• Visual Attention
  • Visual Perception
  • Visual Working Memory
  • Temporal Integration
  • Perceptual Grouping
  • Cocoa Flavanols

Education & Training

  • Ph.D. 2020

    Cognitive Neuroscience

    Rijksuniversiteit Groningen, Groningen, the Netherlands

  • M.A. 2015

    Experimental Psychology

    Brooklyn College, City University of New York, NY, the US

  • B.A. 2011


    Ankara University, Ankara, Turkey

Academic Positions

  • 2020 2022

    Postdoctoral Researcher

    Rijksuniversiteit Groningen

  • 2015 2020


    Rijksuniversiteit Groningen

  • 2014 2015

    Lab assistant

    Animal vision lab, Brooklyn College, CUNY

Honors, Awards and Grants

  • 2012-2019
    Scholarship from the Ministry of Education, Turkey
    Scholarship covering both masters and PhD programs in the field of experimental psychology from the Ministry of Education, Turkey.

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Two faces of perceptual awareness during the attentional blink: Gradual and discrete

Karabay, A., Wilhelm, S. A., de Jonge, J., Wang, J., Martens, S., & Akyürek, E. G.
Journal Paper Journal of Experimental Psychology: General. (in press)


In a series of experiments, the nature of perceptual awareness during the attentional blink was investigated. Previous work has considered the attentional blink as a discrete, all-or-none phenomenon, indicative of general access to conscious awareness. Using continuous report measures in combination with mixture modeling, the outcomes showed that perceptual awareness during the attentional blink can be a gradual phenomenon. Awareness was not exclusively discrete, but also exhibited a gradual characteristic whenever the spatial extent of attention induced by the first target spanned more than a single location. Under these circumstances, mental representations of blinked targets were impoverished, but did approach the actual identities of the targets. Conversely, when the focus of attention covered only a single location, there was no evidence for any partial knowledge of blinked targets. These two different faces of awareness during the attentional blink challenge current theories of both awareness and temporal attention, which cannot explain the existence of gradual awareness of targets during the attentional blink. To account for the current outcomes, an adaptive gating model is proposed that casts awareness on a continuum between gradual and discrete, rather than as being of either single kind.

Acute effects of cocoa flavanols on visual working memory: Maintenance and updating

Altinok, A., Karabay, A., & Akyürek, E. G.
Journal Paper European Journal of Nutrition. (in press)


Background: Consumption of cocoa flavanols may have acute physiological effects on the brain due to their ability to activate nitric oxide synthesis. Nitric oxide mediates vasodilation, which increases cerebral blood flow, and can also act as a neurotransmitter.

Objectives: This study aimed to examine whether cocoa flavanols have an acute influence on visual working memory (WM).

Methods: Two randomised, double-blind, baseline- and placebo-controlled, counterbalanced crossover experiments were conducted on normal healthy young adult volunteers (NExp1=48 and NExp2=32, gender-balanced). In these experiments, 415 mg cocoa flavanols have been administered to show its acute effects on visual working memory. In the first experiment, memory recall precision was measured in a task that required only passive maintenance of grating orientations in WM. In the second experiment, recall was measured after active updating (mental rotation) of WM contents. Habitual daily flavanols intake, body mass index, and gender were also considered in the analysis.

Results: The results suggested that neither passive maintenance in visual WM nor active updating of WM was acutely enhanced by consumption of cocoa flavanols. Exploratory analyses with covariates (body mass index and daily flavanols intake), and the between-factor of gender also showed no evidence for effects of cocoa flavanols, neither in terms of reaction time, nor accuracy.

Conclusions: Overall, cocoa flavanols did not improve visual working memory recall performance during maintenance, nor did it improve recall accuracy after memory updating.

