Honors & Awards

  • Travel Award, Department of Women's and Children's Health at Karolinska Institutet (2017)
  • Santander Universities Scholarship, Santander/Durham University (2013)
  • CONACYT Graduate Fellowship, COSCYT-CONACYT (Mexican National Council of Science and Technology) (2013)

Professional Education

  • Licenciado, Universidad De Monterrey (2010)
  • Diploma, Universidad De Barcelona (2013)
  • Master of Science, Durham University (2015)
  • Doctor of Philosophy, Karolinska Institutet (2020)

All Publications

  • Visual disengagement in young infants in relation to age, sex, SES, developmental level and adaptive functioning. Infant behavior & development Siqueiros Sanchez, M., Ronald, A., Mason, L., Jones, E. J., Bolte, S., Falck-Ytter, T. 2021; 63: 101555


    Visual attention plays a key role in infants' interaction with the environment, and shapes their behavioral and brain development. As such, early problems with flexibly switching gaze from one stimulus to another (visual disengagement) have been hypothesized to lead to developmental difficulties (e.g. joint attention and social skills) over time. This study aimed to identify cross-sectional associations between performance in the Gap task (gaze shift latencies and visual attention disengagement) and measures of development and adaptive behavior in conjunction to any sex or socioeconomic status effects in infancy. We measured visual attention disengagement in 436 5-month-old infants and calculated its association with cognitive developmental level, adaptive behaviours, socioeconomic status (SES) and biological sex. In the Gap task, participants must redirect their gaze from a central stimulus to an appearing peripheral stimulus. The three experimental conditions of the task (Gap, Baseline and Overlap) differ on the timepoint when the central stimuli disappears in relation to the appearance of the peripheral stimulus: 200 ms before the peripheral stimulus appears (Gap), simultaneously to its appearance (Baseline), or with peripheral stimulus offset (Overlap). The data from the experimental conditions showed the expected pattern, with average latencies being the shortest in the Gap and longest in the Overlap condition. Females were faster (p = .004) than males in the Gap condition, which could indicate that arousal-related effects differ as a function of biological sex. Infants from higher SES were slower (p = .031) in the Overlap condition compared to lower SES infants. This suggests that basic visual attention may differ by socio-cultural background, and should be considered when studying visual attention and its developmental correlates. We observed no significant association to concurrent developmental level or adaptive function. Given its large sample size, this study provides a useful reference for future studies of visual disengagement in early infancy.

    View details for DOI 10.1016/j.infbeh.2021.101555

    View details for PubMedID 33799012

  • Visual Disengagement: Genetic Architecture and Relation to Autistic Traits in the General Population JOURNAL OF AUTISM AND DEVELOPMENTAL DISORDERS Sanchez, M., Pettersson, E., Kennedy, D. P., Bolte, S., Lichtenstein, P., D'Onofrio, B. M., Falck-Ytter, T. 2020; 50 (6): 2188–2200


    Visual disengagement has been hypothesized as an endophenotype for autism. In this study we used twin modelling to assess the role of genetics in basic measures of visual disengagement, and tested their putative association to autistic traits in the general population. We used the Gap Overlap task in a sample of 492 twins. Results showed that most of the covariance among eye movement latencies across conditions was shared and primarily genetic. Further, there were unique genetic contributions to the Gap condition, but not to the Overlap condition-i.e. the one theorized to capture visual disengagement. We found no phenotypic association between autistic traits and disengagement, thus not supporting the hypothesis of visual disengagement as an endophenotype for autistic traits.

    View details for DOI 10.1007/s10803-019-03974-6

    View details for Web of Science ID 000536416800026

    View details for PubMedID 30859356

    View details for PubMedCentralID PMC7261271

  • Volitional eye movement control and ADHD traits: a twin study JOURNAL OF CHILD PSYCHOLOGY AND PSYCHIATRY Siqueiros Sanchez, M., Falck-Ytter, T., Kennedy, D. P., Bolte, S., Lichtenstein, P., D'Onofrio, B. M., Pettersson, E. 2020; 61 (12): 1309–16


