The temporal selectivity of additive factor effects on the reaction process revealed in ERP component latencies

An experiment was conducted to relate individual components of the event-related brain potential to specific stages of information processing in a two-choice reaction time (RT) task in a group of undergraduate students. Specifically, the latency of the P300 component and the lateralized readiness potential (LRP) were studied as a function of variations in stimulus degradation and response complexity. It was hypothesized that degrading the stimulus would delay the P300 and LRP to the same extent as RT, and that increasing response complexity would affect RT but not P300 latency. The extant literature did not permit any hypothesis regarding the effect of response complexity on LRP latency. The two task variables were found to have additive effects on RT. As predicted, variations in stimulus degradation influenced the latencies of both components, whereas alterations in response complexity had no effect on P300 latency. A significant new finding was that the onset latency of the LRP remained unchanged across levels of response complexity. The overall pattern of results supports the notion of temporal selectivity of stage manipulations that is derived from discrete stage models of human information processing. Furthermore, these results refine the functional interpretation of the LRP by indicating that within the conceptual framework of a stage model the processes this component indexes succeed the start of response choice but precede the start of motor programming.     

Effects of mixed versus blocked design on stimulus evaluation: combining underadditive effects

According to the asynchronous discrete coding model of Miller, two manipulations should display underadditive effects on reaction time if they slow down noncontingent stages associated with the processing of two separable dimensions of a stimulus. Underadditive effects are also predicted by a dual route model when a task variable is factorially varied with design type (mixed vs blocked). Interpretations of both underadditive effects and their combination were evaluated. Intact and degraded stimuli were presented to 18 young adults either in a single block (mixed) or in separate blocks (blocked). Spatial stimulus-response (S-R) compatibility was manipulated in all conditions. Stimulus degradation and S-R compatibility interacted underadditively, but only in blocked presentations. Both interpretations of underadditive effects were supported. Eye-movement registrations provided additional support for the alternative routes model.     

What–Where–When memory in magpies (Pica pica)

Some animals have been shown to be able to remember which type of food they hoarded or encountered in which location and how long ago (what–where–when memory). In this study, we test whether magpies (Pica pica) also show evidence of remembering these different aspects of a past episode. Magpies hid red- and blue-dyed pellets of scrambled eggs in a large tray containing wood shavings. They were allowed to make as many caches as they wanted. The birds were then returned either the same day or the next day to retrieve the pellets. If they returned the same day, one colour of pellets was replaced with wooden beads of similar size and colour, while if they returned the next day this would happen to the other colour. Over just a few trials, the birds learned to only search for the food pellets, and ignore the beads, of the appropriate colour for the given retention interval. A probe trial in which all items were removed showed that the birds persisted in searching for the pellets and not the beads. This shows that magpies can remember which food item they hoarded where, and when, even if the food items only differ from each other in their colour and are dispersed throughout a continuous caching substrate.     

Clamped Corticosterone (B) Reveals the Effect of Endogenous B on Both Facilitated Responsivity to Acute Restraint and Metabolic Responses to Chronic Stress

To determine the effects of both corticosterone (B) and chronic stressors on acute ACTH responses to restraint, young male rats were exposed to streptozotocin-induced diabetes, cold (5-7 degreesC) or intracerebroventricular (icv) neuropeptide Y (NPY) for 5 d and then exposed to restraint within 2 h after lights on. Two groups of rats were studied: intact and adrenalectomized replaced with B pellets that maintained plasma B in the normal mean 24-h range of intact rats. In addition to ACTH and B responses to restraint on d 5, body weight, food intake, fat depots, glucose and other hormones were measured to determine the role of stress-induced elevations in B on energy balance. ACTH responses to restraint were normal in intact rats subjected to diabetes or cold. By contrast, there was no ACTH or B response to restraint in NPY-infused intact rats. All 3 groups of chronically stimulated adrenalectomized rats with clamped B had facilitated ACTH responses to restraint compared to their treatment controls. Overall food intake increased in all groups of stressed rats; however, augmented intake occurred only during the light in intact rats and equally in the light and dark in B-clamped rats. White adipose depot weights were decreased by both diabetes and cold and increased by NPY in intact rats; the decreases with cold and increases with NPY were both blunted and changes in fat stores were not significant in adrenalectomized, B-clamped rats. We conclude that: 1. diabetes- and cold-induced facilitation of restraint-induced afferent input to hypothalamic control of the hypothalamo-pituitary-adrenal (HPA) axis is opposed in intact rats by the elevated feedback signal of B secretion; 2. NPY does not induce facilitation of afferent stress pathways; 3. chronic stimulation of the HPA axis induces acute hyperresponsiveness of hypothalamic neurons to restraint provided that the afferent input of this acute stimulus is not prevented by B feedback; 4. stimulus-induced elevations in B secretion result in day-time feeding; 5. insensitivity of both caloric efficiency and white fat stores to chronic stress in adrenalectomized, B-clamped rats results from loss of normally variable B levels.     

Implicit and explicit alcohol-related cognitions in heavy and light drinkers

Implicit and explicit alcohol-related cognitions were measured in 2 dimensions: positive-negative (valence) and arousal-sedation, with 2 versions of the Implicit Association Test (IAT; A. G. Greenwald, D. E. McGhee, & J. L. Schwartz) and related explicit measures. Heavy drinkers (n = 24) strongly associated alcohol with arousal on the arousal IAT (especially men) and scored higher on explicit arousal expectancies than light drinkers (n = 24). On the valence IAT, both light and heavy drinkers showed strong negative implicit associations with alcohol that contrasted with their positive explicit judgments (heavy drinkers were more positive). Implicit and explicit cognitions uniquely contributed to the prediction of 1-month prospective drinking. Heavy drinkers' implicit arousal associations could reflect the sensitized psychomotor-activating response to drug cues, a motivational mechanism hypothesized to underlie the etiology of addictive behaviors.     

