University of Groningen, Groningen, the Netherlands
University of Groningen, Groningen, the Netherlands
Brooklyn College, City University of New York, NY, the US
Ankara University, Ankara, Turkey
University of Groningen, Departmant of Experimental Psychology
Animal vision lab, Brooklyn College, City University of New York
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.
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.
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.
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.
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.
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