Dynamical age differences among coeval star clusters as revealed by blue stragglers.

Globular star clusters that formed at the same cosmic time may have evolved rather differently from the dynamical point of view (because that evolution depends on the internal environment) through a variety of processes that tend progressively to segregate stars more massive than the average towards the cluster centre. Therefore clusters with the same chronological age may have reached quite different stages of their dynamical history (that is, they may have different 'dynamical ages'). Blue straggler stars have masses greater than those at the turn-off point on the main sequence and therefore must be the result of either a collision or a mass-transfer event. Because they are among the most massive and luminous objects in old clusters, they can be used as test particles with which to probe dynamical evolution. Here we report that globular clusters can be grouped into a few distinct families on the basis of the radial distribution of blue stragglers. This grouping corresponds well to an effective ranking of the dynamical stage reached by stellar systems, thereby permitting a direct measure of the cluster dynamical age purely from observed properties.

Two distinct sequences of blue straggler stars in the globular cluster M 30.

Stars in globular clusters are generally believed to have all formed at the same time, early in the Galaxy's history. 'Blue stragglers' are stars massive enough that they should have evolved into white dwarfs long ago. Two possible mechanisms have been proposed for their formation: mass transfer between binary companions and stellar mergers resulting from direct collisions between two stars. Recently the binary explanation was claimed to be dominant. Here we report that there are two distinct parallel sequences of blue stragglers in M 30. This globular cluster is thought to have undergone 'core collapse', during which both the collision rate and the mass transfer activity in binary systems would have been enhanced. We suggest that the two observed sequences are a consequence of cluster core collapse, with the bluer population arising from direct stellar collisions and the redder one arising from the evolution of close binaries that are probably still experiencing an active phase of mass transfer.

The cluster Terzan 5 as a remnant of a primordial building block of the Galactic bulge.

Globular star clusters are compact and massive stellar systems old enough to have witnessed the entire history of our Galaxy, the Milky Way. Although recent results suggest that their formation may have been more complex than previously thought, they still are the best approximation to a stellar population formed over a relatively short timescale (less than 1 Gyr) and with virtually no dispersion in the iron content. Indeed, only one cluster-like system (omega Centauri) in the Galactic halo is known to have multiple stellar populations with a significant spread in iron abundance and age. Similar findings in the Galactic bulge have been hampered by the obscuration arising from thick and varying layers of interstellar dust. Here we report that Terzan 5, a globular-cluster-like system in the Galactic bulge, has two stellar populations with different iron contents and ages. Terzan 5 could be the surviving remnant of one of the primordial building blocks that are thought to merge and form galaxy bulges.

Executive Function Index (EFI) performance in nonclinical individuals with high levels of autistic traits.

This study examined the ability of the Executive Function Index (EFI) to detect differences in executive functioning amongst participants with varying levels of subclinical autistic symptoms as quantified by the Autism Spectrum Quotient (ASQ). Participants were a nonclinical college subject sample classified as displaying either Low (0-15 ASQ score, n = 182) ASQ traits or High (16 or higher ASQ score, n = 91) ASQ traits. Participants were given the ASQ (Baron-Cohen et al., 2001) and the EFI (Spinella, 2005 ). High ASQ subjects were significantly impaired (p's < .04) on the Motivation/Drive (EFI-1) and Organization (EFI-4) subscales of the EFI, as compared to the Low ASQ subjects. However, no High/Low ASQ group differences were observed for EFI-2 (Impulse Control), EFI-3 (Empathy), EFI-5 (Planning) subscales or the EFI-Total Score (p's > .12), although these differences were in the predicted direction (High ASQ < Low ASQ). Use of the EFI as a measure of executive function performance in nonclinical ASQ trait individuals requires further study and may not be sensitive enough of an instrument to assess EF in nonclinical populations with autistic traits.

Creativity, unique designs, and schizotypy in a nonclinical sample.

The present study examined whether creativity and novel design construction differ in 60 individuals who scored low and high (based on a median split) on a measure of schizotypy. Groups differed on one measure, total designs made, but not on creativity.

Severity of bulimic symptoms is the best predictor of interference on an emotional Stroop paradigm.

OBJECTIVE: The goal of the current study was to further investigate whether an emotional Stroop effect exists among patients with bulimia nervosa. METHOD: Performances of 30 female controls, 30 females with subclinical eating disordered symptoms, and 30 females diagnosed with bulimia nervosa were compared on an emotional Stroop color naming task using stimuli separated into three areas of concern (eating, weight, and shape words). RESULTS: Results indicated that overall the three groups differed significantly on the emotional Stroop task, with the interference latency for disorder salient words progressively increasing as the severity of bulimic symptoms increased. Severity of bulimic symptoms was the best predictor of interference on the emotional Stroop paradigm. DISCUSSION: Results provide further evidence that interference on the emotional Stroop is uniquely related to the symptoms of bulimia nervosa and bear credence to the possibility of its use as an additional tool in the diagnosis of bulimia nervosa.

Paired associate learning in senile dementia of the Alzheimer type.

