Natural images dominate in binocular rivalry

Ecological approaches to perception have demonstrated that information encoding by the visual system is informed by the natural environment, both in terms of simple image attributes like luminance and contrast, and more complex relationships corresponding to Gestalt principles of perceptual organization. Here, we ask if this optimization biases perception of visual inputs that are perceptually bistable. Using the binocular rivalry paradigm, we designed stimuli that varied in either their spatiotemporal amplitude spectra or their phase spectra. We found that noise stimuli with “natural” amplitude spectra (i.e., amplitude content proportional to 1/f, where f is spatial or temporal frequency) dominate over those with any other systematic spectral slope, along both spatial and temporal dimensions. This could not be explained by perceived contrast measurements, and occurred even though all stimuli had equal energy. Calculating the effective contrast following attenuation by a model contrast sensitivity function suggested that the strong contrast dependency of rivalry provides the mechanism by which binocular vision is optimized for viewing natural images. We also compared rivalry between natural and phase-scrambled images and found a strong preference for natural phase spectra that could not be accounted for by observer biases in a control task. We propose that this phase specificity relates to contour information, and arises either from the activity of V1 complex cells, or from later visual areas, consistent with recent neuroimaging and single-cell work. Our findings demonstrate that human vision integrates information across space, time, and phase to select the input most likely to hold behavioral relevance.

Spatial coherence does not affect contrast discrimination for multiple Gabor stimuli

Gestalt grouping rules imply a process or mechanism for grouping together local features of an object into a perceptual whole. Several psychophysical experiments have been interpreted as evidence for constrained interactions between nearby spatial filter elements and this has led to the hypothesis that element linking might be mediated by these interactions. A common tacit assumption is that these interactions result in response modulation which disturbs a local contrast code. We addressed this possibility by performing contrast discrimination experiments using two-dimensional arrays of multiple Gabor patches arranged either (i) vertically, (ii) in circles (coherent conditions), or (iii) randomly (incoherent condition), as well as for a single Gabor patch. In each condition, contrast increments were applied to either the entire test stimulus (experiment 1) or a single patch whose position was cued (experiment 2). In experiment 3, the texture stimuli were reduced to a single contour by displaying only the central vertical strip. Performance was better for the multiple-patch conditions than for the single-patch condition, but whether the multiple-patch stimulus was coherent or not had no systematic effect on the results in any of the experiments. We conclude that constrained local interactions do not interfere with a local contrast code for our suprathreshold stimuli, suggesting that, in general, this is not the way in which element linking is achieved. The possibility that interactions are involved in enhancing the detectability of contour elements at threshold remains unchallenged by our experiments.

Squaring the circle: the cultural relativity of 'good' shape

The Gestalt theorists of the early twentieth century proposed a psychological primacy for circles, squares and triangles over other shapes. They described them as 'good' shapes and the Gestalt premise has been widely accepted. Rosch (1973), for example, suggested that shape categories formed around these 'natural' prototypes irrespective of the paucity of shape terms in a language. Rosch found that speakers of a language lacking terms for any geometric shape nevertheless learnt paired-associates to these 'good' shapes more easily than to asymmetric variants. We question these empirical data in the light of the accumulation of recent evidence in other perceptual domains that language affects categorization. A cross-cultural investigation sought to replicate Rosch's findings with the Himba of Northern Namibia who also have no terms in their language for the supposedly basic shapes of circle, square and triangle. A replication of Rosch (1973) found no advantage for these 'good' shapes in the organization of categories. It was concluded that there is no necessary salience for circles, squares and triangles. Indeed, we argue for the opposite because these shapes are rare in nature. The general absence of straight lines and symmetry in the perceptual environment should rather make circles, squares and triangles unusual and, therefore, less likely to be used as prototypes in categorization tasks. We place shape as one of the types of perceptual input (in philosophical terms, 'vague') that is readily susceptible to effects of language variation.

