Behavioral Account of Attended Stream Enhances Neural Tracking

During the past decade, several studies have identified electroencephalographic (EEG) correlates of selective auditory attention to speech. In these studies, typically, listeners are instructed to focus on one of two concurrent speech streams (the “target”), while ignoring the other (the “masker”). EEG signals are recorded while participants are performing this task, and subsequently analyzed to recover the attended stream. An assumption often made in these studies is that the participant’s attention can remain focused on the target throughout the test. To check this assumption, and assess when a participant’s attention in a concurrent speech listening task was directed toward the target, the masker, or neither, we designed a behavioral listen-then-recall task (the Long-SWoRD test). After listening to two simultaneous short stories, participants had to identify keywords from the target story, randomly interspersed among words from the masker story and words from neither story, on a computer screen. To modulate task difficulty, and hence, the likelihood of attentional switches, masker stories were originally uttered by the same talker as the target stories. The masker voice parameters were then manipulated to parametrically control the similarity of the two streams, from clearly dissimilar to almost identical. While participants listened to the stories, EEG signals were measured and subsequently, analyzed using a temporal response function (TRF) model to reconstruct the speech stimuli. Responses in the behavioral recall task were used to infer, retrospectively, when attention was directed toward the target, the masker, or neither. During the model-training phase, the results of these behavioral-data-driven inferences were used as inputs to the model in addition to the EEG signals, to determine if this additional information would improve stimulus reconstruction accuracy, relative to performance of models trained under the assumption that the listener’s attention was unwaveringly focused on the target. Results from 21 participants show that information regarding the actual – as opposed to, assumed – attentional focus can be used advantageously during model training, to enhance subsequent (test phase) accuracy of auditory stimulus-reconstruction based on EEG signals. This is the case, especially, in challenging listening situations, where the participants’ attention is less likely to remain focused entirely on the target talker. In situations where the two competing voices are clearly distinct and easily separated perceptually, the assumption that listeners are able to stay focused on the target is reasonable. The behavioral recall protocol introduced here provides experimenters with a means to behaviorally track fluctuations in auditory selective attention, including, in combined behavioral/neurophysiological studies.

The Role of Self-dehumanisation in Radicalisation to Peaceful and Violent Political Activism

Taking the significance quest (Kruglanski et al., 2014) approach to radicalisation, this dissertation examined if self-dehumanisation could explain why some people turn to violent radicalism and others to peaceful activism to restore significance in life. I hypothesised that significance loss induces self-dehumanisation which subsequently warrants political violence. Study 1, a cross-sectional online study (N = 183), tested the mediating effect of self-dehumanisation on the relationship between significance loss and radicalism/activism. Study 2, an experimental online study with a between-subjects design (N = 264) where significance loss was manipulated using a recall task examined the causal links between significance loss and radicalism/activism, additionally testing the moderating effects of group vs. individual significance loss on this association. Study 1 demonstrated positive links between significance loss and peaceful activism, violent radicalism and self-dehumanisation. Dehumanising oneself was negatively related to peaceful activism; no support was found for its association with violent radicalism intentions. Study 2 showed the causal role of significance loss in enhancing peaceful activism and violent radicalism. The moderating effect of group vs. individual significance loss was not supported. This dissertation contributes to knowledge on the mechanisms of radicalisation, demonstrating self-dehumanisation’s activism-suppressing role for the first time.

Validation of a novel fully automated story recall task for repeated remote high-frequency administration

INTRODUCTION: Longitudinal data is key to identifying cognitive decline and treatment response in Alzheimer's disease (AD). METHODS: The Automatic Story Recall Task (ASRT) is a novel, fully automated test that can be self-administered remotely. In this longitudinal case-control observational study, 151 participants (mean age: 69.99 (range 54-82), 73 mild cognitive impairment/mild AD and 78 cognitively unimpaired) completed parallel ASRT assessments on their smart devices over 7-8 days. Responses were automatically transcribed and scored using text similarity metrics. RESULTS: Participants reported good task usability. Adherence to optional daily assessment was moderate. Parallel forms correlation coefficients between ASRTs were moderate-high. ASRTs correlated moderately with established tests of episodic memory and global cognitive function. Poorer performance was observed in participants with MCI/Mild AD. DISCUSSION: Unsupervised ASRT assessment is feasible in older and cognitively impaired people. This automated task shows good parallel forms reliability and convergent validity with established cognitive tests.

