Witt - Introducting Hat Graphs

Visualizing data through graphs can be an effective way to communicate one’s results. A ubiquitous graph and common technique to communicate behavioral data is the bar graph. The bar graph was first invented in 1786 and little has changed in its format. Here, a replacement for the bar graph is proposed. The new format, called a hat graph, maintains some of the critical features of the bar graph such as its discrete elements, but eliminates redundancies that are problematic when the baseline is not at 0. Hat graphs also include elements designed to improve Gestalt grouping principles and engage object-based attention. The effectiveness of the hat graph was tested in two empirical studies for which participants had to find and identify the condition that lead to the biggest improvement from baseline to final test. Performance with hat graphs was 30 - 40% faster than with bar graphs.

The Place of White in a World of Grays: A Double Anchoring Theory of Lightness Perception

The specific gray shades in a visual scene can be derived from relative luminance values only when an anchoring rule is followed. The double-anchoring theory I propose in this article, as a development of the anchoring theory of Gilchrist et al. (1999), assumes that any given region (a) belongs to one or more frameworks, created by Gestalt grouping principles, and (b) is independently anchored, within each framework, to both the highest luminance and the surround luminance. The region's final lightness is a weighted average of the values computed, relative to both anchors, in all frameworks. The new model accounts not only for all lightness illusions that are qualitatively explained by the anchoring theory but also for a number of additional effects, and it does so quantitatively, with the support of mathematical simulations.

Hidden Images

It is relatively easy to hide pictorial images, but this is of little value if they remain hidden. Presenting hidden images for visual purposes is a modern preoccupation, and some of the perceptual processes involved in them are described in this chapter. Pictorial images can be concealed in terms of detection or recognition. In both cases there is interplay between the global features of the concealed image and the local elements that carry it. Gestalt grouping principles can hinder as well as help recognition. Examples of images (mostly faces) hidden in geometrical designs and text as well as orientation are shown. Rather than being pictorial puzzles alone, hidden images can reveal aspects of visual processing. This chapter explores these concepts and related ideas such as perceptual portraits and pictorial puzzles.

Come Together, Right Now: Dynamic Overwriting of an Object's History through Common Fate

The objects around us constantly move and interact, and the perceptual system needs to monitor on-line these interactions and to update the object's status accordingly. Gestalt grouping principles, such as proximity and common fate, play a fundamental role in how we perceive and group these objects. Here, we investigated situations in which the initial object representation as a separate item was updated by a subsequent Gestalt grouping cue (i.e., proximity or common fate). We used a version of the color change detection paradigm, in which the objects started to move separately, then met and stayed stationary, or moved separately, met, and then continued to move together. We monitored the object representations on-line using the contralateral delay activity (CDA; an ERP component indicative of the number of maintained objects), during their movement, and after the objects disappeared and became working memory representations. The results demonstrated that the objects' representations (as indicated by the CDA amplitude) persisted as being separate, even after a Gestalt proximity cue (when the objects “met” and remained stationary on the same position). Only a strong common fate Gestalt cue (when the objects not just met but also moved together) was able to override the objects' initial separate status, creating an integrated representation. These results challenge the view that Gestalt principles cause reflexive grouping. Instead, the object initial representation plays an important role that can override even powerful grouping cues.