    Top-down volitional command of eye movements may serve as a candidate endophenotype of ADHD, an important function underlying goal-directed action in everyday life. In this twin study, we examined the relation between performance on a response inhibition eye-tracking paradigm and parent-rated ADHD traits in a population-based twin sample. We hypothesized that altered eye movement control is associated with the severity of ADHD traits and that this association is attributable to genetic factors.A total of 640 twins (320 pairs, 50% monozygotic) aged 9-14 years) from the Child and Adolescent Twin Study in Sweden (CATSS) participated. Twins performed the antisaccade task indexing inhibitory alterations as either direction errors (following exogenous cues rather than instructions) or premature anticipatory eye movements (failure to wait for cues). We calculated the associations of eye movement control and ADHD traits using linear regression mixed-effects models and genetic and environmental influences with multivariate twin models.Premature anticipatory eye movements were positively associated with inattentive traits (β = .17; 95% CI: 0.04, 0.31), while controlling for hyperactive behaviors and other covariates. Both premature anticipatory eye movements and inattention were heritable (h2  = 0.40, 95% CI: 0.22, 0.56; h2  = 0.55; 95% CI: 0.42, 0.65; respectively), and their genetic correlation was small but statistically significant (r = .19, 95% CI: 0.02, 0.36). However, the genetic correlation did not remain significant after adjusting for covariates (age, sex, hyperactivity traits, IQ). No link was found between direction errors and ADHD traits.This study indicates that there is a specific, genetically influenced, relation between top-down eye movement control and the inattentive traits typical of ADHD.

    View details for DOI 10.1111/jcpp.13210

    View details for Web of Science ID 000511008500001

    View details for PubMedID 32020616

    View details for PubMedCentralID PMC7754462

  • The Babytwins Study Sweden (BATSS): A Multi-Method Infant Twin Study of Genetic and Environmental Factors Influencing Infant Brain and Behavioral Development. Twin research and human genetics : the official journal of the International Society for Twin Studies Falck-Ytter, T., Hamrefors, L., Siqueiros Sanches, M., Portugal, A. M., Taylor, M., Li, D., Viktorsson, C., Hardiansyah, I., Myers, L., Westberg, L., Bolte, S., Tammimies, K., Ronald, A. 2021: 1-11


    Twin studies can help us understand the relative contributions of genes and environment to phenotypic trait variation, including attentional and brain activation measures. In terms of applying methodologies such as electroencephalography (EEG) and eye tracking, which are key methods in developmental neuroscience, infant twin studies are almost nonexistent. Here, we describe the Babytwins Study Sweden (BATSS), a multi-method longitudinal twin study of 177 MZ and 134 DZ twin pairs (i.e., 622 individual infants) covering the 5-36 month time period. The study includes EEG, eye tracking and genetics, together with more traditional measures based on in-person testing, direct observation and questionnaires. The results show that interest in participation in research among twin parents is high, despite the comprehensive protocol. DNA analysis from saliva samples was possible in virtually all participants, allowing for both zygosity confirmation and polygenic score analyses. Combining a longitudinal twin design with advanced technologies in developmental cognitive neuroscience and genomics, BATSS represents a new approach in infancy research, which we hope to have impact across multiple disciplines in the coming years.

    View details for DOI 10.1017/thg.2021.34

    View details for PubMedID 34521499

  • Determining Zygosity in Infant Twins - Revisiting the Questionnaire Approach. Twin research and human genetics : the official journal of the International Society for Twin Studies Hardiansyah, I., Hamrefors, L., Siqueiros, M., Falck-Ytter, T., Tammimies, K. 2021; 24 (3): 168-175


    Accurate zygosity determination is a fundamental step in twin research. Although DNA-based testing is the gold standard for determining zygosity, collecting biological samples is not feasible in all research settings or all families. Previous work has demonstrated the feasibility of zygosity estimation based on questionnaire (physical similarity) data in older twins, but the extent to which this is also a reliable approach in infancy is less well established. Here, we report the accuracy of different questionnaire-based zygosity determination approaches (traditional and machine learning) in 5.5 month-old twins. The participant cohort comprised 284 infant twin pairs (128 dizygotic and 156 monozygotic) who participated in the Babytwins Study Sweden (BATSS). Manual scoring based on an established technique validated in older twins accurately predicted 90.49% of the zygosities with a sensitivity of 91.65% and specificity of 89.06%. The machine learning approach improved the prediction accuracy to 93.10%, with a sensitivity of 91.30% and specificity of 94.29%. Additionally, we quantified the systematic impact of zygosity misclassification on estimates of genetic and environmental influences using simulation-based sensitivity analysis on a separate data set to show the implication of our machine learning accuracy gain. In conclusion, our study demonstrates the feasibility of determining zygosity in very young infant twins using a questionnaire with four items and builds a scalable machine learning model with better metrics, thus a viable alternative to DNA tests in large-scale infant twin studies.

    View details for DOI 10.1017/thg.2021.24

    View details for PubMedID 34247691