Viewing Nature Lets Your Mind Run Free: Three Experiments about the Influence of Viewing a Nature Video on Cognitive Coping with Psychological Distress

Viewing nature has restorative qualities that might help people cope with their personal struggles. Three lab experiments (N = 506) studied whether environment (nature vs. built) influences cognitive coping with psychological distress. Psychological distress was induced with an autobiographical recall task about serious regret, whereafter participants were randomly assigned to view a nature or built video. Cognitive coping (i) Quantity, (ii) Content, and (iii) Quality were hereafter assessed as well as extent and vividness of the regretful memory during the video. Results showed a higher cognitive coping Quantity (Study 1 and 3) and a higher cognitive coping Quality (All studies) for the nature (vs. built) condition. Regarding cognitive coping Content, results varied across the studies. Additionally, participants reported to have thought about the experienced psychological distress to a greater extent while viewing the nature (vs. built) video. Yet they did rate viewing nature as more relaxing. We propose a two-step pathway as an underlying mechanism of restoration. In the first step the capacity for directed attention replenishes. Secondly, this renewed capacity is directed towards internal processes, creating the optimal setting for reflection. Hence, viewing nature allows people to truly process whatever is occupying their minds, which is ultimately relieving and beneficial for mental health.

Language Shift Effect on Memory Generalization of Chinese-English Bilinguals

Language shift occurs when people learn information in one language but recall it in another language. This mismatch between encoding and retrieval language is found to impair memory accuracy when memory is tested immediately after learning. However, does the observed language shift effect still exist after a certain period of delay? Would it influence other aspects of memory, especially memory generalization? To address these two questions, we performed a memory experiment among unbalanced Chinese-English bilinguals. In the experiment, participants were required to read two stories (one in English, one in Chinese) and to retell the stories in Chinese from their memories afterward. Delay interval was manipulated in the experiment where participants either took memory recall tests immediately after story-reading or after 24 hours' delay. To analyze memory generalization, we coded the generalized words participants used to retell the stories. The results suggest that language shift (encoding in English and retrieving in Chinese) leads to a more generalized description in a memory recall task. However, the observed language shift effect disappears after 24 hours' delay. It can be concluded that language shift impacts bilingual learners' memory generalization in immediate recall tests, but such effect disappears after 24 hours' delay, which indicates the key role of delay interval in modulating language shift effect.

PHONOLOGICAL PROCESSING OF STRESS BY NATIVE ENGLISH SPEAKERS LEARNING SPANISH AS A SECOND LANGUAGE

One feature of Spanish that presents some difficulties to second language (L2) learners whose first language (L1) is English concerns lexical stress. This study explores one aspect of the obstacle these learners face, weak phonological processing routines concerning stress inherited from their native language. Participants were L1 English L2 learners of Spanish. The experiment was a sequence-recall task with auditory stimuli minimally contrasting in stress (target) or segmental composition (baseline). The results suggest that learners are more likely to accurately recall sequences with stimuli contrasting in segmental composition than stress, suggesting reduced phonological processing of stress relative to a processing baseline. Furthermore, an increase in proficiency—assessed by means of grammatical and lexical tests—was found to be modestly associated with an increase in the accuracy of processing stress. We conclude that the processing routines of native English speakers lead to an acquisitional obstacle when learning Spanish as a L2.

Recall of Reverberant Speech in Quiet and Four-Talker Babble Noise

Using behavioral evaluation of free recall performance, we investigated whether reverberation and/or noise affected memory performance in normal-hearing adults. Thirty-four participants performed a free-recall task in which they were instructed to repeat the initial word after each sentence and to remember the target words after each list of seven sentences, in a 2 (reverberation) × 2 (noise) factorial design. Pupil dilation responses (baseline and peak pupil dilation) were also recorded sentence-by-sentence while the participants were trying to remember the target words. In noise, speech was presented at an easily audible level using an individualized signal-to-noise ratio (95% speech intelligibility). As expected, recall performance was significantly lower in the noisy environment than in the quiet condition. Regardless of noise interference or reverberation, sentence- baseline values gradually increased with an increase in the number of words to be remembered for a subsequent free-recall task. Long reverberation time had no significant effect on memory retrieval of verbal stimuli or pupillary responses during encoding.

Sequence learning recodes cortical representations instead of strengthening initial ones

We contrast two computational models of sequence learning. The associative learner posits that learning proceeds by strengthening existing association weights. Alternatively, recoding posits that learning creates new and more efficient representations of the learned sequences. Importantly, both models propose that humans act as optimal learners but capture different statistics of the stimuli in their internal model. Furthermore, these models make dissociable predictions as to how learning changes the neural representation of sequences. We tested these predictions by using fMRI to extract neural activity patters from the dorsal visual processing stream during a sequence recall task. We observed that only the recoding account can explain the similarity of neural activity patterns, suggesting that participants recode the learned sequences using chunks. We show that associative learning can theoretically store only very limited number of overlapping sequences, such as common in ecological working memory tasks, and hence an efficient learner should recode initial sequence representations.

Emotion matters

Recent theories and neural models of co-speech gesture have extensively considered its cognitive role in language comprehension but have ignored the emotional function. We investigated the integration of speech and co-speech gestures in memory for verbal information with different emotional connotations (either positive, negative, or neutral). In a surprise cued-recall task, gesture boosted memory for speech with all three emotional valences. Interestingly, gesture was more likely to become integrated into memory of neutrally and positively valenced speech than negatively valenced speech. The results suggest that gesture-speech integration is modulated by emotional valence of speech, which has implications for the emotional function of gesture in language comprehension.