The effects of long-term intake of cocoa flavanols on cognitive functions and mood, and the physiological mechanisms underlying these effects: A literature review

Karataş, O., Karabay, A., & Alıcı, T.
Review Paper Turkish Psychological Articles. (in press)


In recent years, the health benefits of flavanol-rich cocoa and cocoa-derived products, including on the nervous system, have been clearly demonstrated. The purpose of this review is to summarize randomized controlled trials examining the effects of long-term cocoa flavanols intake on mood and various cognitive functions, such as executive functions, attention, and memory, as well as to discuss mechanisms underlying these effects. In vivo and in vitro studies conducted with humans and experimental animals show that cocoa flavanols improve cognitive functions and mood by increasing the bioavailability of nitric oxide, which has a variety of functions, including dilating blood vessels, acting as a neurotransmitter, and improving insulin sensitivity. Furthermore, strong evidence has been presented that cocoa flavanols, which have a high antioxidant activity and neuroprotective properties, could support cognitive functions in cognitively intact individuals and prevent cognitive decline that inevitably occurs with aging through direct actions on receptors, enzymes, and signaling pathways. Despite the mixed findings observed in cocoa flavanols studies, long-term intake of cocoa flavanols, depending on the dose and duration of administration, regulate mood and support various cognitive functions, such as attention, processing speed, and working memory.

Discriminating global orientation of two element sets

Karabay, A. & Kurylo, D. D.
Journal Paper Journal of Cognition, Volume 3, pp 1-13 (2020)


Perceived global organization of visual patterns is based upon the aggregate contribution of constituent components. Patterns constructed from multiple sources cooperate or compete for global organization. An investigation was made here of interactions between two interspersed element sets on global orientation. It was hypothesized that each set would operate as an integrated unit, and contribute independently to global orientation. Participants viewed a 10 x 10 array of Gabor patches, and indicated the predominant orientation of the array. In Experiment 1 8 all elements were rotated. Rotation up to 23° had little effect, whereas greater rotation produced a progressive shift on global orientation. In Experiment 2 a proportion of elements remained aligned while remaining elements were rotated. Embedding a proportion of aligned elements stabilized global orientation, which was dependent upon the proportion of aligned elements. Specifically, with 20% alignment, global orientation was similar to rotating all elements, whereas 80% alignment strongly biased perception towards aligned elements. The stabilizing effect varied with rotation of the second element set. Across levels of rotation, alignment effects rose to a peak then declined as element sets became orthogonal. In Experiment 3, each element set was rotated independently. Independent rotation of both sets altered global orientation, compressing the psychometric function for the single-element condition. Together, for interspersed element sets with explicit orientations, each set does not contribute independently to global orientation. Instead, element sets interact, where the contribution of one set, presented at a fixed rotation and fixed proportion, varies with the change to the second set.

From stimulus to tepresentation: Target identification in rapid serial visual presentation

Karabay, A.
PhD thesis (2020)

From stimulus to tepresentation: Target identification in rapid serial visual presentation

This dissertation investigated the relationship between target identification and temporal integration with three studies. Rapid serial visual presentation tasks were used to investigate empirical questions, where two targets are embedded in a set of distracters, and the task is to identify targets. Temporal integration is a phenomenon that temporally separated targets fall into the same perceptual episode. The first study investigated whether a change in low-level stimulus features (color/contrast) influences temporal attention and integration. The results showed that a categorical change of target color decreases the competition between targets resulting in better target identification and more frequent integrations. Besides, the study confirmed the literature that high contrast stimuli mask low contrast stimuli if their temporal proximity is close. The second study investigated if Gestalt properties influence the temporal binding of targets and target identification. In addition to studies that show parts of objects are grouped in space, the second study showed that if temporally separated targets form a figure, their integrated percepts and identifications are facilitated. Lastly, how a change in mental state with consumption of cocoa flavanols, which increases blood flow in brain arteries, influences target identification and integrations were investigated. There was no effect of cocoa flavanols on temporal attention and integration. In addition, the study showed that cocoa flavanols improve the efficiency of visual search. In sum, target identification and integration are both influenced by exogenous stimuli properties and by flavanol-induced changes in mental state, and often also in a similar direction.

