Effects of sleep deprivation on Color-Word, Emotional, and Specific Stroop interference and on self-reported anxiety

The aim of this study was principally to assess the impact of sleep deprivation on interference performance in short Stroop tasks (Color-Word, Emotional, and Specific) and on subjective anxiety. Subjective sleepiness and performance on a psychomotor sustained attention task were also investigated to validate our protocol of sleep deprivation. Twelve healthy young subjects were tested at four-hourly intervals through a 36-h period of wakefulness under a constant routine protocol. Analyses of variance for repeated measurements revealed that self-assessment of sleepiness on a visual analogue scale as well as mean reaction time performance on the sustained attention task, both for the first minute and for 10 min of testing, were worsened by sleep deprivation. Analyses revealed an increase in self-reported anxiety scores on the STAI questionnaire but did not reveal any significant effect after sleep deprivation either on indexes of interference or on accuracy in Stroop tasks. However, analyses showed sensitivity to circadian effect on verbal reaction times in the threat-related (Emotional) and sleep-related (Specific) Stroop tasks. We concluded that 36 h of prolonged wakefulness affect self-reported anxiety and Emotional Stroop task resulting in a cognitive slowing. Moreover, total sleep deprivation does not affect interference control in any of the three short Stroop tasks.     

The discrimination of temporal fine structure in call-like harmonic sounds by birds

Thresholds for discriminating changes in the temporal fine structure of call-like, harmonic sounds were measured in zebra finches (Taeniopygia guttata) and budgerigars (Melopsittacus undulatus). Birds could detect changes in periods as short as 1.225 ms at near 100% accuracy even when spectral and envelope cues were identical, as in time-reversed stimuli. Humans performed poorly on such stimuli, paralleling results from previous studies. Bird thresholds were in the range of those reported in neurophysiological studies of the songbird high vocal center (HVC) to temporally modified conspecific songs. Taken together, these results show that birds can hear differences in temporal fine structure in their natural vocalizations that go beyond human capabilities, but whether these abilities have communicative relevance remains to be seen.     

Decision making and interference in the domestic cat (Felis catus)

Domestic cats (Felis catus) received a task in which an obstacle was introduced at the time they were ready to reach for 1 among 2 or 3 baited targets. The results revealed that when the initially chosen direction (i.e., before the introduction of the obstacle) and the new one were orthogonal, the cats reassessed distance, angular deviation, and visibility once they had turned around the obstacle (Experiments 1, 2, and 3). Then the cats chose a different target than the one that would have been chosen had there been no obstacle. When both the initially chosen and the new direction matched (Experiment 4), the cats kept intact their initial decision. The discussion focuses on the nature of the representational system of the cat. The discussion also emphasizes comparisons with dogs (i.e., cooperative hunters).     

Phenomenal characteristics of autobiographical memories for social and non-social events in social phobia

Previous studies failed to show clear differences between people with social phobia and non-anxious individuals regarding the specificity and affective intensity of their autobiographical memories for social events. However, these studies did not assess the subjective experience associated with remembering. In this study, people with social phobia and non-anxious control participants recalled social and non-social events, and rated the phenomenal characteristics of their memories. The memories of people with social phobia for social events contained fewer sensorial details but more self-referential information than controls' memories. In addition, people with social phobia remembered social situations from an observer perspective, viewing themselves as if from outside, to a greater extent than controls. By contrast, the two groups did not differ concerning their memories for non-social events. These findings are discussed in relation to cognitive models of social phobia.     

First- and third-person approaches in implicit learning research

How do we find out whether someone is conscious of some information or not? A simple answer is “We just ask them”! However, things are not so simple. Here, we review recent developments in the use of subjective and objective methods in implicit learning research and discuss the highly complex methodological problems that their use raises in the domain.     

