Does low perceptual load enable capture by colour singletons?

There is considerable debate as to whether colour singletons can capture attention in a stimulus-driven manner. In this study, we explore one potential capture enabling condition—low perceptual load. To test this hypothesis, we manipulated perceptual load in a flanker task in which flanking letters sometimes were colour singletons. If low load enhances capture by colour singletons, then colour singletons should produce an especially large increase in overall reaction times and in flanker–target compatibility effects. Neither of these predictions was confirmed in any of the four experiments reported here, although we did replicate the classic load effects from previous studies. These experiments indicate that although perceptual load does strongly modulate overall performance, it does not facilitate capture by colour singletons. This finding contrasts sharply with findings from other types of salient stimuli (abrupt onsets and moving objects). Implications for theories of attentional capture will be discussed.     

Subjectivity and unconsciousness

Concepts of the unconscious were crucial to both Jung's and Freud's thinking. Psychoanalytic and analytical psychological views of the unconscious are compared and contrasted, and both are critically reviewed. It is suggested that we need to revise our conceptualization so as to take better account of the role of the analyst's expectations and inferences, and therefore of his or her subjectivity, whenever he or she makes a clinical judgement that unconscious mental processes are in operation. Some technical implications of a revised definition of unconsciousness are considered, especially indications for self-disclosure by an analyst of his or her own experience of events within the treatment.     

Extending the classical view of representation

Representation has always been a central part of models in cognitive science, but this idea has come under attack. Researchers advocating the alternative approaches of perceptual symbol systems, situated action, embodied cognition, and dynamical systems have argued against central assumptions of the classical representational approach to mind. We review the core assumptions of the representational view and these four suggested alternatives. We argue that representation should remain a core part of cognitive science, but that the insights from these alternative approaches must be incorporated into models of cognitive processing.     

Phonological abstraction in the mental lexicon

A perceptual learning experiment provides evidence that the mental lexicon cannot consist solely of detailed acoustic traces of recognition episodes. In a training lexical decision phase, listeners heard an ambiguous [f–s] fricative sound, replacing either [f] or [s] in words. In a test phase, listeners then made lexical decisions to visual targets following auditory primes. Critical materials were minimal pairs that could be a word with either [f] or [s] (cf. English knife–nice), none of which had been heard in training. Listeners interpreted the minimal pair words differently in the second phase according to the training received in the first phase. Therefore, lexically mediated retuning of phoneme perception not only influences categorical decisions about fricatives (Norris, McQueen, & Cutler, 2003), but also benefits recognition of words outside the training set. The observed generalization across words suggests that this retuning occurs prelexically. Therefore, lexical processing involves sublexical phonological abstraction, not only accumulation of acoustic episodes.     

Infants chunk object arrays into sets of individuals

Research suggests that, using representations from object-based attention, infants can represent only 3 individuals at a time. For example, infants successfully represent 1, 2, or 3 hidden objects, but fail with 4 (Developmental Science 6 (2003) 568), and a similar limit is seen in adults' tracking of multiple objects (see Cognitive Psychology 38 (1999) 259). In the present experiments we used a manual search procedure to ask whether infants can overcome this limit of 3 by chunking individuals into sets. Experiments 1 and 2 replicate infants' failure to represent a total of 4 objects. We then show that infants can exceed this limit when items are spatiotemporally grouped into two sets of 2 prior to hiding, leading infants to successfully represent a total of 4 objects. Experiment 3 demonstrates that infants tracked the 4 objects as two sets of 2, searching for each set in its correct hiding location. That infants represented the number of individuals in each set is demonstrated by their reaching for the correct number of objects in each location. These results suggest that by binding individuals into sets, infants can increase their representational capacity. This is the first evidence for chunking abilities in infants.     

On aims and methods in the neuroimaging of derived relations

Ingenious and seemingly powerful technologies have been developed recently that enable the visualization in some detail of events in the brain concomitant upon the ongoing behavioral performance of a human participant. Measurement of such brain events offers at the very least a new set of dependent variables in relation to which the independent variables familiarly manipulated in the operant laboratory may be explored. Two related paradigms in which a start has been made in such research concern the derivation of novel or emergent relations from a baseline set of trained relations, and include the phenomenon of transitive inference (TI), observed in studies of stimulus equivalence (SE) and serial learning (SL) or seriation. This paper reviews some published and forthcoming neuroimaging studies of these and related phenomena, and considers how this line of research both demands and represents a welcome synthesis between types of question and levels of explanation in behavioral science that often have been seen as antithetical.     

