Fred Hasselman

Contemporary theories of 1/f noise in motor control

1/f noise has been discovered in a number of time series collected in psychological and behavioral experiments. This ubiquitous phenomenon has been ignored for a long time and classical models were not designed for accounting for these long-range correlations. The aim of this paper is to present and discuss contrasted theoretical perspectives on 1/f noise, in order to provide a comprehensive overview of current debates in this domain. In a first part, we propose a formal definition of the phenomenon of 1/f noise, and we present some commonly used methods for measuring long-range correlations in time series. In a second part, we develop a theoretical position that considers 1/f noise as the hallmark of system complexity. From this point of view, 1/f noise emerges from the coordination of the many elements that compose the system. In a third part, we present a theoretical counterpoint suggesting that 1/f noise could emerge from localized sources within the system. In conclusion, we try to draw some lines of reasoning for going beyond the opposition between these two approaches.

Response to Comment on "Estimating the reproducibility of psychological science"

Gilbert et al. conclude that evidence from the Open Science Collaboration’s Reproducibility Project: Psychology indicates high reproducibility, given the study methodology. Their very optimistic assessment is limited by statistical misconceptions and by causal inferences from selectively interpreted, correlational data. Using the Reproducibility Project: Psychology data, both optimistic and pessimistic conclusions about reproducibility are possible, and neither are yet warranted.

PsychDisclosure.org : Grassroots Support for Reforming Reporting Standards in Psychology.

There is currently an unprecedented level of doubt regarding the reliability of research findings in psychology. Many recommendations have been made to improve the current situation. In this article, we report results from PsychDisclosure.org, a novel open-science initiative that provides a platform for authors of recently published articles to disclose four methodological design specification details that are not required to be disclosed under current reporting standards but that are critical for accurate interpretation and evaluation of reported findings. Grassroots sentiment—as manifested in the positive and appreciative response to our initiative—indicates that psychologists want to see changes made at the systemic level regarding disclosure of such methodological details. Almost 50% of contacted researchers disclosed the requested design specifications for the four methodological categories (excluded subjects, nonreported conditions and measures, and sample size determination). Disclosed information provided by participating authors also revealed several instances of questionable editorial practices, which need to be thoroughly examined and redressed. On the basis of these results, we argue that the time is now for mandatory methods disclosure statements for all psychology journals, which would be an important step forward in improving the reliability of findings in psychology.

An interaction-dominant perspective on reading fluency and dyslexia

The background noise of response times is often overlooked in scientific inquiries of cognitive performances. However, it is becoming widely acknowledged in psychology, medicine, physiology, physics, and beyond that temporal patterns of variability constitute a rich source of information. Here, we introduce two complexity measures (1/f scaling and recurrence quantification analysis) that employ background noise as metrics of reading fluency. These measures gauge the extent of interdependence across, rather than within, cognitive components. In this study, we investigated dyslexic and non-dyslexic word-naming performance in beginning readers and observed that these complexity metrics differentiate reliably between dyslexic and average response times and correlate strongly with the severity of the reading impairment. The direction of change in the introduced metrics suggests that developmental dyslexia resides from dynamical instabilities in the coordination among the many components necessary to read, which could explain why dyslexic readers score below average on so many distinct tasks and modalities.

Benefits of Systematic Phonics Instruction

Systematic-phonics instruction appears to be more effective than nonsystematic phonics instruction for teaching reading (Ehri, Nunes, Stahl, & Willows, 2001). In the present study, a systematic phonics approach was directly compared with a nonsystematic phonics approach for kindergarten children. Both approaches were delivered using computer programs teaching the same Dutch grapheme–phoneme correspondences. Both phonics-trained groups progressed to the same extent on productive letter-sound knowledge compared to the control group. However, on measures of phonemic awareness, spelling, and reading, the systematic phonics group made more progress than the nonsystematic phonics group and the control group.

A trade-off study revealing nested timescales of constraint

This study investigates human performance in a cyclic Fitts task at three different scales of observation, either in the presence (difficult condition) or in the absence (easy condition) of a speed–accuracy trade-off. At the fastest scale, the harmonicity of the back and forth movements, which reflects the dissipation of mechanical energy, was measured within the timeframe of single trials. At an intermediate scale, speed and accuracy measures were determined over a trial. The slowest scale pertains to the temporal structure of movement variability, which evolves over multiple trials. In the difficult condition, reliable correlations across each of the measures corroborated a coupling of nested scales of performance. Participants who predominantly emphasized the speed-side of the trade-off (despite the instruction to be both fast and accurate) produced more harmonic movements and clearer 1/f scaling in the produced movement time series, but were less accurate and produced more random variability in the produced movement amplitudes (vice versa for more accurate participants). This implied that speed–accuracy trade-off was accompanied by a trade-off between temporal and spatial streams of 1/f scaling, as confirmed by entropy measures. In the easy condition, however, no trade-offs nor couplings among scales of performance were observed. Together, these results suggest that 1/f scaling is more than just a byproduct of cognition. These findings rather support the claim that interaction-dominant dynamics constitute a coordinative basis for goal-directed behavior.

