Research themes

Information about our research in terms of main results and findings can be obtained from the Research page. Specifics of research are best presented in our Publications and CVs. Here, a brief overview of the principal research topics can be found. They are listed as follows, but not in any order of priority. We are fascinated by all of them.

1. Research on visual masking: psychophysics and visual cognition. We study metacontrast, object substitution masking, feature binding between objects presented in mutual masking, masking with spatially quantized (pixelated) images, perceptual latency priming by masked targets on subsequent masks, etc. (Key names from our lab and of our colleagues with whome we collaborate and discuss matters of interest: Luiga, Bachmann, Murd, Einberg, Põder, Gellatly, Francis, Breitmeyer, Ögmen, Herzog.)

2. Research on visual masking: cognitive neuroscience. We also study neural correlates of masking effects (ERPs, oscillatory EEG responses investigated by time-frequency analyses), masking by TMS, visual scotomas caused by TMS. In addition to empirical research also a psychophysiological/neurobiological theory of masking called ’perceptual retouch theory’ is being developed (including computational neural models). We have introduced a new paradigm of TMS-masking where TMS is targeted at remote, non-visual cortical areas. (Key names: Bachmann, Kirt, Aru, Murd, Rutiku, Maksimov, Vaht, Harro.)

3. Neural correlates of consciousness. We use different psychological experiments on perception and attention in the context of EEG/ERP registration and/or TMS. We contrast conditions where subjects are aware of the (target) stimuli and where they are unaware of them. By finding what differences in brain processes between these conditions emerge, we aim for finding objective signatures of the processes that make it possible to explicitly perceive visual objects and events. Neural markers of contents of consciousness or neural correlates of consciousness (NCC) are studied. Besides using masking or peri-threshold stimulation, other paradigms such as afterimages, visual search, attentional blink, apparent/real motion, temporal-order judgment have been and are also instrumental for this purpose. We have introduced a new paradigm of TMS-masking where TMS is targeted at remote, non-visual cortical areas while SOA between TMS and modal targets is varied. We have demonstrated detrimental effects of selective attention on consciousness of visual targets. (Key names: Rutiku, Aru, Einberg, Bachmann, Stamm, Murd.)

4. Visual crowding. An otherwise easily discriminable object becomes difficult to discriminate when it is presented among the neighboring distracter objects – this is called crowding. We study the attributes and presentation conditions that predetermine the extent of crowding effects and also develop theoretical models of this effect. (Key names: Põder, Wagemans, Huckauf.)

5. Flash-lag effect. A briefly flashed object when actually presented as aligned with a moving object appears to lag behind the moving one. Similar lag effects are known also for the objects not in motion, but presented in a stream of objects from the same location. We study this phenomenon trying to show that perceptual retouch theory can be used for explaining the flash-lag. (Key names: Bachmann, Põder, Murd, Baldo, Nijhawan.)

6. Visual search and visual spatial attention. We study the effects of stimulus parameters, abrupt singleton onsets, characteristics of pre-cues etc on visual target search and identification. (Key names: Põder, Bachmann, Murd, Luiga.)

7. Perception of in-stream objects. In RSVP streams ob objects, targets undergo various effects such as attentional blink for the second one of the two successive targets, in-stream acceleration of target perception, repetition blindness. We compare in-stream and out-of-stream perception, masking and facilitation effects, etc. (Key names: Hommuk, Bachmann, Sikka.)

8. Perception of spatially quantised (pixelated) and morphed images. Pixelation transform at varying levels of the spatial scale poses difficulties for perceptual discrimination and recognition mechanisms. The typical image transformed in this way used to be human face. We study these effects in different contexts – critical level of pixelation for simple identification, ERP correlates of pixelated object perception, effects of pixelation on attractiveness and other person characteristics evaluation. We also study face-based trait perception. Bachmann published the first internationally distributed book on perception of pixelated images. (Key names: Bachmann, Kahusk, Nurmoja, Rutiku.)

9. State-dependent effects of TMS on brain processes. By varying subject’s states in a task-free manner (e.g., caffeine vs placebo administration, sleep vs wakefulness utilization, task-independent visual backgrounds) we stimulate cortical locations by TMS and examine the effects of state, stimulation locus and stimulation characteristics on the dynamics of the resulting effects. For this purpose, MRI based neuronavigation of TMS pulses combined with EEG/ERP registration is used. Basically, this is a perturbational approach to studying brain dynamics and connectivity (Key names: Bachmann, Rutiku, Aru, Murd, Stamm.)

10. Studying the effects of TMS on various states and behavioral /trait dispositions of the subjects. Utilizing different experimental protocols of TMS (including rTMS protocols) we do research on the effects of artificial brain stimulation on arousal-related states, truthfulness of behavior, etc. (Key names: Karton, Vau, Stamm.)

11. Research on the detection of deception. We use EEG/ERP for this purpose. We also look forward to combine EEG and TMS in order to improve the methods of EEG-based detection of deception. (Key names: Bachmann, Karton.)

Additional research themes are more related to supervising students’ research – advertising message effects, experimental aesthetics, conditioning effects, forensic-psychological studies of memory and perception, appearance based person perception, etc.