Imagery in the congenitally blind: how visual are visual images?

Three experiments compared congenitally blind and sighted adults and children on tasks presumed to involve visual imagery in memory. In all three, the blind subjects' performances were remarkably similar to the sighted. The first two experiments examined Paivio's (1971) modality-specific imagery hypothesis. Experiment 1 used a paired-associate task with words whose referents were high in either visual or auditory imagery. The blind, like the sighted, recalled more high-visual-imagery pairs than any others. Experiment 2 used a free-recall task for words grouped according to modality-specific attributes, such as color and sound. The blind performed as well as the sighted on words grouped by color. In fact, the only consistent deficit in both experiments occurred for the sighted in recall of words whose referents are primarily auditory. These results challenge Paivio's theory and suggest either (a) that the visual imagery used by the sighted is no more facilitating than the abstract semantic representations used by the blind or (b) that the sighted are not using visual imagery. Experiment 3 used Neisser and Kerr's (1973) imaging task. Subjects formed images of scenes in which target objects were described as either visible in the picture plane or concealed by another object and thus not visible. On an incidental recall test for the target objects, the blind, like the sighted, recalled more pictorial than concealed targets. This finding suggests that the haptic images of the blind maintain occlusion just as the visual images of the sighted do.     

Artificial grammar learning in children: abstraction of rules or sensitivity to perceptual features?

We examined sensitivity to grammatical sequences of colors in an artificial grammar learning task in a sample of 120 children aged between 5 and 8 years. The aim of the experiment was to test whether the children would preferentially learn the specific salient features of the items they were exposed to or the rules that generated these items. The children were divided into two experimental groups (identical grammar but training items differing in their surface features) and a control group (random items). The results showed that regardless of age, participants learned the most frequent salient features of the items, as well as some kind of abstract relational information. However, the 8-year-olds presented a more complex result profile, with one of the experimental groups apparently developing sensitivity to grammatical rules. These results are discussed with reference to the main current models of implicit learning. Overall, the results provided more support for stimulus-specific processing models than for rule-based models.     

Perceptual learning for speech: Is there a return to normal?

Recent work on perceptual learning shows that listeners' phonemic representations dynamically adjust to reflect the speech they hear (Norris, McQueen, & Cutler, 2003). We investigate how the perceptual system makes such adjustments, and what (if anything) causes the representations to return to their pre-perceptual learning settings. Listeners are exposed to a speaker whose pronunciation of a particular sound (either /s/ or /integral/) is ambiguous (e.g., halfway between /s/ and /integral/). After exposure, participants are tested for perceptual learning on two continua that range from /s/ to /integral/, one in the Same voice they heard during exposure, and one in a Different voice. To assess how representations revert to their prior settings, half of Experiment 1's participants were tested immediately after exposure; the other half performed a 25-min silent intervening task. The perceptual learning effect was actually larger after such a delay, indicating that simply allowing time to pass does not cause learning to fade. The remaining experiments investigate different ways that the system might unlearn a person's pronunciations: listeners hear the Same or a Different speaker for 25 min with either: no relevant (i.e., 'good') /s/ or /integral/ input (Experiment 2), one of the relevant inputs (Experiment 3), or both relevant inputs (Experiment 4). The results support a view of phonemic representations as dynamic and flexible, and suggest that they interact with both higher- (e.g., lexical) and lower-level (e.g., acoustic) information in important ways.     

Is the binding of visual features in working memory resource-demanding?

The episodic buffer component of working memory is assumed to play a role in the binding of features into chunks. A series of experiments compared memory for arrays of colors or shapes with memory for bound combinations of these features. Demanding concurrent verbal tasks were used to investigate the role of general attentional processes, producing load effects that were no greater on memory for feature combinations than for the features themselves. However, the binding condition was significantly less accurate with sequential rather than simultaneous presentation, especially for items earlier in the sequence. The findings are interpreted as evidence of a relatively automatic but fragile visual feature binding mechanism in working memory. Implications for the concept of an episodic buffer are discussed.     

What is learning? On the nature and merits of a functional definition of learning

Learning has been defined functionally as changes in behavior that result from experience or mechanistically as changes in the organism that result from experience. Both types of definitions are problematic. We define learning as ontogenetic adaptation—that is, as changes in the behavior of an organism that result from regularities in the environment of the organism. This functional definition not only solves the problems of other definitions, but also has important advantages for cognitive learning research.     

