Esther van den Bos

Sense of body and sense of action both contribute to self-recognition

Recognizing oneself, easy as it appears to be, seems at least to require awareness of ones body and ones actions. To investigate the contribution of these factors to self-recognition, we presented normal subjects with an image of both their own and the experimenters hand. The hands could make the same, a different or no movement and could be displayed in various orientations. Subjects had to tell whether the indicated hand was theirs or not. The results showed that a congruence between visual signals and signals indicating the position of the body is one component on which self-recognition is based. Recognition of ones actions is another component. Subjects had most difficulty in recognizing their hand when movements were absent. When the two hands made different movements, subjects relied exclusively on the movement cue and recognition was almost perfect. Our findings are in line with pathological alterations in the sense of body and the sense of action.

Effects of grammar complexity on artificial grammar learning.

The present study identified two aspects of complexity that have been manipulated in the implicit learning literature and investigated how they affect implicit and explicit learning of artificial grammars. Ten finite state grammars were used to vary complexity. The results indicated that dependency length is more relevant to the complexity of a structure than is the number of associations that have to be learned. Although implicit learning led to better performance on a grammaticality judgment test than did explicit learning, it was negatively affected by increasing complexity: Performance decreased as there was an increase in the number of previous letters that had to be taken into account to determine whether or not the next letter was a grammatical continuation. In particular, the results suggested that implicit learning of higher order dependencies is hampered by the presence of longer dependencies. Knowledge of first-order dependencies was acquired regardless of complexity and learning mode.

Structural selection in implicit learning of artificial grammars

In the contextual cueing paradigm, Endo and Takeda (in Percept Psychophys 66:293–302, 2004) provided evidence that implicit learning involves selection of the aspect of a structure that is most useful to one’s task. The present study attempted to replicate this finding in artificial grammar learning to investigate whether or not implicit learning commonly involves such a selection. Participants in Experiment 1 were presented with an induction task that could be facilitated by several characteristics of the exemplars. For some participants, those characteristics included a perfectly predictive feature. The results suggested that the aspect of the structure that was most useful to the induction task was selected and learned implicitly. Experiment 2 provided evidence that, although salience affected participants’ awareness of the perfectly predictive feature, selection for implicit learning was mainly based on usefulness.

Intentional artificial grammar learning: When does it work?

Actively searching for the rules of an artificial grammar has often been shown to produce no more knowledge than memorising exemplars without knowing that they have been generated by a grammar. The present study investigated whether this ineffectiveness of intentional learning could be overcome by removing dual task demands and providing participants with more specific instructions. The results only showed a positive effect of learning intentionally for participants specifically instructed to find out which letters are allowed to follow each other. These participants were also unaffected by a salient feature. In contrast, for participants who did not know what kind of structure to expect, intentional learning was not more effective than incidental learning and knowledge acquisition was guided by salience.

Two-year stability of individual differences in (para)sympathetic and HPA-axis responses to public speaking in childhood and adolescence.

Long-term stability of individual differences in stress responses has repeatedly been demonstrated in adults, but few studies have investigated the development of stability in adolescence. The present study was the first to investigate the stability of individual differences in heart rate, parasympathetic (RMSSD, pNN50, HF), sympathetic (LF/HF, SC), and HPA-axis (salivary cortisol) responses in a youth sample (8-19 years). Responses to public speaking were measured twice over 2 years. Stability was moderate for absolute responses and task delta responses of HR, RMSSD, pNN50, and HF. Stability was lower for SC and task delta responses of LF/HF and cortisol. Anticipation delta responses showed low stability for HR and cortisol. The latter was moderated by age or puberty, so that individual differences were more stable in more mature individuals. The results support the suggestion that stress responses may be reset during adolescence, but only for the HPA axis.

Social anxiety and the cortisol response to social evaluation in children and adolescents

Contradictory findings have been reported on the relation between social anxiety and the cortisol response to social evaluation in youth. The present longitudinal study aimed to clarify this relation by taking pubertal development into account. Data were collected in two waves, two years apart, for a community sample of 196 participants, aged 8-17 years at Time 1. Pubertal development and social anxiety were assessed with self-report questionnaires. Salivary cortisol was obtained before and after participants completed the Leiden Public Speaking Task. Data were analyzed using regression analysis with clustered bootstrap. The dependent variable was the cortisol area under the curve. Social anxiety and pubertal development scores were decomposed into between- and within-participants components. Between participants, the relation between social anxiety and the cortisol response to public speaking varied with pubertal development: socially anxious individuals showed higher responses at low levels of pubertal development, but lower responses at high levels of pubertal development. Within participants, an increase in social anxiety over time was associated with a lower cortisol response. The results are in line with the suggestion that the responses of socially anxious individuals change from elevated in childhood to attenuated in adolescence and adulthood. Attenuation of the cortisol response is explained by theories proposing that the stress response changes with the duration of the stressor.