Rule learning by cotton-top tamarins

Previous work suggests that human infants are capable of rapidly generalizing patterns that have been characterized as abstract algebraic rules (Science 283 (1999) 77), a process that may play a pivotal role in language acquisition. Here we explore whether this capacity is uniquely human and evolved specifically for the computational problems associated with language, or whether this mechanism is shared with other species, and therefore evolved for problems other than language. We used the same materials and methods that were originally employed in tests of human infants to assess whether cotton-top tamarin monkeys can extract abstract algebraic rules. Specifically, we habituated subjects to sequences of consonant-vowel syllables that followed one of two patterns, AAB (e.g. wi wi di) or ABB (le we we). Following habituation, we presented subjects with two novel test items, one with the same pattern as that presented during habituation and one with a different pattern. Like human infants, tamarins were more likely to dishabituate to the test item with a different pattern. We conclude that the capacity to generalize rule-like patterns, at least at the level demonstrated, did not evolve specifically for language acquisition, though it remains possible that infants might use such rules during language acquisition.     

Age-related susceptibility to the Müller-Lyer and the horizontal-vertical illusions

Participants between the ages of 3 and 20 years adjusted the Müller-Lyer illusion and the inverted-T form of the Horizontal-Vertical illusion. Perceptual error was quantified using signal detection and nonparametric measures of sensitivity and responsivity. Significant changes in sensitivity and responsivity were found for each illusion across participants' ages. No effect of sex of participant was found. Sensitivity and responsivity were largely asymptotic between the ages of 13 to 15 years for the Müller-Lyer illusion and between the ages of 11 to 15 years for the Horizontal-Vertical illusion.     

Dissymmetry and Height: Rhetoric, Irony and Pedagogy in the Thought of Husserl, Blanchot and Levinas

This essay is concerned with an initial mapping out of a model of intersubjectivity that, viewed within the context of education, breaks with the hegemonic dialogics of current pedagogies. Intent on rethinking the (so-called)problem of solipsism for phenomenology in terms of a pedagogy that situates itself within solitude and the alterity of self and other, Maurice Blanchot and Emmanuel Levinas will here speak as the voices of this other mode of teaching. Beginning with the problematization of intersubjectivity in romantic aesthetics and hermeneutics, I introduce the concept of irony as a crucial element in the conceptualization of this other pedagogical model, one that requires, initially, a discussion of Husserl's response to the charge of solipsism in the 5th Cartesian Meditation. As a starting point I introduce his symmetrical notion of bodily pairing into a consideration of rhetoric, understood here as an integral part of teaching, thus forging links with phenomenology via the work of Merleau-Ponty. The above provides a context for an extended discussion of pedagogy as it appears in the work of Blanchot and Levinas. Although similar in many respects, on closer inspection it will emerge that important differences are evident in the dissymmetrical and asymmetrical models suggested by the two thinkers respectively. These differences, I will argue, begin to open up a critical perspective on Levinas' height model of teaching in the name of the more radical configuration of phenomenology and rhetoric to be found in Blanchot.     

Judging egocentric distance on the ground: occlusion and surface integration

On the basis of the finding that a common and homogeneous ground surface is vital for accurate egocentric distance judgments (Sinai et al, 1998 Nature 395 497-500), we propose a sequential-surface-integration-process (SSIP) hypothesis to elucidate how the visual system constructs a representation of the ground-surface in the intermediate distance range. According to the SSIP hypothesis, a near ground-surface representation is formed from near depth cues, and is utilized as an anchor to integrate the more distant surfaces by using texture-gradient information as the depth cue. The SSIP hypothesis provides an explanation for the finding that egocentric distance judgment is underestimated when a texture boundary exists on the ground surface that commonly supports the observer and target. We tested the prediction that the fidelity of the visually represented ground-surface reference frame depends on how the visual system selects the surface information for integration. Specifically, if information is selected along a direct route between the observer and target where the ground surface is disrupted by an occluding object, the ground surface will be inaccurately represented. In experiments 1-3 we used a perceptual task and two different visually directed tasks to show that this leads to egocentric distance underestimation. Judgment is accurate however, when the observer selects the continuous ground information bypassing the occluding object (indirect route), as found in experiments 4 and 5 with a visually directed task. Altogether, our findings provide support for the SSIP hypothesis and reveal, surprisingly, that the phenomenal visual space is not unique but depends on how optic information is selected.     

