The influence of object size and surface shape on shape constancy from stereo

The failure of shape constancy from stereoscopic information is widely reported in the literature. In this study we investigate how shape constancy is influenced by the size of the object and by the shape of the object's surface. Participants performed a shape-judgment task on objects of five sizes with three different surface shapes. The shapes used were: a frontoparallel rectangle, a triangular ridge surface, and a cylindrical surface, all of which contained the same maximum depth information, but different variations in depth across the surface. The results showed that, generally, small objects appear stretched and large objects appear squashed along the depth dimension. We also found a larger variance in shape judgments for rectangular stimuli than for cylindrical and ridge-shaped stimuli, suggesting that, when performing shape judgments with cylindrical and ridge-shaped stimuli, observers rely on a higher-order shape representation.     

The effects of frequency and predictability on eye fixations in reading: implications for the E-Z Reader model

Readers read sentences containing target words varying in frequency and predictability. The observed pattern of data for fixation durations only mildly departed from additivity, with predictability effects that were slightly larger for low-frequency than for high-frequency words. The pattern of data for skipping was different as predictability affected only the probability of skipping for high-frequency target words. Simulations of these data using the E-Z Reader model indicated that a single-process model was unlikely to provide a good fit for both measures. A version of the model that assumes that (a) word-encoding time is additively affected by frequency and predictability and (b) difficulty with postlexical processing of the target word causes a double take accounted for the data while indicating that the relationship between the duration of hypothesized word-encoding stages and observed fixation durations is not likely to be transparent.     

Is unconscious identity priming lexical or sublexical?

We examined unconscious priming in a stem-completion task with both identity and form-related primes. Participants were given exclusion instructions to avoid completing a stem (e.g., ca---) with a briefly flashed masked word (e.g., candy). In Experiment 1, priming of around 7% occurred for both identity (e.g., candy) and form-based (e.g., windy) primes at a 33 ms exposure duration. When examining only trials in which the participants failed to identify the prime, this effect increased to 12% for identity primes, but remained the same for form-based primes. In Experiment 2, priming without prime identification was 9% for identity primes, 4% for homophone primes, and 3% for orthographic control primes. Although identity priming was greater than form priming in both experiments, regression analyses revealed that orthographic and phonological overlap alone between the flashed primes and targets could completely account for unconscious identity priming. Hence, we conclude that masked words may only activate their sublexical orthographic and phonological representations and not their lexical representations.     

Self-cutting: patient characteristics compared with self-poisoners

A large ( n = 14,892) consecutive sample of deliberate self-harm (attempted suicide) patients who presented to a general hospital in the United Kingdom during a 23-year study period was examined (over two consecutive time periods) in order to compare the characteristics of those who used self-cutting ( n = 428) and those who self-poisoned ( n = 11,065). Patients who used different methods on other occasions, or were not assessed by the psychiatric service, were excluded. In the first time period (January 1976-June 1988), the self-cutters were distinguished from the self-poisoners by more often being male, single, not employed, and having a history of previous deliberate self-harm. In the second time period (July 1988-December 1998) the self-cutters were again distinguished by more often being male and having a history of previous deliberate self-harm, but also by being more likely to live alone, misuse alcohol, and have low suicidal intent scores. The finding of an excess of males among the self-cutters is contrary to the impression in the literature that self-cutting presentations to general hospitals more often involve females. It also indicates that the treatment needs of those who deliberately cut themselves are likely to differ from those of self-poisoners.     

Extinction training regulates neuroadaptive responses to withdrawal from chronic cocaine self-administration

Cocaine produces multiple neuroadaptations with chronic repeated use. Many of these neuroadaptations can be reversed or normalized by extinction training during withdrawal from chronic cocaine self-administration in rats. This article reviews our past and present studies on extinction-induced modulation of the neuroadaptive response to chronic cocaine in the mesolimbic dopamine system, and the role of this modulation in addictive behavior in rats. Extinction training normalizes tyrosine hydroxylase levels in the nucleus accumbens (NAc) shell, an effect that could help ameliorate dysphoria and depression associated with withdrawal from chronic cocaine use. Extinction training also increases levels of GluR1 and GluR2/3 AMPA receptor subunits, while normalizing deficits in NR1 NMDA receptor subunits, in a manner consistent with long-term potentiation of excitatory synapses in the NAc shell. Our results suggest that extinction-induced increases in AMPA and NMDA receptors may restore deficits in cortico-accumbal neurotransmission in the NAc shell and facilitate inhibitory control over cocaine-seeking behavior. Other changes identified by gene expression profiling, including up-regulation in the AMPA receptor aggregating protein Narp, suggest that extinction training induces extensive synaptic reorganization. These studies highlight potential benefits for extinction training procedures in the treatment of drug addiction.     