A study was conducted to examine the potential explicit learning ability in senile dementia of the Alzheimer type (SDAT) as a function of (1) the difficulty of the to-be-remembered material and (2) the severity of the dementia. The Associate Learning task from the Wechsler Memory Scale was administered to healthy older adults and individuals with questionable, mild, and moderate SDAT. Individuals with SDAT showed poorer learning performance across trials than healthy older adults. Individuals with questionable and mild SDAT did show evidence for learning across trials for highly related paired associates. For unrelated-paired associates, however, only individuals with questionable SDAT showed some evidence for increased learning across trials.

On the preservation of syntax in Alzheimer's disease. Evidence from written sentences.

We examined the syntactic complexity of single written sentences elicited from 368 adults undergoing examination for possible Alzheimer's disease. The clause length and composition of the sentences varied with the severity of dementia. The nondemented adults' sentences contained more propositions, main and secondary verbs, and conjunctions than those produced by the mildly and moderately demented adults. Sentence length in clauses, propositional content, and the use of conjunctions and main and secondary verbs discriminated among stages of the severity of the disease. The present results suggest that, while dementia severity affects written linguistic output, such output is, nonetheless, grammatic and coherent.

Individual differences in information-processing rate and amount: implications for group differences in response latency.

Research on group differences in response latency often has as its goal the detection of Group x Treatment interactions. However, accumulating evidence suggests that response latencies for different groups are often linearly related, leading to an increased likelihood of finding spurious overadditive interactions in which the slower group produces a larger treatment effect. The authors propose a rate-amount model that predicts linear relationships between individuals and that includes global processing parameters based on large-scale group differences in information processing. These global processing parameters may be used to linearly transform response latencies from different individuals to a common information-processing scale so that small-scale group differences in information processing may be isolated. The authors recommend linear regression and z-score transformations that may be used to augment traditional analyses of raw response latencies.

Lexical ambiguity and the timecourse of attentional allocation in word recognition.

In two experiments the allocation of attention during the recognition of ambiguous and unambiguous words was investigated. In Experiment 1, separate groups performed either lexical decision, auditory probe detection, or their combination. In the combined condition probes occurred 90, 180, or 270 ms following the onset of the lexical-decision target. Lexical decisions and probe responses were fastest for ambiguous words, followed by unambiguous words and pseudowords, respectively, which indicated that processing ambiguous words was less attention demanding than unambiguous words or pseudowords. Attention demands decreased across the timecourse of word recognition for all stimulus types. In Experiment 2, one group performed the lexical-decision task alone, whereas another group performed the lexical-decision task during the retention interval of a short-term memory task. The results were consistent with those from Experiment 1 and showed that word recognition is an attention-demanding process and that the demands are inversely related to the number of meanings of the stimulus. These results are discussed with regard to the structure of the mental lexicon (i.e., single vs. multiple lexical entries) and the effect of such a structure on attentional mechanisms.

An analysis of the "eveningness-morningness" dimension in "depressive" college students.

BACKGROUND: Circadian variability in depression has not been well characterized with respect to the "eveningness-morningness" dimension. METHODS: The "eveningness-morningness" dimension, as measured by the Home and Ostberg questionnaire, was examined among a student population (n = 1617) that was named as "depressive". Three depression scales (BDI, GDS-SF, and CESD) were used to determine "depressiveness". The Horne and Ostberg questionnaire was used to measure the degree of "eveningness-morningness". It was hypothesized that there would be negative and significant correlations between the scores on the Horne and Ostberg questionnaire and the depression scales. Consequently, it was expected that there would be a significantly higher number of evening types than the morning types among the participants identified as "depressives". RESULTS: There were significant, negative correlations between the Horne and Ostberg questionnaire scores and the responses on the 3 depression scales (for BDI r= -.174, GDS-SF r= -.182, CESD r = -.176, all p < .001). Also, a significantly higher incidence of evening types than of the morning types among the "depressive" students was found (chi2 = 11.18, p < .01). LIMITATIONS: It is uncertain to what extent these data generalize to clinical populations. CONCLUSIONS: "Depressive" college students are more likely to be evening types.

General slowing in semantic priming and word recognition.

Analyses of lexical decision studies revealed that (a) older (O) adults' mean semantic priming effect was 1.44 times that of younger (Y) adults, (b) regression lines describing the relations between older and younger adults' latencies in related (O = 1.54 Y-112 and unrelated conditions (O = 1.50 Y-93) were not significantly different, and (c) that there was a proportional relation between older and younger adults' priming effects (O = 1.48 Y-2). Analyses of word-naming studies yielded similar results. Analyses of delayed pronunciation data (Balota & Duchek, 1988) revealed that word recognition was 1.47 times slower in older adults, whereas older adults' output processes were only 1.26 times slower. Overall, analyses of whole latencies and durations of component processes provide converging evidence for a general slowing factor of approximately 1.5 for lexical information processing.

Influence of emotional state on irrelevant thoughts.

