Interference resolution in major depression

In two experiments, we investigated individual differences in the ability to resolve interference in participants diagnosed with major depressive disorder (MDD). Participants were administered the “Ignore/Suppress” task, a short-term memory task composed of two steps. In Step 1 (“ignore”), participants were instructed to memorize a set of stimuli while ignoring simultaneously presented irrelevant material. In Step 2 (“suppress”), participants were instructed to forget a subset of the previously memorized material. The ability to resolve interference was indexed by response latencies on two recognition tasks in which participants decided whether a probe was a member of the target set. In Step 1, we compared response latencies to probes from the to-be-ignored list with response latencies to nonrecently presented items. In Step 2, we compared response latencies to probes from the to-be-suppressed list with response latencies to nonrecently presented items. The results indicate that, compared with control participants, depressed participants exhibited increased interference in the “suppress” but not in the “ignore” step of the task, when the stimuli were negative words. No group differences were obtained when we presented letters instead of emotional words. These findings indicate that depression is associated with difficulty in removing irrelevant negative material from short-term memory.     

Developmental changes in automatic rule‐learning mechanisms across early childhood

Infants’ ability to learn complex linguistic regularities from early on has been revealed by electrophysiological studies indicating that 3‐month‐olds, but not adults, can automatically detect non‐adjacent dependencies between syllables. While different ERP responses in adults and infants suggest that both linguistic rule learning and its link to basic auditory processing undergo developmental changes, systematic investigations of the developmental trajectories are scarce. In the present study, we assessed 2‐ and 4‐year‐olds’ ERP indicators of pitch discrimination and linguistic rule learning in a syllable‐based oddball design. To test for the relation between auditory discrimination and rule learning, ERP responses to pitch changes were used as predictor for potential linguistic rule‐learning effects. Results revealed that 2‐year‐olds, but not 4‐year‐olds, showed ERP markers of rule learning. Although, 2‐year‐olds’ rule learning was not dependent on differences in pitch perception, 4‐year‐old children demonstrated a dependency, such that those children who showed more pronounced responses to pitch changes still showed an effect of rule learning. These results narrow down the developmental decline of the ability for automatic linguistic rule learning to the age between 2 and 4 years, and, moreover, point towards a strong modification of this change by auditory processes. At an age when the ability of automatic linguistic rule learning phases out, rule learning can still be observed in children with enhanced auditory responses. The observed interrelations are plausible causes for age‐of‐acquisition effects and inter‐individual differences in language learning.     

Updating the contents of working memory in depression: interference from irrelevant negative material

This study was designed to assess the effects of irrelevant emotional material on the ability to update the contents of working memory in depression. For each trial, participants were required to memorize 2 lists of emotional words and subsequently to ignore 1 of the lists. The impact of irrelevant emotional material on the ability to update the contents of working memory was indexed by response latencies on a recognition task in which the participants decided whether or not a probe was a member of the relevant list. The authors compared response latencies to probes from the irrelevant list to response latencies to novel probes of the same valence (intrusion effect). The results indicate that, compared to control participants in both neutral and sad mood states, depressed participants showed greater intrusion effects when presented with negative words. In an important finding, intrusion effects for negative words were correlated with self-reported rumination. These findings indicate that depression is associated with difficulties removing irrelevant negative material from working memory. Results also indicate that the increased interference from irrelevant negative material is associated with rumination.     

The number of active palmar sweat glands (palmar sweat index,PSI) as an activation measure in field studies

The number of active sweat glands within a defined area of a fingertip, called the palmar sweat index (PSI), can be easily determined by means of the plastic fingerprint method. Two experiments were carried out to demonstrate the applicability of this technique in field research and to investigate the properties of the PSI as an activation parameter. In Experiment 1 (in a blood donors’ ward), PSI rose significantly during venous puncture and dropped after the cannula had been installed. In Experiment 2 (in a dental office), PSI values increased when patients were seated in the dental chair and rose to a higher level at the dentist’s entry. Values after treatment were significantly lower. In both experiments, it was observed that the initial assessments yielded higher PSI values. This is best explained as a reaction to the assessment procedure itself, and it is recommended that the first two prints not be used for the determination of baseline values.     

