Transitional and steady-state choice behavior under an adjusting-delay schedule

Twelve rats made repeated choices on an adjusting-delay schedule between a smaller reinforcer (A) that was delivered immediately after a response and a larger reinforcer (B) that was delivered after a delay which increased or decreased by 20% depending on the subject's choices in successive blocks of trials. In two phases of the experiment (100 sessions and 40 sessions), reinforcer sizes were selected which enabled theoretical parameters expressing the rate of delay discounting and sensitivity to reinforcer size to be estimated from the ratio of the indifference delays obtained in the two phases. Indifference delays, calculated from adjusting delays in the last 10 sessions of each phase, were shorter when the sizes of A and B were 14 and 25 μl of a 0.6 M sucrose solution than when they were 25 and 100 μl of the same solution. The ratio of the indifference delays was significantly smaller than that predicted on the basis of an assumed linear relation between reinforcer size and instantaneous reinforcer value, consistent with a previous proposal that this relation may be hyperbolic in form. Estimates of the rate of delay discounting based on the ratio of the two indifference delays (mean, 0.08 s(-1)) were similar to values obtained previously using different intertemporal choice protocols. Estimates of the size-sensitivity parameter (mean 113 μl) were similar to estimates recently derived from performance on progressive-ratio schedules. In both phases of the experiment, adjusting delays in successive blocks of trials were analyzed using the Fourier transform. The power spectrum obtained from individual rats had a dominant frequency that corresponded to a period of oscillation of the adjusting delay between 30 and 100 trial blocks (mean, 78). Power in the dominant frequency band was highest in the early sessions of the first phase and declined with extended training. It is suggested that this experimental protocol may have utility in neurobehavioral studies of intertemporal choice.     

Number of sense effects of Chinese disyllabic compounds in the two hemispheres

The current study manipulated the visual field and the number of senses of the first character in Chinese disyllabic compounds to investigate how the related senses (polysemy) of the constituted character in the compounds were represented and processed in the two hemispheres. The ERP results in experiment 1 revealed crossover patterns in the left hemisphere (LH) and the right hemisphere (RH). The sense facilitation in the LH was in favor of the assumption of single-entry representation for senses. However, the patterns in the RH yielded two possible interpretations: (1) the nature of hemispheric processing in dealing with sublexical sense ambiguity; (2) the semantic activation from the separate-entry representation for senses. To clarify these possibilities, experiment 2 was designed to push participants to a deeper level of lexical processing by the word class judgment. The results revealed the sense facilitation effect in the RH. In sum, the current study was in support of the single-entry account for related senses and demonstrated that two hemispheres processed sublexical sense ambiguity in a complementary way.     

Exploring an integrative model of infant behavior: what is the relationship among temperament, sensory processing, and neurobehavioral measures?

Traditionally, developmental psychology, occupational/physical therapy, and behavioral pediatrics view similar infant behaviors from temperament, sensory processing, or neurobehavioral theoretical perspectives. This study examined the relations between similar and unique summary scores of three infant assessments (Early Infancy Temperament Questionnaire - EITQ, the Infant Sensory Profile - ISP, and the NICU Network Neurobehavioral Scale - NNNS) in a healthy sample of 100, one-month-old infants. A Principal Components Analysis of selected subscale scores derived from the three assessments suggested a three-factor model. Temperament and sensory summary scores had the strongest relations on two factors: Sensory-Affective Reactivity and Engagement. A third factor had strong relations between state regulation and motor competence. This new integrative model also validates an existing model and expands explanation of infant behavior across disciplines and methods which have significant implications for assessment, intervention, and management practices.     

Are historic years understood as numbers or events? An fMRI study of numbers with semantic associations

While numbers generally cue processing of quantity or order, they can also contain semantic information, as in the case of historic years (e.g., “1492” calls forth associations of Columbus sailing the ocean blue). Whether these dates are processed as quantities or events may depend on the context in which they occur. We examined such “ambiguous number” processing in two different contexts using a paired-comparison task, recording both behavioral responses and brain activity. Participants were either asked to think of all items as numbers and to choose the larger number, or were told to treat the comparators as events and to choose the later event. Behaviorally, all events showed a normal distance effect, establishing that they may be understood and compared in an ordinal sequence. Functional magnetic resonance imaging (fMRI) demonstrated significant differences between years when treated as numbers versus as events. Dates in both contexts shared activity in parietal lobe regions previously implicated in number processing. Dates as numbers showed no extra-numeric activity, while dates thought of as events evoked activity in temporal semantic processing and frontal semantic retrieval areas. These differences suggest that extra-numeric information may be easily accessed and incorporated during processing when supported by even a weak context. This work supports previous studies showing a dissociation between quantity and meaning, and illustrates the brain areas involved in these different aspects.     