Neurobiological and endocrine correlates of individual differences in spatial learning ability

The polysialylated neural cell adhesion molecule (PSA-NCAM) has been implicated in activity-dependent synaptic remodeling and memory formation. Here, we questioned whether training-induced modulation of PSA-NCAM expression might be related to individual differences in spatial learning abilities. At 12 h posttraining, immunohistochemical analyses revealed a learning-induced up-regulation of PSA-NCAM in the hippocampal dentate gyrus that was related to the spatial learning abilities displayed by rats during training. Specifically, a positive correlation was found between latency to find the platform and subsequent activated PSA levels, indicating that greater induction of polysialylation was observed in rats with the slower acquisition curve. At posttraining times when no learning-associated activation of PSA was observed, no such correlation was found. Further experiments revealed that performance in the massed water maze training is related to a pattern of spatial learning and memory abilities, and to learning-related glucocorticoid responsiveness. Taken together, our findings suggest that the learning-related neural circuits of fast learners are better suited to solving the water maze task than those of slow learners, the latter relying more on structural reorganization to form memory, rather than the relatively economic mechanism of altering synaptic efficacy that is likely used by the former.     

Recent advances in operant conditioning technology: A versatile and affordable computerized touchscreen system

We report the construction of a new operant chamber that incorporates modern computer, touchscreen, and display technologies. An LCD display was housed in the front wall of a lightweight Plexiglas chamber. An Apple eMac computer was used to present visual stimuli on the monitor and to control other chamber events. Responses to the stimuli were recorded using a transparent resistive-type touchscreen that overlaid the monitor. The resulting system is simple and inexpensive to construct but powerful and flexible enough to explore a broad range of issues in animal learning and behavior.     

Presleep attributions about arousal during sleep: nocturnal panic

This study examined the role of presleep attributions about physiological events during sleep in nocturnal panic attacks. Patients who regularly experienced nocturnal panic were physiologically monitored as audio signals were presented during sleep. They were randomly assigned to 1 of 3 conditions: expected, in which signals of intense physiological changes were expected; unexpected, in which signals of intense physiological changes were not expected; or control, involving distinctly different signals unrelated to physiological responses. The unexpected condition led to substantially more self-reported distress and panic attacks. The experimental conditions did not elicit different autonomic reactions, but those who panicked showed stronger physiological responses than those who did not panic. The findings are consistent with a cognitive model of nocturnal panic attacks.     

Comparing techniques for estimating automatic retrieval: effects of retention interval

Results from implicit memory (IM) tasks suggest that automatic retrieval remains stable or decreases over time. In contrast, results from the process dissociation approach (PDA) suggest that automatic retrieval may actually increase over time. One explanation for these discrepant results is that performance on IM tasks is contaminated by controlled retrieval strategies, thereby overestimating automatic retrieval, particularly at short retention intervals, when controlled retrieval strategies are high. An alternative explanation is that automatic and controlled retrieval are positively correlated, rather than independent as assumed by the PDA. If so, the PDA would underestimate automatic retrieval, particularly when controlled retrieval strategies are high. Results from a speeded IM task suggest that a standard IM task provided an accurate estimate of automatic retrieval, whereas the PDA underestimated automatic retrieval at a short retention interval. This pattern of underestimation by the PDA supports the conclusion that automatic and controlled retrieval were positively correlated rather than independent.     

Using culturally sensitive theories and research to meet the academic needs of low-income African American children

The economic and social barriers to the academic and social success of many African American children remain in place as the new millennium begins. These realities provide impetus for developing community-based partnership education programs designed to self-empower African American children for academic and social success under any socioeconomic conditions that exist in their lives. Progress toward effective program development, however, has been hindered by a dearth of culturally sensitive theories and research. The Research-Based Model Partnership Education Program (Model Program) is an effective, community-based, university-school-community partnership education program for self-empowering African American children for success. The formative and summative research of the Model Program is described in hopes of advancing theory and research for meeting the academic and social needs of low-income African American children.