Temporal stability of WISC-III subtest composite: strengths and weaknesses

The Wechsler Intelligence Scale for Children--Third Edition (D. Wechsler, 1991; WISC-III) is often used to identify subtest-based cognitive strengths and weaknesses that are subsequently used to generate interventions. Given that intelligence is presumed to be an enduring trait, cognitive strengths and weaknesses identified via subtest analysis should also be stable over time. This was evaluated with 579 students who were twice tested with the WISC-III. Based on 66 subtest composites, 6 or 7 interpretable cognitive strengths and weaknesses were found on each WISC-III administration. However, subtest-based strengths and weaknesses replicated across test-retest occasions at chance levels. Because subtest-based cognitive strengths and weaknesses are unreliable, recommendations based on them will also be unreliable.     

Hippocampal sharp wave bursts coincide with neocortical "up-state" transitions

The sleeping neocortex shows nested oscillatory activity in different frequency ranges, characterized by fluctuations between "up-states" and "down-states." High-density neuronal ensemble recordings in rats now reveal the interaction between synchronized activity in the hippocampus and neocortex: Electroencephalographic sharp waves in the hippocampus were more probable during down-states than during up-states, and tended to coincide with transitions from down-states to up-states. The form of cortical activity fluctuations and their interactions with sharp waves depend on sleep depth: In deeper sleep stages, characterized by strong neocortical oscillation in the delta range or slower (approximately 0.8-4 Hz), sharp-wave-triggered peri-event time histograms (PETH) are consistent with a longer duration for down-states than for up-states. In lighter sleep, the sharp-wave-triggered PETH suggested longer up-states than down-states. These results highlight the interplay in the hippocampal/neocortical loop: Decreased neocortical input during down-states may be a factor in generation of sharp waves. In turn, sharp waves may facilitate down-to-up transitions. This interplay may reflect joint memory trace reactivation in the hippocampus and in the neocortex, possibly contributing to consolidation of long-term memory: Off-line reactivation of recent neural activity patterns in the hippocampus occurs during 50-100-msec electroencephalographic sharp waves, corresponding to pyramidal-cell population bursts. The neocortical up-states starting in correspondence with sharp waves may be influenced by the reactivated information carried by the hippocampal sharp wave.     

Eyewitness identification accuracy and response latency: the unruly 10-12-second rule

Data are reported from 3,213 research eyewitnesses confirming that accurate eyewitness identifications from lineups are made faster than are inaccurate identifications. However, consistent with predictions from the recognition and search literatures, the authors did not find support for the "10-12-s rule" in which lineup identifications faster than 10-12 s maximally discriminate between accurate and inaccurate identifications (D. Dunning & S. Perretta, 2002). Instead, the time frame that proved most discriminating was highly variable across experiments, ranging from 5 s to 29 s, and the maximally discriminating time was often unimpressive in its ability to sort accurate from inaccurate identifications. The authors suggest several factors that are likely to moderate the 10-12-s rule.     

The fragile X syndrome: from molecular genetics to neurobiology

Since the identification of the FMR1 gene basic research has been focused on the molecular characterization of the FMR1 gene product, the fragile X mental retardation protein (FMRP). Recent developments in fragile X research have provided new insights and knowledge about the physiological function of FMRP in the cell and the nerve cell in particular. Currently, compelling evidence suggests a role for FMRP in the transport/translation of dendritically localized mRNAs. In addition, the identification of some of the target mRNAs of FMRP have led to an increased interest in the neurobiology of the syndrome. This review highlights the role of FMRP in dendritic mRNA transport/translation in relation to synaptic plasticity, a molecular mechanism implicated in learning and memory.