Badgers were sampled once during the sexually inactive season (July-November) and during the breeding season (February-April) and testosterone and dihydrotestosterone (DHT) concentrations were measured by radioimmunoassay after separation by chromatography. Concentrations of both hormones were higher in the breeding than non-breeding season, but the mean ratio of testosterone to DHT was greater...

The study objective was to determine the effect of chlortetracycline in an ad libitum trace-mineralized salt mix given to heifers before and(or) during bull exposure on the proportion pregnant and the time to conception in a fixed breeding period. Heifers (n = 768), 13 to 15 mo of age, were individually identified, immunized (Leptospira, Campylobacter fetus), examined (body condition score, vag...

In colonial breeding species, preventive measures to reduce the risks of extra-pair copulations (EPCs) should reflect the actual risk perceived by males (e.g., proximity of neighbors, intrusions into the nest) mainly during the fertile period. In colonial vultures, specific studies examining the preventive measures that minimize the risks of EPCs occurring within the competitive context of colo...

In a parity judgment task, the ERPs at parietal electrode sites become more negative as more mental rotation has to be executed. This article provides a review of the empirical evidence regarding this amplitude modulation. More specifically, experiments are reported that validate both the functional relationship between mental rotation and the amplitude modulation as well as the temporal relati...

We investigated whether concurrent processing of a tone (T1) interferes with early sensory-perceptual processing of a visual target (T2) in variants of the psychological refractory period paradigm using the event-related potential (ERP) method and 70-channel electroencephalographic recordings. T1, which required a speeded response, was presented in all trials. In half of the trials, T1 was foll...

M. A. Van Selst, E. Ruthruff, and J. C. Johnston (1999) found that practice dramatically reduced dual-task interference in a Psychological Refractory Period (PRP) paradigm with 1 vocal response and 1 manual response. Results from 3 further experiments using the highly trained participants of M. A. Van Selst et al. (1999) support 4 main conclusions: (a) A processing bottleneck exists even after ...

The apparently deleterious effect of aging on dual-task performance is well established, but there is little agreement about the source of this effect. Studies of the psychological refractory period (PRP) indicate that young adults can flexibly control dual-task performance through task-coordination strategies. Thus, the performance of older adults might differ from young adults because older a...

Why is the human brain fundamentally limited when attempting to execute two tasks at the same time or in close succession? Two classical paradigms, psychological refractory period (PRP) and task switching, have independently approached this issue, making significant advances in our understanding of the architecture of cognition. Yet, there is an apparent contradiction between the conclusions de...

introduction agricultural research is important and one of the determinant factors of development of technologies in agricultural sector. among agricultural research disciplines, breeding programs, especially, wheat breeding programs are one of the applied approaches in improving of production and food security. based on a study by byerlee & traxler (1995), economic benefits and internal rate o...