Moving to higher ground: The dynamic field theory and the dynamics of visual cognition

In the present report, we describe a new dynamic field theory that captures the dynamics of visuo-spatial cognition. This theory grew out of the dynamic systems approach to motor control and development, and is grounded in neural principles. The initial application of dynamic field theory to issues in visuo-spatial cognition extended concepts of the motor approach to decision making in a sensori-motor context, and, more recently, to the dynamics of spatial cognition. Here we extend these concepts still further to address topics in visual cognition, including visual working memory for non-spatial object properties, the processes that underlie change detection, and the ‘binding problem’ in vision. In each case, we demonstrate that the general principles of the dynamic field approach can unify findings in the literature and generate novel predictions. We contend that the application of these concepts to visual cognition avoids the pitfalls of reductionist approaches in cognitive science, and points toward a formal integration of brains, bodies, and behavior.     

Implicit learning for probable changes in a visual change detection task

Previous research demonstrates that implicitly learned probability information can guide visual attention. We examined whether the probability of an object changing can be implicitly learned and then used to improve change detection performance. In a series of six experiments, participants completed 120–130 training change detection trials. In four of the experiments the object that changed color was the same shape (trained shape) on every trial. Participants were not explicitly aware of this change probability manipulation and change detection performance was not improved for the trained shape versus untrained shapes. In two of the experiments, the object that changed color was always in the same general location (trained location). Although participants were not explicitly aware of the change probability, implicit knowledge of it did improve change detection performance in the trained location. These results indicate that improved change detection performance through implicitly learned change probability occurs for location but not shape.     

Recognition of partly occluded objects by fish

The ability to visually complete partly occluded objects (so-called “amodal completion”) has been documented in mammals and birds. Here, we report the first evidence of such a perceptual ability in a fish species. Fish (Xenotoca eiseni) were trained to discriminate between a complete and an amputated disk. Thereafter, the fish performed test trials in which hexagonal polygons were either exactly juxtaposed or only placed close to the missing sectors of the disk in order to produce or not produce the impression (to a human observer) of an occlusion of the missing sectors of the disk by the polygon. In another experiment, fish were first trained to discriminate between hexagonal polygons that were either exactly juxtaposed or only placed close to the missing sectors of a disk, and then tested for choice between a complete and an amputated disk. In both experiments, fish behaved as if they were experiencing visual completion of the partly occluded stimuli. These findings suggest that the ability to visually complete partly occluded objects may be widespread among vertebrates, possibly inherited in mammals, birds and fish from early vertebrate ancestors.     

Discrimination of moving video images of self by pigeons (<Emphasis Type="Italic">Columba livia</Emphasis>)

The ability to recognize self has been known to be limited to some animal species, but previous research has focused almost exclusively on the animal's reaction to a mirror. Recent studies suggest that the temporal contingency between a subject's action and the corresponding visual scene reflected in a mirror plays an important role in self-recognition. To assess the roles of visual-proprioceptive contiguity in self-recognition, we explored whether pigeons are able to discriminate videos of themselves with various temporal properties. We trained five pigeons to respond to live video images of themselves (live self-movies) and not to video filmed during previous training sessions (pre-recorded self-movies). Pigeons learned to peck trial-unique live self-movies more frequently than pre-recorded self-movies. We conducted two generalization tests after pigeons learned to discriminate between the two conditions. First, discrimination acquired during training sessions was transferred to a test session involving live self-movies and new pre-recorded self-movies. Second, the same pigeons were tested in extinction procedure using delayed live self-movies and new pre-recorded self-movies. Although pigeons responded to delayed presentations of live self-movies more frequently than to new pre-recorded self-movies, the relative response rate to delayed presentation of live self-movies gradually decreased as the temporal discrepancy between pigeons' own behavior and the corresponding video increased. These results indicate that pigeons' discrimination of self-movies with various temporal properties was based on the temporal contiguity between their behavior and its visual feedback. The methodology used in the present experiment is an important step toward improving the experimental analysis of self-recognition in non-human animals.     

A neural model of how the brain computes heading from optic flow in realistic scenes

Visually-based navigation is a key competence during spatial cognition. Animals avoid obstacles and approach goals in novel cluttered environments using optic flow to compute heading with respect to the environment. Most navigation models try either explain data, or to demonstrate navigational competence in real-world environments without regard to behavioral and neural substrates. The current article develops a model that does both. The ViSTARS neural model describes interactions among neurons in the primate magnocellular pathway, including V1, MT⁺, and MSTd. Model outputs are quantitatively similar to human heading data in response to complex natural scenes. The model estimates heading to within 1.5° in random dot or photo-realistically rendered scenes, and within 3° in video streams from driving in real-world environments. Simulated rotations of less than 1°/s do not affect heading estimates, but faster simulated rotation rates do, as in humans. The model is part of a larger navigational system that identifies and tracks objects while navigating in cluttered environments.     