Temporal integration and attentional selection of color and contrast target pairs in rapid serial visual presentation

Karabay, A. & Akyürek, E.G.
Journal Paper Acta Psychologica, Volume 196, pp 56-69 (2019)


Performance in a dual target rapid serial visual presentation task was investigated, dependent on whether the color or the contrast of the targets was the same or different. Both identification accuracy on the second target, as a measure of temporal attention, and the frequency of temporal integration were measured. When targets had a different color (red or blue), overall identification accuracy of the second target and identification accuracy of the second target at Lag 1 were both higher than when targets had the same color. At the same time, increased temporal integration of the targets at Lag 1 was observed in the different color condition, even though actual (non-integrated) single targets never consisted of multiple colors. When the color pairs were made more similar, so that they all fell within the range of a single nominal hue (blue), these effects were not observed. Different findings were obtained when contrast was manipulated. Identification accuracy of the second target was higher in the same contrast condition than in the different contrast condition. Higher identification accuracy of both targets was furthermore observed when they were presented with high contrast, while target contrast did not influence temporal integration at all. Temporal attention and integration were thus influenced differently by target contrast pairing than by (categorical) color pairing. Categorically different color pairs, or more generally, categorical feature pairs, may thus afford a reduction in temporal competition between successive targets that eventually enhances attention and integration.

The acute effects of cocoa flavanols on temporal and spatial attention

Karabay, A., Saija, J., Field, D., & Akyürek, E.G.
Journal Paper Psychopharmacology, Volume 235, Issue 5, pp 1497–1511 (2018)


In this study, we investigated how the acute physiological effects of cocoa flavanols might result in specific cognitive changes, in particular in temporal and spatial attention. To this end, we pre registered and implemented a randomized, double-blind, placeboand baseline-controlled crossover design. A sample of 48 university students participated in the study and each of them completed the experimental tasks in four conditions (baseline, placebo, low dose, and high-dose flavanol), administered in separate sessions with a 1-week washout interval. A rapid serial visual presentation task was used to test flavanol effects on temporal attention and integration, and a visual search task was similarly employed to investigate spatial attention. Results indicated that cocoa flavanols improved visual search efficiency, reflected by reduced reaction time. However, cocoa flavanols did not facilitate temporal attention nor integration, suggesting that flavanols may affect some aspects of attention, but not others. Potential underlying mechanisms are discussed.

The effects of Kanizsa contours on temporal integration and attention in rapid serial visual presentation

Karabay, A. & Akyürek, E.G.
Journal Paper Attention, Perception, & Psychophysics, Volume 79, Issue 6, pp 1742–1754 (2017)


Performance in rapid serial visual presentation tasks has been shown to depend on the temporal integration of target stimuli when they are presented in direct succession. Temporal target integration produces a single, combined representation of visually compatible stimuli, which is comparatively easy to identify. It is currently unknown to what extent target compatibility affects this perceptual behavior, because it has not been studied systematically to date. In the present study, the effects of compatibility on temporal integration and attention were investigated by manipulating the Gestalt properties of target features. Of particular interest were configurations in which a global illusory shape was formed when all stimulus features were present; a Kanizsa stimulus, which was expected to have a unifying effect on the perception of the successive targets. The results showed that although the presence of a Kanizsa shape can indeed enhance temporal integration, this also was observed for other good Gestalts, such as due to common fate and closure. Identification accuracy seemed to vary, possibly as a result of masking strength, but this did not seem associated with attentional processing per se. Implications for theories of Gestalt processing and temporal integration are discussed.