Non-linear EEG analyses predict non-response to rTMS treatment in major depressive disorder

OBJECTIVE Several linear electroencephalographic (EEG) measures at baseline have been demonstrated to be associated with treatment outcome after antidepressant treatment. In this study we investigated the added value of non-linear EEG metrics in the alpha band in predicting treatment outcome to repetitive transcranial magnetic stimulation (rTMS). METHODS Subjects were 90 patients with major depressive disorder (MDD) and a group of 17 healthy controls (HC). MDD patients were treated with rTMS and psychotherapy for on average 21 sessions. Three non-linear EEG metrics (Lempel-Ziv Complexity (LZC); False Nearest Neighbors and Largest Lyapunov Exponent) were applied to the alpha band (7-13 Hz) for two 1-min epochs EEG and the association with treatment outcome was investigated. RESULTS No differences were found between a subgroup of unmedicated MDD patients and the HC. Non-responders showed a significant decrease in LZC from minute 1 to minute 2, whereas the responders and HC showed an increase in LZC. CONCLUSIONS There is no difference in EEG complexity between MDD and HC and the change in LZC across time demonstrated value in predicting outcome to rTMS. SIGNIFICANCE This is the first study demonstrating utility of non-linear EEG metrics in predicting treatment outcome in MDD.

Functioning within a relationship: Mother-infant synchrony and infant sleep

The aim of this study was to investigate the coupling of the biological system of infant sleep and the social system of mother-infant synchrony. Before birth and shortly after birth the systems appear to be connected, but it is unclear whether this remains the case over time. This study therefore examined whether infant sleep measured at 6 weeks and 5 months could predict mother-infant gaze synchrony after a social challenge at 5 months (N=84). Infant sleep was measured in terms of sleep bout duration, which normally increases during this period. Gaze was defined in terms of looking at each others head simultaneously, known as gaze synchrony, or looking elsewhere. Results showed that infant sleep could predict the temporal dynamics of the mother-infant interaction in terms of flexibility of gaze pattern shifts. The larger the increase in sleep bout duration over age, the more flexible the interaction appeared to be. Maternal Age, type of feeding and change of feeding appeared to function as confounding variables in this relation. Infant sleep could not predict percentage of synchrony (central tendency measure) or the average sequence length of gaze patterns (temporal dynamic measure).

Integrated Pictorial Mnemonics and Stimulus Fading: Teaching Kindergartners Letter Sounds.

BACKGROUND The conclusion from a vast literature on literacy acquisition is that letter knowledge is one of the best predictors of literacy development. The question of the best way to teach children letter sounds has not, as yet, been answered satisfactorily. AIMS The aim of this study was the evaluation of a computer training program using integrated-picture mnemonics combined with a fading procedure to teach children letter sounds. SAMPLE Thirty-nine kindergartners attending mainstream primary education participated in this study. METHOD A within-subject design was used. Each kindergartner learned letters under three conditions: (a) a fading condition in which letters are taught using a picture-supported first-sound mnemonics procedure in combination with a fading procedure; (b) an embedded condition in which letters are taught using the picture-supported first-sound-mnemonics procedure only and (c) a without-picture condition in which letters are taught using a first-sound procedure without-picture support. Dependent measures included a productive and receptive letter-sound test, and a first-sound isolation task. RESULTS Productive letter-sound knowledge in the fading condition was better than in the other two conditions. In addition, kindergartners with good and those with poor first-sound isolation ability performed equally well in the fading condition. However, in the embedded and in the without-picture conditions, the kindergartners with good first-sound isolation ability outperformed those with poor isolation ability. CONCLUSION These findings indicate that an integrated-picture mnemonics procedure combined with a fading procedure is effective in teaching kindergartners letter sounds and that the success of such a procedure does not depend on their initial first-sound isolation ability.

Justify your alpha

In response to recommendations to redefine statistical significance to P ≤ 0.005, we propose that researchers should transparently report and justify all choices they make when designing a study, including the alpha level.