knowledge and warrant.     

When global structure "Explains Away" local grammar: a Bayesian account of rule-induction in tone sequences

While many constraints on learning must be relatively experience-independent, past experience provides a rich source of guidance for subsequent learning. Discovering structure in some domain can inform a learner’s future hypotheses about that domain. If a general property accounts for particular sub-patterns, a rational learner should not stipulate separate explanations for each detail without additional evidence, as the general structure has “explained away” the original evidence. In a grammar-learning experiment using tone sequences, manipulating learners’ prior exposure to a tone environment affects their sensitivity to the grammar-defining feature, in this case consecutive repeated tones. Grammar-learning performance is worse if context melodies are “smooth” — when small intervals occur more than large ones — as Smoothness is a general property accounting for a high rate of repetition. We present an idealized Bayesian model as a “best case” benchmark for learning repetition grammars. When context melodies are Smooth, the model places greater weight on the small-interval constraint, and does not learn the repetition rule as well as when context melodies are not Smooth, paralleling the human learners. These findings support an account of abstract grammar-induction in which learners rationally assess the statistical evidence for underlying structure based on a generative model of the environment.     

Statistical frequency in perception affects children’s lexical production

Children’s early word production is influenced by the statistical frequency of speech sounds and combinations. Three experiments asked whether this production effect can be explained by a perceptual learning mechanism that is sensitive to word-token frequency and/or variability. Four-year-olds were exposed to nonwords that were either frequent (presented 10 times) or infrequent (presented once). When the frequent nonwords were spoken by the same talker, children showed no significant effect of perceptual frequency on production. When the frequent nonwords were spoken by different talkers, children produced them with fewer errors and shorter latencies. The results implicate token variability in perceptual learning.     

Truth-Sensitivity and Folk Epistemology

Several studies have found a robust effect of truth on epistemic evaluation of belief, decision, action and assertion. Thus, truth has a significant effect on normative participant evaluations. Some theorists take this truth effect to motivate factive epistemic norms of belief, action, assertion etc. In contrast, I argue that the truth effect is best understood as an epistemic instance of the familiar and ubiquitous phenomenon of outcome bias. I support this diagnosis from three interrelating perspectives: (1) by epistemological theorizing, (2) by considerations from cognitive psychology and (3) by methodological reflections on the relationship between folk epistemology and epistemological theorizing.     

Discursive justification and skepticism

In this paper, I consider how a general epistemic norm of action that I have proposed in earlier work should be specified in order to govern certain types of acts: assertive speech acts. More specifically, I argue that the epistemic norm of assertion is structurally similar to the epistemic norm of action. First, I argue that the notion of warrant operative in the epistemic norm of a central type of assertion is an internalist one that I call ??discursive justification.?? This type of warrant is internalist insofar as it requires that the agent is capable of articulating reasons for her belief. The idea, roughly, is that when one asserts that p, one is supposed to be in a position to give reasons for believing that p. Bonjour??s reliable clairvoyant Norman, for example, is not in an epistemic position to make assertions regarding the president??s whereabouts??even if Norman knows the president??s whereabouts. In conclusion, I briefly consider whether a type of skeptical argument??often labeled Agrippa??s Trilemma??is motivated, at least in part, by the fact that responses to it violate the relevant epistemic norm of assertion.     

Detection by the guinea pig of acoustic stimulation and of electrical stimulation of the brain

A threshold procedure using operant behavioral techniques with positive reinforcement was developed after initial efforts with avoidance behavioral procedures proved unsatisfactory. In the first of three experiments the operant threshold procedure was tested by determining masked auditory thresholds for trains of clicks. In a second experiment, similar techniques were used to measure thresholds for electrical stimulation of the brain. The last experiment, again an auditory problem, involved a determination of the absolute thresholds for trains of short noise bursts as a function of the time between bursts. Middle ear malfunction proved to be a more severe problem than had been anticipated on the basis of reports in the literature. The threshold procedure, however, seems to be adequate for determination of absolute or masked thresholds with auditory or electrical stimuli.     

Perceived effectiveness of school psychological services: A comparative study

In order to isolate variables present in school psychologists which may enhance effective delivery of school psychological service, supervisors of psychological services, classroom teachers, and building principals within the state of Iowa were asked to evaluate the performance of their school psychologist in 10 functional areas. Both supervisors and classroom teachers perceived those school psychologists with 4–9 years experience as the most effective. Teaching experience, as a requirement for school psychology certification, did not receive support. The level of training for the psychologist (degree) yielded conflicting results among the raters.     

Infant sensitivity to distributional information can affect phonetic discrimination.

For nearly two decades it has been known that infants' perception of speech sounds is affected by native language input during the first year of life. However, definitive evidence of a mechanism to explain these developmental changes in speech perception has remained elusive. The present study provides the first evidence for such a mechanism, showing that the statistical distribution of phonetic variation in the speech signal influences whether 6- and 8-month-old infants discriminate a pair of speech sounds. We familiarized infants with speech sounds from a phonetic continuum, exhibiting either a bimodal or unimodal frequency distribution. During the test phase, only infants in the bimodal condition discriminated tokens from the endpoints of the continuum. These results demonstrate that infants are sensitive to the statistical distribution of speech sounds in the input language, and that this sensitivity influences speech perception.