Color term knowledge does not affect categorical perception of color in toddlers

Categorical perception of color is shown when colors from the same category are discriminated less easily than equivalently spaced colors that cross a category boundary. The current experiments tested various models of categorical perception. Experiment 1 tested for categorical responding in 2- to 4-year-olds, the age range for the onset establishment of color term knowledge. Experiment 2 tested for categorical responding in Himba toddlers, whose language segments the color space differently from the way in which the English language does so. Experiment 3 manipulated the conditions of the task to explore whether the categorical responding in Experiments 1 and 2 was equivalent to categorical perception. Categorical perception was shown irrespective of naming and was not stronger in those children with more developed color term knowledge. Cross-cultural differences in the extent of categorical perception were not found. These findings support universalistic models of color categorization and suggest that color term knowledge does not modify categorical perception, at least during the early stages of childhood.     

Serial order processing in human infants and the role of multisensory redundancy

Perception, production, and understanding of sequences is fundamental to human behavior and depends, in large part, on the ability to detect serial order. Despite the importance of this issue across many domains of human functioning, the development of serial order skills has been neglected in developmental studies. The current article reviews evidence that the basic temporal and spatiotemporal skills that are necessary for the development of serial order skills emerge early in human development. The article then presents recent evidence from the authors laboratory showing that serial order perceptual skills emerge at the same time and improve rapidly. Consistent with a multisensory redundancy view of perception, when serial order perceptual abilities first emerge in infancy, they depend critically on the redundant specification of sequences in both the auditory and visual modalities. The findings suggest that infants ability to perceive the surface serial order characteristics of sequentially organized events provides the necessary antecedents to the development of more complex serial order skills that ultimately enable us to extract meanings from sequentially organized events and perform complex sequential actions.Edited by: Marie-Hélène Giard and Mark Wallace     

Acquiring new spatial intuitions: learning to reason about rotations

There are certain simple rotations of objects that most people cannot reason about accurately. Reliable gaps in the understanding of a fundamental physical domain raise the question of how learning to reason in that domain might proceed. Using virtual reality techniques, this project investigated the nature of learning to reason across the domain of simple rotations. Learning consisted of the acquisition of spatial intuitions: there was encoding of useful spatiotemporal information in specific problem types and a gradual accumulation of this understanding across the domain. This pattern of learning through the accumulation of intuitions is especially interesting for rotational motion, in which an elegant domain-wide kinematics is available to support insightful learning. Individual ability to reason about rotations correlated highly with mastery motivation, skill in fluid reasoning, and skill in reasoning about spatial transformations. Thus, general cognitive advantages aided the understanding of individual rotations without guaranteeing immediate generalization across the domain.     

How owls structure visual information

Recent studies on perceptual organization in humans claim that the ability to represent a visual scene as a set of coherent surfaces is of central importance for visual cognition. We examined whether this surface representation hypothesis generalizes to a non-mammalian species, the barn owl (Tyto alba). Discrimination transfer combined with random-dot stimuli provided the appropriate means for a series of two behavioural experiments with the specific aims of (1) obtaining psychophysical measurements of figure–ground segmentation in the owl, and (2) determining the nature of the information involved. In experiment 1, two owls were trained to indicate the presence or absence of a central planar surface (figure) among a larger region of random dots (ground) based on differences in texture. Without additional training, the owls could make the same discrimination when figure and ground had reversed luminance, or were camouflaged by the use of uniformly textured random-dot stereograms. In the latter case, the figure stands out in depth from the ground when positional differences of the figure in two retinal images are combined (binocular disparity). In experiment 2, two new owls were trained to distinguish three-dimensional objects from holes using random-dot kinematograms. These birds could make the same discrimination when information on surface segmentation was unexpectedly switched from relative motion to half-occlusion. In the latter case, stereograms were used that provide the impression of stratified surfaces to humans by giving unpairable image features to the eyes. The ability to use image features such as texture, binocular disparity, relative motion, and half-occlusion interchangeably to determine figure–ground relationships suggests that in owls, as in humans, the structuring of the visual scene critically depends on how indirect image information (depth order, occlusion contours) is allocated between different surfaces. Electronic Publication