Herkes icin istatistiksel programlama ve analiz (Introduction to R)

Richard Cotton, translated to Turkish by Sünbül, Ö., Sünbül, S.Ö., & Karabay, A.
Book translation Pegem Academy Press, Istanbul, Turkey (2020)

Herkes icin istatistiksel programlama ve analiz

R istatistiksel programlama ve analiz için geliştirilmiş olan güçlü bir programlama dilidir. Yurtdışında yaygın olarak kullanılmakta ve birçok üniversitede lisansüstü ders olarak okutulmaktadır. Bu programlama dili açık kaynak kodlu olduğundan dolayı programa rahatlıkla ulaşılabilmektedir ve program ücretsiz olarak kullanılabilmektedir. R istatistiksel analize ihtiyaç duyulan hemen hemen bütün bilim alanlarında (sosyal, sağlık, fen, ekonomi vb.) kullanılabilmektedir. R, çok geniş bir kütüphaneye sahiptir ve bu kütüphane gün geçtikçe artan bir ivmeyle gelişmeye devam etmektedir. R'ın yakın bir gelecekte popüler istatistiksel programların yerini alacağı düşünülmektedir. Kitabın içeriği basitten karmaşığa doğru olacak şekilde adım adım kurgulanmıştır. Herhangi bir programlama dili deneyimine sahip olmayan bireylerin dahi rahatlıkla istatistiksel programlama ve analiz yapmasına olanak sağlamaktadır.

The Attentional Blink: Binary Or Gradual?

Karabay, A., Wang, J., Martens, S., & Akyürek, E. G.
Talk21st Conference of the European Society for Cognitive Psychology (ESCoP) in Tenerife, Spain. (2019)


Identification of the second of two targets (T2) is difficult when it follows the first one within 200-500 milliseconds. This so-called attentional blink (AB) may reflect that a missed T2 fails to reach post-perceptual processing. Alternatively, T2 may still reach working memory partially, or in a degraded fashion. To arbitrate between these possibilities, we applied mixture modeling to continuous target features (e.g., orientation). If T2 does not reach post-perceptual processing, responses should be random guesses, that is, uncorrelated with the target. If the T2 representation is only degraded, then errors should cluster around the target with a certain precision. We observed notable differences in AB tasks that are spatially variable and those that are not. In non-spatial tasks, T2 identification was binary; it either did or did not reach post-perceptual processing. In spatial tasks, however, T2 identification was graded, suggesting it was represented in working memory, but with decreased precision.

Decoding Sensory and Abstract Information From Activity Silent Brain States

Kandemir, G., Karabay, A., & Akyürek, E. G.
Talk21st Conference of the European Society for Cognitive Psychology (ESCoP) in Tenerife, Spain. (2019)


Distributed Working Memory (WM) models attribute different levels of WM representations to different regions of the brain. One highly debated factor is whether the information represented in different levels is retained via similar mechanisms. Recently it was shown that sensory information was maintained in activity-silent form and that the state of the network could be revealed following a perturbation by the presentation of a non-informative signal (impulse signal). We applied the same perturbation technique to representations in visual WM, which either corresponded to directly presented orientation gratings, or to stimuli that were recoded following abstract task rules that consisted of rotation instructions. The decoding of EEG recordings revealed that abstract task rules were also retained in activity-silent form and that the impulse signal boosted decoding accuracy during the activity-silent WM maintenance phase. Furthermore, the imagined orientations that were the product of the rotation task were also decodable from impulse-driven activity.

The Acute Effects Of Cocoa Flavanols On Visual Working Memory

Altınok, A., Karabay, A., & Akyürek, E.G.
Poster21st Conference of the European Society for Cognitive Psychology (ESCoP) in Tenerife, Spain. (2019)


Consumption of cocoa flavanols may have beneficial physiological effects on the brain due to their ability to activate nitric oxide synthesis. Nitric oxide mediates vasodilation, increasing cerebral blood flow, and can also act as a neurotransmitter. However, the cognitive consequences of cocoa flavanols remain underspecified. The aim of this study was to examine whether cocoa flavanols influence visual working memory (WM). We conducted two randomised, within-subjects, placebo controlled, double-blind experiments on normal healthy adult volunteers (N=48 and N=36, gender-balanced). In the first experiment, we measured passive maintenance of grating orientations in WM, whereas in the second experiment we measured active updating of WM (rotation). Precision and guess rates were analysed with MemToolBox. The results suggested that passive maintenance in visual WM is not enhanced by cocoa flavanols, possibly because it relies on activity-silent (synaptic) mechanisms. By contrast, preliminary results indicate that active updating of WM is affected by cocoa flavanols.