Coincidence of attention deficit disorder and atopic disorders in children: Empirical findings and hypothetical background

ADDH children are often reported to display signs of allergies to various substances and/or atopic (AT) symptoms (i.e., atopic eczema, hay fever, or asthma). Since, at least for a subgroup of these children, a common biological background for both ADD and atopy may be assumed that may involve brain catecholamines, our hypothesis was that in a group of AT children (mainly atopic eczema) signs of ADD should appear more often than in controls. Parental hyperactivity ratings revealed a significantly higher frequency of ADD symptoms in the AT group, and laboratory tests sensitive to attentional capacity and inhibitory functions showed poorer performance in the AT children, the findings being similar to those reported in hyperactives. Thus, our results add support to the assumption of a common predisposing factor for both AT and ADDH in a subgroup of children.     

Gravitational lensing and Hacking's extragalactic irreality

In Extragalactic Reality: The Case of Gravitational Lensing Hacking resumes the discussion of scientific realism from the last chapter of Representing and Intervening. Since the criterion of manipulability cannot be applied to astronomical objects, experimental entity realism seems to be restricted to terrestrial entities. In fact, Hacking explicitly argues against astronomical realism. The case at issue is the existence of gravitational lenses. In this paper, I question Hacking's chief witness for astronomical antirealism: the gravitational lens system “0957+ 561”. It will be shown that Hacking's argumentation is misleading. Discussing astronomical realism as theory realism, Hacking focuses on the question of how to infer the existence of gravitational lenses from the truth of gravitational lens theory. But neither the reconstruction of gravitational lensing in terms of inference to the best explanation (IBE) nor the argument of underdetermination are tenable under closer inspection. My thesis is that a realist account of gravitational lensing can be given by relying on observation, causal capacities and home truths.     

Methylphenidate slows reactions of children with attention deficit disorder during and after an error

A Sternberg memory search task was administered under placebo and methylphenidate to 42 children with cross-situational attention deficit disorder (ADD), 31 children with cross-situational ADD plus oppositional features, and 25 patients with marginal ADD. Overall, stimulant medication enhanced accuracy and speed. In addition, patients reacted faster on correct responses not preceded by an error than on errors (especially false alarms) or on correct responses following an error. The slowness during error reactions may reflect decreased confidence or confusion during stimulus classification. This uncertainty may also lead subjects to respond with greater caution, hence more slowly, on correct responses following errors. Notably, methylphenidate increased the slowing of reactions on error trials as well as on correct reactions following an error. Stimulant medication may augment subjects' persistence when they are uncertain or confused, thereby heightening caution and promoting accuracy on succeeding trials. Consistent with previous reports of the generality of enhancement of performance by stimulant medication, the impact of methylphenidate was comparable for the three subtypes of ADD studied.Jaine Strauss is at Macalester College.This research was supported by National Institute of Mental Health Grants MH32103 and MH38118. We thank Rachel Avery, Christine Carriuolo, Lawrence Ota, the late Helen Pollock, and the University of Rochester's Strong Memorial Hospital Pharmacy for their assistance.     

Testing problem-solving capacities: differences between individual testing and social group setting

Testing animals individually in problem-solving tasks limits distractions of the subjects during the test, so that they can fully concentrate on the problem. However, such individual performance may not indicate the problem-solving capacity that is commonly employed in the wild when individuals are faced with a novel problem in their social groups, where the presence of a conspecific influences an individual’s behaviour. To assess the validity of data gathered from parrots when tested individually, we compared the performance on patterned-string tasks among parrots tested singly and parrots tested in social context. We tested two captive groups of orange-winged amazons (Amazona amazonica) with several patterned-string tasks. Despite the differences in the testing environment (singly vs. social context), parrots from both groups performed similarly. However, we found that the willingness to participate in the tasks was significantly higher for the individuals tested in social context. The study provides further evidence for the crucial influence of social context on individual’s response to a challenging situation such as a problem-solving test.