Perceptual learning in the rat: stimulus differentiation or latent inhibition of common elements?

Preexposure to an unreinforced stimulus facilitates learning (perceptual learning) under some conditions, but it can have the opposite effect (latent inhibition) under other conditions. Researchers have suggested that perceptual learning depends on a change of context, whereas latent inhibition is usually context specific. The associative theory explains both phenomena within a single framework. The authors report 4 experiments that show that perceptual learning does not depend on a context change. The experiments suggest that latent inhibition, unlike perceptual learning, depends on passive exposure. Thus the results do not support the associative theory. They are more consistent with Gibson's stimulus-differentiation theory.     

Are visual features of a looming or receding object processed in a capacity-free manner?

Numerous experiments have examined whether moving stimuli capture spatial attention but none have sought to determine whether visual features of looming and receding objects are extracted in a capacity-free manner. The current experiment (N = 28) used the task-choice procedure originated by Besner and Care (2003) to examine this possibility. Stimuli were presented in 3D space by manipulating retinal disparity. Results indicate that features of an object are extracted in a capacity-free manner for both looming and receding objects for participants who consciously perceive motion but not for participants who do not consciously perceive motion. These results suggest that the cognitive system is biased to process potentially animate objects, perhaps because of the evolutionary advantage this cognitive ability may provide.     

Perceptual organization of line configurations: Is visual awareness necessary?

We examined whether configuring, which determines the appearance of grouped elements as a global shape, requires visual awareness, using a priming paradigm and two invisibility-inducing methods, CFS and sandwich masking. The primes were organized into configurations based on closure, collinearity, and symmetry (collinear primes), or on closure and symmetry (noncollinear primes). The prime-target congruency could be in configuration or in elements. During CFS, no significant response-priming was observed for invisible primes. When masking induced invisibility, a significant configuration response-priming was found for collinear and noncollinear primes, visible and invisible, with larger magnitude for the former. An element response-priming of equal magnitude was evident for visible and invisible noncollinear primes. Our results suggest that configuring can be accomplished in the absence of visual awareness when stimuli are rendered invisible by sandwich masking, but it benefits from visual awareness. Our results also suggest sensitivity to the available grouping cues in unconscious processing.     

Does prior knowledge facilitate the detection of visual targets in random noise?

The detectability of forms embedded within random visual noise has been found to be predictable from the autocorrelation transform of the stimulus pattern (Uttal, 1975). A basic assumption in the autocorrelation theory of form detection is that detectability is determined by the organization of the stimulus pattern, irrespective of the observer’s prior knowledge or expectations about the characteristics of the form. This assumption was tested by determining the effect of the size of the set of alternative target forms on performance of a forced-choice detection task. The targets were composed of dots in a straight line, appearing in one of a specified set of 2, 4, or 8 alternative positions in a pattern of randomly distributed masking dots. Detection accuracy was found to decrease as set size increased, but this decrease was close to what was predicted on the assumption that the random background was independently confusable with the target at each of the alternative positions. Thus, prior knowledge of the set of alternative targets appeared to have no effect on thevisual process, but only on thedecision process by virtue of the features that were relevant criteria for deciding which of the two patterns on each trial was most likely to contain the target. This result is consistent with the autocorrelation theory. This experiment may illustrate how the decision process has influenced the performance in many other experiments that have been assumed to demonstrate an effect of prior knowledge on perception.     

Proximal versus distal cue utilization in spatial navigation: the role of visual acuity?

Proximal versus distal cue use in the Morris water maze is a widely accepted strategy for the dissociation of various problems affecting spatial navigation in rats such as aging, head trauma, lesions, and pharmacological or hormonal agents. Of the limited number of ontogenetic rat studies conducted, the majority have approached the problem of preweanling spatial navigation through a similar proximal-distal dissociation. An implicit assumption among all of these studies has been that the animal's visual system is sufficient to permit robust spatial navigation. We challenged this assumption and have addressed the role of visual acuity in spatial navigation in the preweanling Fischer 344-N rat by training animals to locate a visible (proximal) or hidden (distal) platform using double or null extramaze cues within the testing environment. All pups demonstrated improved performance across training, but animals presented with a visible platform, regardless of extramaze cues, simultaneously reached asymptotic performance levels; animals presented with a hidden platform, dependent upon location of extramaze cues, differentially reached asymptotic performance levels. Probe trial performance, defined by quadrant time and platform crossings, revealed that distal-double-cue pups demonstrated spatial navigational ability superior to that of the remaining groups. These results suggest that a pup's ability to spatially navigate a hidden platform is dependent on not only its response repertoire and task parameters, but also its visual acuity, as determined by the extramaze cue location within the testing environment. The standard hidden versus visible platform dissociation may not be a satisfactory strategy for the control of potential sensory deficits.     

