Perception

The objective of this study was to investigate the effect of tilting a frame on the perceptual organization in random dot patterns. Ten random patterns of nine dots were generated. For each pattern, a square frame was tilted at seven angles around the dots. Ten observers were asked to indicate the groups of dots in each stimulus. Each stimulus was seen 4 times by each observer which enabled us to study within-subject consistencies provided grouping reports. Within- and between-subject consistencies were computed to study if the responses provided by participants were consistent and thus reliable. The dominant group was defined as the most repeated group in all 40 reports (10 participants, 4 repetitions) obtained for each stimulus. We studied how tilting a frame affected the dominant group in each dot pattern. Perceptual grouping was not affected by tilting the frame. Based on a qualitative inspection, we remark that fundamental principles, for example, proximity, good continuation, and closure, respectively, in the order of strength, may remain the main drivers of the grouping behavior, irrespective of differences in the number of dots in each group, and the frame orientation. The numerosity condition did not affect our results. Similar trends were observed in patterns of 9 and 18 dots patterns.

The THINGS database is a freely available stimulus set that has the potential to facilitate the generation of theory that bridges multiple areas within cognitive neuroscience. The database consists of 26,107 high quality digital photos that are sorted into 1,854 concepts. While a valuable resource, relatively few technical details relevant to the design of studies in cognitive neuroscience have been described. We present an analysis of two key low-level properties of THINGS images, luminance and luminance contrast. These image statistics are known to influence common physiological and neural correlates of perceptual and cognitive processes. In general, we found that the distributions of luminance and contrast are in close agreement with the statistics of natural images reported previously. However, we found that image concepts are separable in their luminance and contrast: we show that luminance and contrast alone are sufficient to classify images into their concepts with above chance accuracy. We describe how these factors may confound studies using the THINGS images, and suggest simple controls that can be implemented a priori or post-hoc. We discuss the importance of using such natural images as stimuli in psychological research.

Monotonous and repetitive tasks cause vigilance, or sustained attention decrement, which possibly leads to irreparable accident consequences in the aerospace and nuclear industry. Buffering the decrement of vigilance in visual search tasks is essential for cognitive enhancement and ergonomic research. This study aimed to evaluate the efficacy of anodal transcranial direct current stimulation (tDCS) applied to the left frontal eye field (FEF) to improve the performance of the sustained visual search. Twenty-seven healthy participants received anodal and sham tDCS of 2 mA for 28.8 min and completed a visual search task lasting for approximately 40 min without any break. For the online effect, results showed that the d′ hit rate and accuracy under anodal tDCS were significantly higher than those under sham conditions during 0–19.2 min time intervals. For the after-effect, compared with sham, anodal tDCS caused significantly higher d′ in the 10 min after completing the tDCS. Our findings suggest that anodal tDCS over the left FEF could effectively mitigate the decline of visual vigilance performance by buffering cognitive resource depletion.

Ensemble coding and attention are two mechanisms utilized by our visual system to overcome the limitation of visual processing when confronted with the overwhelming visual information. Recent evidence in ensemble coding of size suggests that the attended items contributed more to the averaging. On the other hand, some new evidence also indicates that reduced attention jeopardies the perceptual averaging of stimuli. What is the relationship between attention and ensemble coding? To answer this question, in the current study, we tested whether an exogenous attentional cue would influence the reported mean emotion of a crowd. We showed participants a group of four faces with different emotions. Participants’ attention was guided to the happiest or saddest face (attention conditions), or not to any specific face (baseline condition). The results supported the notion that the attention alters the ensemble perception of the facial expression by elevating the weight of that face in the ensemble representation. This opens the question for the neural mechanisms of ensemble coding and its connection to visual attention.

Ambiguous figures (aka bistable, multistable, or reversible images) have fascinated scientists as well as laypersons for centuries. It may be surprising indeed how one and the same physical depiction can be experienced in perceptual awareness in cardinally different ways. In the most well-known examples of such illusions of multistability, the phenomenal change relates just to visual organization. Much less common are perceptions of alternating emotional content in the ambiguous visual image. Here, I introduce one such example.