The fan effect paradigm was used to investigate the influence of emotional mood state on longterm memory retrieval (Anderson, 1983). Subjects learned target facts embedded in unrelated sentences to a specified criterion and were then given a happy, sad, or neutral mood induction. Mean response times (RTs) and error rates were analyzed in a speeded recognition test in which subjects distinguished between the learned facts and foil facts (foil facts were constructed by recombining the same concepts). A follow-up lexical decision task indicated that mean RT was positively correlated with an increase in the weighted proportion of irrelevant thoughts produced by subjects in an induced sad mood. Results suggest that irrelevant thoughts associated with the sad mood state interfered with more relevant, task-oriented, thoughts and support the notion that sad mood is related to a failure to inhibit irrelevant information.

The relationship between cognitive ability and positive and negative priming in identity and spatial priming tasks.

The authors examined whether stimulus activation and inhibition in the identity priming task are related to the temporal lobe, and whether these processes in the spatial priming task are related to the parietal lobe. Forty participants performed spatial and identity positive and negative priming tasks, the Vandenberg Mental Rotation task, and the Digit Span task. Both men and women showed significant positive and negative priming in the identity and spatial tasks with no gender difference. The magnitude of identity positive priming was predicted by the Digit Span task, and the magnitude of spatial positive priming was predicted by the mental rotation task. Only women showed a correlation between spatial ability and spatial negative priming. The results are partially consistent with the dorsal-ventral model of cognitive inhibition.

Do individuals at risk for eating disorders exhibit negative priming deficits?

Fifty people (25 at risk for an eating disorder, 25 controls) performed a simple reaction-time (SRT) task and a negative-priming (NP) task. The two groups did not differ on the SRT task. For the NP task, the controls displayed the NP effect (responses on critical trials were slower than responses on control trials). At-risk participants, however, revealed no such NP effect. Although the pattern of NP performance in the at-risk participants may indicate that they as a group had deficiencies in their ability to inhibit irrelevant information, it is also possible that issues related to obsessionality, perfectionism, and restraint in the at-risk group affected the results.

Institutional Review Board issues related to special populations.

The present article begins with an introduction to the role of Institutional Review Boards (IRBs) in research activities in general and proceeds to issues IRBs face with relation to special populations, including children and terminally ill individuals, as well as developmentally disabled and cognitively impaired persons. A historical overview of research with these special populations is included, and the report concludes with a real-world example of how IRB-related issues with developmentally disabled and cognitively impaired individuals are discussed and resolved.

Age and the allocation of attention across the time course of word recognition.

Younger and older adults performed lexical decisions on ambiguous words, unambiguous words, and pseudowords, and simultaneously responded to an auditory probe presented at stimulus onset asynchronies (SOAs) of 90, 180, or 270 ms. For both age groups, lexical decisions and probe responses were faster for ambiguous words than for unambiguous words, and slowest for pseudowords. For the older adults, but not the younger adults, lexical decisions were slower when the probe was presented (the dual-task condition), compared with a control condition in which the lexical decision was performed alone. The older participants also showed slower tone-detection responses in the dual-task condition than when the tone was presented alone. For all participants, proportional tone-detection times (compared with tones in isolation) decreased with increasing SOA, but this decrease was less pronounced in the older group. Finally, the time between responses in the dual-task condition was longer for older than for younger adults. The results indicate that word meaning influences the allocation of attention similarly for younger and older adults, but that older adults suffer a cost and become disproportionately slower in processes related to response coordination and output.

The role of vocabulary ability during visual word recognition in younger and older adults.

The role that vocabulary ability plays in adult age differences in word recognition was investigated. In Experiment 1, 44 older adults (ages 61-93 years) were compared with 44 younger adults (ages 18-39 years) on a standard lexical-decision task, with ambiguous words, unambiguous words, and pseudowords serving as stimuli. In Experiment 1, the Wechsler Adult Intelligence Scale-Revised (WAIS-R; D. Wechsler, 1981) vocabulary performance was uncontrolled across the younger and older adults, and the older adults had higher WAIS-R scores. There was no Group x Stimulus interaction. In Experiment 2, the data from the same 44 older adults were compared with data from a new sample of 44 younger adults (ages 18-44). Both groups were then matched on WAIS-R performance. Results revealed a significant Group x Stimulus interaction. Reaction time differences between the younger and older groups on the ambiguous words and unambiguous words were identical. The differences in reaction times for words and pseudowords were greater in the older adults. The importance of vocabulary ability during word recognition and lexical processing is discussed.

Large-scale demonstration experiment of mental imagery ability.

The present article describes a demonstration experiment used in a large introductory psychology class pertaining to mental imagery ability. The experiment is effective in providing a concrete instance of mental imagery as well as an effective discussion regarding individual differences and gender differences in imagery ability.

Psychology of computer use: XV. Effects of display format on reading text from a CRT.

Comprehension of brief computer-displayed text was investigated. Question-answering ability was affected by both rate of text presentation and text difficulty. More importantly, though, text presented one word at a time was comprehended better than text presented in multiword units or chunks. Results are discussed with regard to optimizing reading from computer displays.