Instrumental learning in hyperdopaminergic mice

In two experiments we investigated the effects of elevated dopaminergic tone on instrumental learning and performance using dopamine transporter knockdown (DAT KD) mice. In Experiment 1, we showed that both DAT KD mice and wild-type controls were similarly sensitive to outcome devaluation induced by sensory specific satiety, indicating normal action-outcome learning in both groups. In Experiment 2, we used a Pavlovian-to-instrumental transfer procedure to assess the potentiation of instrumental responding by Pavlovian conditional stimuli (CS). Although during the Pavlovian training phase the DAT KD mice entered the food magazine more frequently in the absence of the CS, when tested later both groups showed outcome-selective PIT. These results suggest that the elevated dopaminergic tone reduced the selectivity of stimulus control over conditioned behavior, but did not affect instrumental learning.     

Does the mastery of center-embedded linguistic structures distinguish humans from nonhuman primates?

In a recentScience article, Fitch and Hauser (2004; hereafter, F&H) claimed to have demonstrated that cotton-top tamarins fail to learn an artificial language produced by a phrase structure grammar (Chomsky, 1957) generating center-embedded sentences, whereas adult humans easily learn such a language. We report an experiment replicating the results of F&H in humans but also showing that subjects learned the language without exploiting in any way the center-embedded structure. When the procedure was modified to make the processing of this structure mandatory, the subjects no longer showed evidence of learning. We propose a simple interpretation for the difference in performance observed in F&H’s task between humans and tamarins and argue that, beyond the specific drawbacks inherent in F&H’s study, researching the source of the inability of nonhuman primates to master language within a framework built around Chomsky’s hierarchy of grammars is a conceptual dead end.     

Heart rate changes during conditioning-specific reflex modification of the rabbit's (Oryctolagus cuniculus) nictitating membrane response

Conditioning-specific reflex modification (CRM) of the rabbit's nictitating membrane response (NMR) involves changes in responding to an unconditioned stimulus (US) when the US is tested in the absence of the conditioned stimulus. Previous experiments have shown that CRM is a function of the type and intensity of the aversive US used during classical conditioning. As a result, it has been suggested that CRM may be mediated, at least in part, by the aversiveness of the US. Here, we show that by using a moderately intense electrical pulse to the skin as a US, CRM of the rabbit NMR is accompanied by an increase in heart rate. The largest changes in heart rate occur at US intensities that produce the strongest levels of CRM. The heart rate data show that there may be an increased emotional/arousal component to the US that is correlated with CRM and support the use of CRM as a potential model for posttraumatic stress disorder.     

Very young children are insensitive to picture- but not object-orientation

In two experiments on very young children's response to the orientation of pictures and objects, 18-, 24- and 30-month-old children showed no preference for upright pictures over inverted ones. More importantly, we found that children in all three age groups were equally accurate and equally fast at identifying depicted objects regardless of orientation. These studies further established that young children's insensitivity to picture orientation does not extend to objects. These results, in combination with the earlier ones, indicate that only gradually do young children come to share the picture orientation preference of adults and older children and that their adoption of the orientation convention is not based on changes in their ability to process upright and inverted images.     

Intuitive decision making in complex situations: Somatic markers in an artificial grammar learning task

In this article, we explore the extent to which implicit learning is subtended by somatic markers, as evidenced by skin conductance measures. On each trial, subjects were asked to decide which “word” from a pair of “words” was the “correct” one. Unknown to the subjects, each “word” of a pair was constructed using a different set of rules (Grammar Aand Grammar B). A (monetary) reward was given if the subject chose the “word” from Grammar A. Choosing the Grammar B word resulted in (monetary) punishment. Skin conductance was measured during each of 100 trials. After each set of 10 trials, the subjects were asked how they selected the “correct word.” Task performance increased long before the subjects could even formulate a single relevant rule. In this preconceptual phase of the experiment, skin conductance was larger before incorrect than before correct choices. Thus, it was shown that artificial grammar learning is accompanied by a somatic marker, possibly “warning” the subject of the incorrect decision.