The Role of Native-Language Phonology in the Auditory Word Identification and Visual Word Recognition of Russian–English Bilinguals

Does native language phonology influence visual word processing in a second language? This question was investigated in two experiments with two groups of Russian-English bilinguals, differing in their English experience, and a monolingual English control group. Experiment 1 tested visual word recognition following semantic categorization of words containing four phonological vowel contrasts (\({/{{\rm i}}/-/{{\rm u}}/, /{{\rm I}}/-/\wedge/, /{{\rm i}}/-/{{\rm I}}/, /{{\varepsilon}}/-/\ae/}\)). Experiment 2 assessed auditory identification accuracy of words containing these four contrasts. Both bilingual groups demonstrated reduced accuracy in auditory identification of two English vowel contrasts absent in their native phonology (\(/{{\rm i}}/-/{{\rm I}}/, /{\varepsilon}/-/\ae/\)). For late- bilinguals, auditory identification difficulty was accompanied by poor visual word recognition for one difficult contrast (/i/-/I/). Bilinguals’ visual word recognition moderately correlated with their auditory identification of difficult contrasts. These results indicate that native language phonology can play a role in visual processing of second language words. However, this effect may be considerably constrained by orthographic systems of specific languages.     

Adolescents’ preferences for sexual dimorphism are influenced by relative exposure to male and female faces

Exposure to a particular population of faces can increase ratings of the normality and attractiveness of similar-looking faces. Such exposure can also refine the perceived boundaries of that face population, such that other faces are more readily perceived as dissimilar. We predicted that relatively less exposure to opposite-sex faces, as experienced by children at single-sex compared with mixed-sex schools, would decrease ratings of the attractiveness of sexual dimorphism in opposite-sex faces (that is, boys at single-sex schools would show a decreased preference for feminised faces, and girls at single-sex schools would show a decreased preference for masculinised faces). Consistent with this prediction, girls at single-sex compared with mixed-sex schools demonstrated significantly stronger preferences for facial femininity in both male and female faces. Boys at single-sex compared with mixed-sex schools demonstrated marginally stronger preferences for facial masculinity in male faces, but did not differ in their ratings of female faces. These effects were attenuated among some single-sex school pupils by the presence of adolescent opposite-sex siblings. These data add to the evidence that long-term exposure to a particular face population can influence judgements of other faces, and contribute to our understanding of the factors leading to individual differences in face preferences.     

The influence of perceptual and semantic categorization on inhibitory processing as measured by the N2–P3 response

In daily activities, humans must attend and respond to a range of important items and inhibit and not respond to unimportant distractions. Our current understanding of these processes is largely based on perceptually simple stimuli. This study investigates the interaction of conceptual-semantic categorization and inhibitory processing using Event Related Potentials (ERPs). Participants completed three Go–NoGo tasks that increased systematically in the degree of conceptual-semantic information necessary to respond correctly (from single items to categories of objects and animals). Findings indicate that the N2 response reflects inhibitory processing but does not change significantly with task difficulty. The P3 NoGo amplitude, on the other hand, is attenuated by task difficulty. Further, the latency of the peak of the P3 NoGo response elicited by the most difficult task is significantly later than are the peaks detected during performance of the other two tasks. Thus, the level of complexity of conceptual-semantic representations influences inhibitory processing in a systematic way. This inhibition paradigm may be a key for investigating inhibitory dysfunction in patient populations.     

Learning to attend: a connectionist model of situated language comprehension

Evidence from numerous studies using the visual world paradigm has revealed both that spoken language can rapidly guide attention in a related visual scene and that scene information can immediately influence comprehension processes. These findings motivated the coordinated interplay account ( Knoeferle & Crocker, 2006 ) of situated comprehension, which claims that utterance-mediated attention crucially underlies this closely coordinated interaction of language and scene processing. We present a recurrent sigma-pi neural network that models the rapid use of scene information, exploiting an utterance-mediated attentional mechanism that directly instantiates the CIA. The model is shown to achieve high levels of performance (both with and without scene contexts), while also exhibiting hallmark behaviors of situated comprehension, such as incremental processing, anticipation of appropriate role fillers, as well as the immediate use, and priority, of depicted event information through the coordinated use of utterance-mediated attention to the scene.