Decoding Visual Working Memory Before and After Mental Operations

Kandemir, G. Karabay, A., & Akyürek, E.G.
PosterBCN Winter Meeting at the University of Twente in Twente, Netherlands. (2019)

The Acute Effects of Cocoa Flavanols on Temporal and Spatial Attention

Karabay, A., Saija J., David F., & Akyürek, E.G.
Talkwinter conference 2017 of De Nederlandse Vereniging voor Psychonomie in Egmond, Netherlands. (2017)

Target Color and Contrast Influences Temporal Attention in Rapid Serial Visual Presentations

Karabay, A.& Akyürek, E.G.
Poster20th Conference of the European Society for Cognitive Psychology (ESCoP) in Potsdam, Germany. & 40th European Conference on Visual Perception (ECVP) in Berlin, Germany. (2017) & Psychonomics International Meeting in Amsterdam. (2018)


Attentional blink (AB) is a phenomenon that identifying the second target (T2) stimulus is restricted when it follows the first target (T1) with a short interval (200-500 ms). Various factors modulate AB; in this study, we investigated how target (I) colors and (II) contrast influence temporal attention. Attentional blink/temporal integration task was adapted to study in order to test how different color/contrast pairs influence T2| T1 accuracy and temporal integration. There were two color/contrast conditions: single color/contrast (T1 and T2 colors/contrast matched), mixed color/contrast (T1 and T2 were different colors/contrast). (I) It is found that T2| T1 accuracy were higher in single color condition. Further color specific analysis showed that T1 and T2 accuracy was high when target color was red and T2| T1 identification was greater when T2 color was red. Moreover, greater integration was observed in mixed color condition. It is a surprising finding since targets did not contain multiple colors in any trials. (II) There was no difference between single and mixed contrast condition on T2| T1 accuracy and temporal integration. Greater T1 and T2 accuracy was observed when targets were in high contrast condition. Better T2| T1 identification was observed in the high contrast T2 condition. On the contrary, integration was affected by T2 contrast, and more integration was observed when T2 contrast was low. In conclusion, (I) temporal attention was influenced by target color-pair conditions; however (II) contrast condition does not influence temporal attention in the same way color-pairs does.

Kanizsa Effects on Temporal Integration and Attention

Karabay, A.& Akyürek, E.G.
PosterHeymans symposium at the Rijksuniversiteit Groningen in Groningen, Netherlands. (2017)

Perceptual Grouping by Orientation Coherence

Karabay, A.& Kurylo, D.
PosterScience Day, Brooklyn College in NY, the US. (2015)


Perceptual grouping allows the unification of elements within complex visual scenes. Perceptual grouping can be based upon several relationships among stimulus elements, including common orientation. Grouping can be disrupted by introducing noise elements, which disengage binding among target elements. We investigated parameters that limit grouping by interferencefrom noise. Specifically, we determined (1) the level of deviation of noise elements and (2) proportion of noise-target elements required to break perceptual grouping.It was hypothesized that 45° deviation of noise elements is required before disruption is apparent, since 45°borders the level of rotation oriented towards an opposing grouping pattern. It was further hypothesized that stimuli exceeding 50% noise elements will disrupt perceptual grouping, since the dominant grouping pattern will be carried by noise elements. In order to test these hypotheses, we measured visual discrimination of visual patterns. Four subjects indicated the dominant grouping pattern (horizontal or vertical) of an array of Gabor patches (oriented gratings). Measurements were made at five levels of orientation coherence and six levels deviation of noise elements. Backward masking was used to limit processing time of the stimulus.Results showed that perceptual grouping decreased significantly (from 95% to 67%) in the 45° of deviation condition. With 60% noise elements,discrimination was reduced to chance (52%). These results indicate that noise serves to reverse perceived grouping when presented at magnitudes or proportions that dominate constituents of stimulus patterns.