The stereoscopic anisotropy: individual differences and underlying mechanisms

Observers are more sensitive to variations in the depth of stereoscopic surfaces in a vertical than in a horizontal direction; however, there are large individual differences in this anisotropy. The authors measured discrimination thresholds for surfaces slanted about a vertical axis or inclined about a horizontal axis for 50 observers. Orientation and spatial frequency discrimination thresholds were also measured. For most observers, thresholds were lower for inclination than for slant and lower for orientation than for spatial frequency. There was a positive correlation between the 2 anisotropies, resulting from positive correlations between (a) orientation and inclination thresholds and (b) spatial frequency and slant thresholds. These results support the notion that surface inclination and slant perception is in part limited by the sensitivity of orientation and spatial frequency mechanisms.     

Orthographic learning during reading: examining the role of self-teaching

Thirty-four second grade children read target homophonic pseudowords (e.g., slurst/slirst) in the context of real stories in a test of the self-teaching theory of early reading acquisition. The degree of orthographic learning was assessed with three converging tasks: homophonic choice, spelling, and target naming. Each of the tasks indicated that orthographic learning had taken place because processing of target homophones (e.g., yait) was superior to that of their homophonic controls (e.g., yate). Consistent with the self-teaching hypothesis, we obtained a substantial correlation (r=.52) between orthographic learning and the number of target homophones correctly decoded during story reading. Hierarchical multiple regression analyses indicated that neither RAN tasks nor general cognitive ability predicted variance in orthographic learning once the number of target homophones correctly decoded during story reading had been partialed out. In contrast, a measure of orthographic knowledge predicted variance in orthographic learning once the number of targets correctly decoded had been partialed. The development of orthographic knowledge appears to be not entirely parasitic on decoding ability. (c) 2002 Elsevier Science (USA).     

Category-specific naming and modality-specific imagery

Some attempts to explain category-specific disorders have stressed how different modality knowledge bases (i.e., visual knowledge vs motoric/functional knowledge) may underlie the distinction between living and nonliving things. This study examined 60 normal subjects for the relationship between picture naming in four subcategories (animals, fruit/vegetables, praxic and nonpraxic objects) and imagery vividness in seven modalities. Participants made more nonliving than living errors; and females made more nonliving errors than males. There was a significant correlation between naming of animals and fruits/vegetables and visual imagery vividness; however, this association was also significant for praxic and nonpraxic object naming. There was no evidence of associations between kinesthetic imagery and praxic object naming or gustatory/olfactory imagery and fruit/vegetable naming. These findings accord with the notion of a general association between visual imagery and picture naming, but provide no support for more specific links between modality-specific imagery vividness and naming in different categories.     

Interpretative memories of artworks

It is well known that memories of self-relevant experiences are reconstructed over time. Artworks often require an elongated period of interpretative meaning-making. Such works were therefore used to study temporal aspects of memory construction. In a longitudinal study, individuals' memories of artworks were examined to explore the idea that only with the passage of time would autobiographical memory and emotion be associated with thematic integration of the artwork memory. We also expected that integrated artwork memories would be more differentiated (in terms of number of details) than memories that were not integrated. Memories of artworks were collected from visitors to an art gallery in person as they left the gallery, and 5 months later in a phone interview. Participants were also asked, at both interviews, whether the memory recollection was associated with an autobiographical memory and with an emotion. Associations among the elements of autobiographical memory, emotion, differentiation, and integrated artwork memories were significant only at the time of the longer-term recollection. The data suggest that, during an incubation period, these elements moved from a state of disconnection to interconnection.     

Construction of preferences by constraint satisfaction

Participants were given a choice between two multiattribute alternatives (job offers). Preferences for the attributes were measured before, during, and after the choices were made. We found that over the course of decision making, the preferences shifted to cohere with the choice: The attributes of the option that was eventually chosen came to be rated more favorably than they had been rated initially, while the attributes of the rejected option received lower preference ratings than before. These coherence shifts were triggered by a single attribute that decisively favored one option (Experiment 1), and occurred spontaneously in the absence of a decisive attribute (Experiment 2). The coherence shift preceded commitment to choice. These findings favor constraint-satisfaction models of decision making.     

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.     

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.