Does a sensory processing deficit explain counting accuracy on rapid visual sequencing tasks in adults with and without dyslexia?

The experiments conducted aimed to investigate whether reduced accuracy when counting stimuli presented in rapid temporal sequence in adults with dyslexia could be explained by a sensory processing deficit, a general slowing in processing speed or difficulties shifting attention between stimuli. To achieve these aims, the influence of the inter-stimulus interval (ISI), stimulus duration, and sequence length were evaluated in two experiments. In the first that used skilled readers only, significantly more errors were found with presentation of long sequences when the ISI or stimulus durations were short. Experiment 2 used a wider range of ISIs and stimulus durations. Compared to skilled readers, a group with dyslexia had reduced accuracy on two-stimulus sequences when the ISI was short, but not when the ISI was long. Although reduced accuracy was found on all short and long sequences by the group with dyslexia, when performance on two-stimulus sequences was used as an index of sensory processing efficiency and controlled, group differences were found with presentation of stimuli of short duration only. We concluded that continuous, repetitive stimulation to the same visual area can produce a capacity limitation on rapid counting tasks in all readers when the ISIs or stimulus durations are short. While reduced accuracy on rapid sequential counting tasks can be explained by a sensory processing deficit when the stimulus duration is long, slower processing speed in the group with dyslexia explains the greater inaccuracy found as sequence length is increased when the stimulus duration is short.     

Do conscious perception and unconscious processing rely on independent mechanisms? A meta-contrast study

There is currently no consensus regarding what measures are most valid to demonstrate perceptual processing without awareness. Likewise, whether conscious perception and unconscious processing rely on independent mechanisms or lie on a continuum remains a matter of debate. Here, we addressed these issues by comparing the time courses of subjective reports, objective discrimination performance and response priming during meta-contrast masking, under similar attentional demands. We found these to be strikingly similar, suggesting that conscious perception and unconscious processing cannot be dissociated by their time course. Our results also demonstrate that unconscious processing, indexed by response priming, occurs, and that objective discrimination performance indexes the same conscious processes as subjective visibility reports. Finally, our results underscore the role of attention by showing that how much attention the stimulus receives relative to the mask, rather than whether processing is measured by conscious discrimination or by priming, determines the time course of meta-contrast masking.     

The impact of aging and hearing status on verbal short-term memory

The aim of this study is to assess the impact of hearing status on age-related decrease in verbal short-term memory (STM) performance. This was done by administering a battery of verbal STM tasks to elderly and young adult participants matched for hearing thresholds, as well as to young normal-hearing control participants. The matching procedure allowed us to assess the importance of hearing loss as an explanatory factor of age-related STM decline. We observed that elderly participants and hearing-matched young participants showed equal levels of performance in all verbal STM tasks, and performed overall lower than the normal-hearing young control participants. This study provides evidence for recent theoretical accounts considering reduced hearing level as an important explanatory factor of poor auditory-verbal STM performance in older adults.     

Decision-specific reinvestment scale: An exploration of its construct validity,and association with stress and coping appraisals

ObjectiveThis research project aimed to explore the construct validity of the Decision-Specific Reinvestment Scale (DSRS); more specifically, its links with stress and coping appraisals.DesignStudy 1 validated the DSRS and the Movement-Specific Reinvestment Scale (MSRS) to the French language, in order to examine the construct validity of the DSRS using the MSRS, the Preference for Intuition and Deliberation (PID) inventory and the Melbourne Decision-Making Questionnaire (MDMQ). In addition, sex differences in reinvestment were investigated. Study 2 examined stress and coping appraisals of high and low reinvesters.MethodIn study 1, 379 athletes completed the DSRS, MSRS, PID, and MDMQ. In study 2, 100 handball players, classified as low and high reinvesters, completed surveys aimed to assess stressor intensity, stressor perceived controllability, coping effectiveness, subjective performance and coping strategies with the Coping Inventory for Competitive Sport over three games.ResultsIn study 1, we found that intuitive athletes scored lower on the DSRS in comparison to deliberative athletes, whilst no difference was found for the MSRS. Convergent and discriminant validity was illustrated with the subscales of the MDMQ. No sex differences were found regarding reinvestment. In study 2, findings showed that low reinvesters scored higher than high reinvesters in terms of stressor perceived controllability, coping effectiveness and subjective performance.DiscussionIn addition to confirmation of construct validity, these findings strengthen our understanding of how high decision reinvesters perceive a pressured situation. Key applications are derived from our findings informing coaches and athletes in offsetting the negative effects of reinvestment on sport performance.