Development of object permanence in food-storing magpies (Pica pica)

The development of object permanence was investigated in black-billed magpies (Pica pica), a food-storing passerine bird. The authors tested the hypothesis that food-storing development should be correlated with object-permanence development and that specific stages of object permanence should be achieved before magpies become independent. As predicted, Piagetian Stages 4 and 5 were reached before independence was achieved, and the ability to represent a fully hidden object (Piagetian Stage 4) emerged by the age when magpies begin to retrieve food. Contrary to psittacine birds and humans, but as in dogs and cats, no "A-not-B error" occurred. Although magpies also mastered 5 of 6 invisible displacement tasks, evidence of Piagetian Stage 6 competence was ambiguous.     

Family functioning and early onset of sexual intercourse in Latino adolescents

The purpose of this study was to identify factors associated with early onset of sexual intercourse. Within an ecological system's conceptual framework, familial factors associated with early onset of sexual activity were identified in a sample of 425 adolescents from San Juan metro area schools. Measures included questions about sexual activity, sexual permissiveness, and such familial variables as: discipline, parental supervision, and parental support. Significant relationships were observed between early onset of sexual intercourse and parental supervision, discipline, parental support, and parents' marital status. Results suggest the key role of parents and family in prevention of HIV-risk behaviors among adolescents in terms of delaying sexual onset. Overall, the study described youths who postponed sexual activity as having greater support, supervision, and parental involvement.     

Intention memory and achievement motivation: volitional facilitation and inhibition as a function of affective contents of need-related stimuli

Replicating findings of J. Kuhl and M. Kazén (1999), reduction or removal of Stroop interference was achieved after short exposure to primes eliciting positive affect. This effect was need specific: Stroop interference removal (volitional facilitation) was found with positive primes related to achievement needs but not with positive primes related to affiliation or power needs. Five studies are reported. College students and unemployed university graduates participated in 2 studies each and branch managers of a large insurance company in 1 study. Whereas Stroop interference reduction or removal was found in all groups after positive-achievement primes, the 2 groups of unemployed persons additionally showed a significant increase of Stroop interference (volitional inhibition) after exposure to primes related to negative achievement episodes. Results are discussed in the context of Kuhl's personality systems interactions theory.     

Neural correlates of a default response in a delayed go/no-go task

Working memory, the ability to temporarily retain task-relevant information across a delay, is frequently investigated using delayed matching-to-sample (DMTS) or delayed Go/No-Go tasks (DGNG). In DMTS tasks, sample cues instruct the animal which type of response has to be executed at the end of a delay. Typically, performance decreases with increasing delay duration, indicating that working memory fades across a delay. However, no such performance decrease has been found when the sample cues exist of present vs. absent stimuli, suggesting that pigeons do not rely on working memory, but seem to respond by default in those trials. We trained 3 pigeons in a DGNG task and found a similar default response pattern: The diverging slopes of the retention functions on correct Go and No-Go trials suggested that pigeons by default omitted their response following No-Go stimuli, but actively retained task-relevant information across the delay for successful responses on Go trials. We conducted single-cell recordings in the avian nidopallium caudolaterale, a structure comparable to the mammalian prefrontal cortex. On Go trials, many neurons displayed sustained elevated activity during the delay preceding the response, replicating previous findings and suggesting that task-relevant information was neurally represented and maintained across the delay. However, the same units did not show enhanced delay activity preceding correct response suppressions in No-Go trials. This activation-inactivation pattern presumably constitutes a neural correlate of the default response strategy observed in the DGNG task.     

The frequency effect for pseudowords in the lexical decision task

Four experiments were designed to investigate whether the frequency of words used to create pseudowords plays an important role in lexical decision. Computational models of the lexical decision task (e.g., the dual route cascaded model and the multiple read-out model) predict that latencies to low-frequency pseudowords should be faster than latencies to high-frequency pseudowords. Consistent with this prediction, results showed that when the pseudowords were created by replacing one internal letter of the base word (Experiments 1 and 3), high-frequency pseudowords yielded slower latencies than low-frequency pseudowords. However, this effect occurred only in the leading edge of the response time (RT) distributions. When the pseudowords were created by transposing two adjacent internal letters (Experiment 2), high-frequency pseudowords produced slower latencies in the leading edge and in the bulk of the RT distributions. These results suggest that transposed-letter pseudowords may be more similar to their base words than replacement-letter pseudowords. Finally, when participants performed a go/no-go lexical decision task with one-letter different pseudowords (Experiment 4), high-frequency pseudowords yielded substantially faster latencies than low-frequency pseudowords, which suggests that the lexical entries of high-frequency words can be verified earlier than the lexical entries of low-frequency words. The implications of these results for models of word recognition and lexical decision are discussed.     

Statistical computations over a speech stream in a rodent

Statistical learning is one of the key mechanisms available to human infants and adults when they face the problems of segmenting a speech stream (Saffran, Aslin, & Newport, 1996) and extracting long-distance regularities (G6mez, 2002; Pe?a, Bonatti, Nespor, & Mehler, 2002). In the present study, we explore statistical learning abilities in rats in the context of speech segmentation experiments. In a series of five experiments, we address whether rats can compute the necessary statistics to be able to segment synthesized speech streams and detect regularities associated with grammatical structures. Our results demonstrate that rats can segment the streams using the frequency of co-occurrence (not transitional probabilities, as human infants do) among items, showing that some basic statistical learning mechanism generalizes over nonprimate species. Nevertheless, rats did not differentiate among test items when the stream was organized over more complex regularities that involved nonadjacent elements and abstract grammar-like rules.     

Body mass index in female Spanish Olympic athletes

The purpose of this study was to examine the Body Mass Index of 180 female Spanish Olympic athletes (M age = 27.1 yr., SD = 5.9 yr.) who participate in presentation sports and nonpresentation sports, in comparison with 114 female nonathletes (M age = 20.7, SD = 1.5 yr.). Presentation sports athletes have a profile similar to that of a university student but by age with a lower Body Mass Index. In particular, rhythmic gymnasts have a lower weight and Body Mass Index than other athletes and nonathletes.     

Early psychological consequences of the March 11, 2004, terrorist attacks in Madrid, Spain

On March 11, 2004, Al-Qaeda set off 10 bombs on several train routes in Madrid. 192 people were killed and 2,000 wounded. In this study, 1,179 questionnaires were administered Week 2 after the attacks to residents 18 years and over from the affected geographical areas. The questionnaire included items about sociodemographic variables and exposure to the attacks. Psychological effects were assessed as presence of acute stress and depressive symptomatology and functional impairment. 46.7% of the sample presented symptomatology of acute stress and 49.6% depressive symptoms. Among the symptoms of acute stress, the most frequent were re-experiencing (72.5%) and dissociative symptoms (71.8%). The chief predicting variables in symptomatology were being female, over 65 yr. old, and a habitual train user. The large number of affected people was refined with an item analysis and the consideration of severity of interference in psychosocial functioning.