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Archive for November, 2011

Signe Vangkilde will defend her thesis entitled:

May I have your attention, please? Modulations of Visual Attention in Time and Space.

November 24th at the University of Copenhagen.

The defence will begin at 4 pm and will be conducted in Auditorium 1 Gothersgade 140 and will be evaluated by:

  • Associate Professor, Søren Kyllingsbæk, Department of Psychology, University of Copenhagen, (chairman).
  • Dr. Kathrin Finke, Neuro-cognitive Psychology Unit, Department Psychologie, LMU, Munich, Germany.
  • Professor Lars-Göran Nilsson, Department of Psychology, University of Stockholm, Sweden.

Thesis abstract

This thesis comprises a theoretical review and three empirical investigations of human visual attention aiming to increase our knowledge about the dynamics of visual attention in time and space.

In Study I (Vangkilde, Coull, & Bundesen, 2011) a new empirical paradigm is used to investigate how different levels of attentional intensity, expressed as specific expectations of events to come, influence visual attention. The results provide the first direct demonstration that our expectations of future events influence our attention by modulating the speed with which we process information.

Study II (Vangkilde, Bundesen, & Coull, 2011) investigates the attentional effect of the cholinergic neurotransmitter nicotine by use of the new CombiTVA paradigm, which provides estimates of independent subcomponents of attention. It is shown that acute nicotine in non-smokers and chronic nicotine in smokers enhances the visual threshold of perception but slows down the rate of information processing and compromises selectivity. These results challenge and differentiate the claim of nicotine as cognitive enhancer.

Study III (Vangkilde & Habekost, 2010) is an empirical evaluation of the efficacy of a rehabilitation strategy, prism adaptation, claimed to ameliorate symptoms of visual neglect after right hemisphere brain injuries. The study addresses several methodological problems pertaining to previous investigations of prism adaptation, and it establishes that short-term and long-term beneficial effects of prism adaptation could, in part, be realised through a functionally significant change in eye movements.

In the theoretical review all three investigations are related to the empirical and theoretical framework of a Theory of Visual Attention (TVA; Bundesen, 1990) and its neural interpretation (NTVA; Bundesen, Kyllingsbæk, & Habekost, 2005). Furthermore, it is discussed how the investigations provide information which can help bridge the gap between traditional theories focusing on selectivity and capacity of attention within the spatial domain and a more recent trend emphasising the importance of attentional intensity, which concerns the impact of arousal and the deployment of attention in time.

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Maria Norfang will defend her thesis entitled:

The importance of being relevant. Capturing effects of relevance and contrast in visual selection

November 18th at the University of Copenhagen.

The defence will begin at 1 pm and will be conducted in Auditorium 1 Gothersgade 140 and will be evaluated by:

  • Associate professor, Thomas Habekost, Department of Psychology, University of Copenhagen, (Chairman).
  • Professor, Jan Theeuwes, Cognitive Psychology, Vrije Universiteit, Amsterdam, Netherlands.
  • Professor Bruno Laeng, CSHC, University of Oslo, Norway.

Thesis abstract

Every second, more information reach our eyes than can be processed within the limited capacity of the human brain. We are therefore forced to select among the available information. Attentional mechanisms work to ensure that the most important elements are selected for processing. Both the physical properties of the stimulus and the current goal of the observer influence this selection process. However, it has been widely debated whether both components play a role in the initial allocation of visual attention. This thesis explores the role of contrast and of relevance in initial visual attention through a series of behavioral experiments.

In the first line of experiments, contrast was varied independently from relevance. The data demonstrated that task relevance influenced attention for presentation times down to 20 ms. In addition, feature contrast had a significant effect on report accuracy, despite being completely irrelevant to the task. The data confirmed that both contrast and relevance influence initial attentional selection. Furthermore, an interaction between local feature contrast and task relevance was revealed. In the thesis, a new equation of attentional weights that can account for the observed relation is proposed. In the second line of experiments, the complexity of relevance‐based visual selection was explored. Data from a triple conjunction search revealed that the number of conjunction‐types in a display significantly influence visual attention. This result challenge several existing theories of visual attention. Overall, both lines of experiments point towards overlaps between two of the major theories of visual attention today, namely the Guided Search model and the Theory of Visual Attention.

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