Utilising online shopping environment attributes holistically to create competitive advantage

As more consumers shop online, it becomes crucial for marketers to know how online shopping environments (OSEs) can be used to gain competitive advantage. This dissertation aims to explain theoretically how OSE attributes work together holistically to produce desirable consumer responses, applying and extending a theory from the environmental psychology literature to the online context. Firstly, the study conceptualises OSEs as virtual environments which may be perceived and experienced both cognitively and affectively through a technology-mediated interaction with a computer screen. A multi-disciplinary approach identifies key characteristics of OSEs: they involve consumers; they are more complex than their offline counterparts; they are likely first apprehended holistically; and they can elicit high levels of emotions and cognition. Secondly, the research uses a gestalt approach and extends Kaplan and Kalan’s (1982) Preference Framework, taking account of the specific characteristics of OSEs, which one visits specifically to obtain product information. The results support the proposition that OSEs are perceived in terms of their Sense-making and Exploratory attributes. Thirdly, the research explains how OSE attributes work together to produce desirable consumer responses. As hypothesised, Exploratory potential produces both Hedonic and Utilitarian value, and both kinds of value contribute to Site commitment. An unexpected result is that Sense-making potential does not produce Utilitarian value directly, but only through the mediation of Exploratory potential. The research contributes to marketing theory by: (1) identifying ways the internet has changed the nature of the shopping experience; (2) extending Kaplan and Kaplan’s Preference Framework to explain how consumers perceive OSEs holistically; (3) identifying the distinction between page-level and site-level perceptions, and (4) distinguishing between different sources of information (marketer vs. non-marketer). Managerially, the research provides a model for marketers to conceive and design retail websites whose attributes work together to create competitive advantage.

Perceiving conspecifics as integrated body-gestalts is an embodied process

We investigated the effect of posture congruence on social perception. Specifically, we tested the hypothesis that completing "body gestalts," rather than being a purely visual process, is mediated by congruence in the postures of observer and stimulus. We developed novel stimuli showing a face and 2 hands that could be combined in various ways to form "body gestalts" implying different postures. In 3 experiments we found that imitative finger movements were consistently faster when the observer's posture matched the posture implied by the configuration of face and hands shown onscreen, suggesting that participants intuitively used their own body schema to "fill in the gaps" in the stimuli. Besides shaping how humans perceive others' bodies, embodied body-gestalt (eBG) completion may be an essential social and survival mechanism, for example, allowing for quick recovery from deceptive actions. It may also partly explain why humans subconsciously align themselves in everyday interactions: This might facilitate optimal corepresentation at higher, conscious levels. © 2012 American Psychological Association.

Die unvermeidlichen Sonette: Thomas Mann und Shakespeare

Thomas Mann empfand zeitlebens eine große Bewunderung für Shakespeare, die sich in der für seine literarische Arbeitsweise typischen Form der intertextuellen Bezugnahme auf die Werke des englischen Klassikers offenbart. Diese literarische Beziehung lässt sich anhand deutlicher Allusionen von den Anfängen bis ins Spätwerk verfolgen und kulminiert im Doktor Faustus. Innerhalb der Shakespeare-Anspielungen in diesem Roman nehmen Bezüge zu den Sonetten eine zentrale Rolle ein. Über Jahrzehnte hinweg zeigte sich Thomas Mann fasziniert von diesen Gedichten und setzte sich vielfach mit der in ihnen dargestellten Verbindung von hetero- und homosexueller Anziehung sowie der zentralen Thematik künstlerischer Verewigung auseinander. Diese beiden Themenkreise stehen auch hier im Vordergrund und bilden eine Folie für Aspekte der Beziehung zwischen Leverkühn und Rudi Schwerdtfeger, wobei Thomas Mann nicht nur Motive aus den Gedichten aufgriff, sondern ebenfalls auf die Entstehungssituation der Sonette und ihre vermutete autobiographische Dimension Bezug nahm: Leverkühn - seinerseits ein Selbstporträt seines Autors - nimmt so zugleich die Rolle einer Shakespeareschen Figur und die Position des englischen Dichters selbst ein. Darüber hinaus ist sich Thomas Manns Protagonist dieser literarischen Beziehungen in hohem Grade bewusst und gestaltet sie selbst entscheidend mit. Wie keine andere Mannsche Gestalt vor ihm greift Leverkühn als Hauptfigur in die Handlung ein, manipuliert und inszeniert das Romangeschehen anhand literarischer Vorlagen. Dadurch erhält Thomas Manns komplexe Verwendung von Intertextualität eine zusätzliche Dimension und nimmt in diesem späten Roman geradezu postmoderne Züge an.