Familial correlates of social anxiety in children and adolescents

Retrospective studies suggest a relationship between parental rearing practices and social phobia. The present study investigated whether socially anxious children perceive their current parental rearing as rejecting, overprotective, and lacking emotional warmth, and as emphasizing the importance of other's opinion, and de-emphasizing social initiatives and family sociability. Furthermore, we examined whether parents of socially anxious children report to rely on such rearing practices, and suffer themselves from social fears. A regression analysis as well as extreme group comparisons were applied. Little support was found for the presumed role of the assessed family rearing aspects in the development of social anxiety in children. Solely family sociability (children's and mothers' report) and children's perception of overprotection of the mother predicted social anxiety in the regression analysis. Given the influence of the mentioned rearing practices, social anxiety of the mother still significantly predicted social anxiety of the child. In the extreme group comparisons, differences in the expected direction were found between socially anxious and normal children on parental rejection, emotional warmth, and family sociability. However, the lack of differences between socially anxious and clinical control children suggests that these variables do not form a specific pathway to social fears.     

Workplace violence and the changing nature of work in Europe: Trends and risk groups

Incidence rates of third party workplace violence in Europe have increased, but little is known about the causes thereof. It has been suggested that the growth of the service sector and the intensification of work could be responsible for the increase. This study aimed to identify trends in the prevalence of physical workplace violence across Europe, as well as to uncover factors explaining these trends. Three cross-sectional waves (1995, 2000, and 2005) of the European Working Conditions Survey were used, involving 58,520 workers and covering 15 European member states. Logistic regression analyses were performed to investigate associations between work characteristics and violence prevalence. Workplace violence increased significantly during the study interval. Although violence was clearly related to specific characteristics of the labour market (gender, age, sector, etc.) and the work environment (client contact frequency, time pressure, control, and computer work), recent changes in the European labour market composition and work environment could not explain the increase in violence. In jobs characterized by high levels of computer work in particular, violence appears to be an emerging risk. Our results suggest that the nature (and perhaps quality) of client contact is changing, leading to higher violence risks.     

Biased processing of emotional information in sub-clinical anxiety: Evidence from Simon effects

We tested the idea that in high trait-anxiety, behavioural responses are influenced by spatial correspondence to emotional information. It is suggested that if an emotional stimulus is preferentially processed, it may act as if presented alone and yield a Simon effect: faster responses when stimulus and response spatially correspond than when not. High-trait-anxious undergraduates indeed showed a content-specific Simon effect for social-threat (not physical-threat) words that were presented together with a neutral word for 14 ms; they showed the reverse response pattern for positive words. Low-anxious undergraduates had no bias. When presentation time was lengthened to 500 ms, the response pattern for social-threat and positive words shown by high-anxious undergraduates reversed as compared to the pattern with 14 ms, but there were no significant group differences. These results can be taken to suggest that in high trait-anxiety, the processing of social-threat is specifically prioritized; social-threat and positive information may elicit an immediate response, counteracted by mood-regulation strategies. We argue that the present approach opens up interesting avenues for investigating biased information processing and response tendencies.     

Do humans use episodic memory to solve a <Emphasis Type="Italic">What</Emphasis>-<Emphasis Type="Italic">Where</Emphasis>-<Emphasis Type="Italic">When</Emphasis> memory task?

What-Where-When (WWW) memory tasks have been used to study episodic(-like) memory in non-human animals. In this study, we investigate whether humans use episodic memory to solve such a WWW memory task. Participants are assigned to one of two treatments, in which they hide different coin types (what) in different locations (where) on two separate occasions (when). In the Active treatment, which mimics the animal situation as closely as possible, participants are instructed to memorize the WWW information; in the Passive treatment, participants are unaware of the fact that memory will be tested. In both groups, the majority of participants report using a mental time travel strategy to solve the task, and performance on a different episodic memory test significantly predicts performance on the WWW memory task. This suggests that the WWW memory task is a good test of episodic memory in humans. Participants remember locations and coins from the first hiding session better than they do those of the second hiding session, suggesting their memories may be reinforced during the second hiding session. We also investigated how well episodic memory performance predicted performance on the three aspects of the WWW memory task separately. In the Passive treatment, episodic memory performance predicts performance on all three aspects of the WWW memory task equally. However, in the Active treatment it only predicts performance on the what component. This could imply that during active encoding a different memory system is used for where and when information than during passive encoding. Encoding of what information seems to rely on episodic memory processing in both conditions.     

Magpies can use local cues to retrieve their food caches

Much importance has been placed on the use of spatial cues by food-hoarding birds in the retrieval of their caches. In this study, we investigate whether food-hoarding birds can be trained to use local cues (“beacons”) in their cache retrieval. We test magpies (Pica pica) in an active hoarding-retrieval paradigm, where local cues are always reliable, while spatial cues are not. Our results show that the birds use the local cues to retrieve their caches, even when occasionally contradicting spatial information is available. The design of our study does not allow us to test rigorously whether the birds prefer using local over spatial cues, nor to investigate the process through which they learn to use local cues. We furthermore provide evidence that magpies develop landmark preferences, which improve their retrieval accuracy. Our findings support the hypothesis that birds are flexible in their use of memory information, using a combination of the most reliable or salient information to retrieve their caches.