What is the role of the cerebellum in motor learning and cognition?

The exact role of the cerebellum in motor learning and cognition is controversial. Nonetheless, recent ideas and facts have prompted an attempt at building and testing a more unified and coherent conceptualization. This article will suggest that the cerebellum might indeed participate in both motor control and cognition, and in motor adaptation, motor learning, and procedural learning. The proposed process would entail stimulus-response linkage through trial and error learning, and would consist of groupings of single-response elements-motor and cognitive-into large combinations. After practice, the occurrence of a sensory or experiential `context' would automatically trigger the combined response. The parallel fiber is the proposed agent of stimulus-response linkage and of combining the response elements. The attempt here is to focus on the role of the parallel fiber as a possible combiner of downstream motor and cognitive elements.     

Units of visual individuation in rhesus macaques: objects or unbound features?

Vision begins with the processing of unbound visual features, which must eventually be bound together into object representations. Such feature binding is required for coherent visual perception, and accordingly has received a considerable amount of study in several domains. Neurophysiological work, often in monkeys, has revealed the details of how and where feature binding occurs in the brain, but methodological limitations have not allowed this research to elucidate just how feature binding operates spontaneously in real-world situations. In contrast, behavioral work with human infants has demonstrated how we use simpler unbound features to individuate and identify objects over time and occlusion in many types of events, but this work has not typically been able to isolate the role of feature binding in such processing. Here we provide a method for assessing the spontaneity and fidelity of feature binding in non-human primates, as this process is utilized in real-world situations, including simple foraging behaviors. Using both looking-time and manual-search measures in a natural environment, we show that free-ranging rhesus macaques (Macaca mulatta) spontaneously bind features in order to individuate objects across time and occlusion in dynamic events. This pattern of results demonstrates that feature binding is used in subtle ways to guide ecologically relevant behavior in a non-human animal, spontaneously and reliably, in its natural environment.     

When does visual attention select all features of a distractor?

What happens after visual attention is allocated to an object? Although many theories of attention assume that all of its features are selected and processed, there has been little direct evidence that an irrelevant feature dimension of an attended nontarget is processed. In 5 experiments presented here, the authors used a singleton paradigm to investigate the effect of attention on nontarget objects. Participants made a speeded feature discrimination of a target for which the response was either compatible or incompatible with an irrelevant feature dimension of a distractor. The results show that the irrelevant distractor features were processed to the point that they interfered with the response to the target. The response compatibility effect was observed even when the location of the target or the distractor was invariant, although it was much weaker when both locations were invariant. These results demonstrate that in many circumstances, an attended distractor is completely selected and fully processed, and the complete processing of distractors depends on a number of factors, many of which are related to the strength of attention to the distractor.     

Professional judgement in the assessment of risk: is there a role for systemic practice?

Risk assessment is an example of professional decision‐making pared to its stark essentials. Political pressures towards accountability and the need for defensible decisions encourage a ‘tick‐box’ approach to risk assessment, but this can create unrealistic expectations of certainty. In practice, as technological approaches produce ever more complex formal tools for assessing risk, their effectiveness remains dubious while our human decision‐making apparatus is marginalized. This article examines whether we should respect our ability to apprehend complex multi‐stranded narrative realities intuitively, with the hope that such intuitions might contribute to professional decision‐making. This idea is explored with reference to a case study.     

What matters in the associative learning of visual cues in foraging parasitoid wasps: colour or brightness?

Visual cues are known to be used by numerous animal taxa to gather information on quality and localisation of resources. Because environmental lighting can interfere with the spectral features of visual cues, the specific characteristics of the colour signals that promote forager decision and learning are still not known in the majority of insects (excepted in bees). We analysed the effect of previous experience on the use of visual information by the wasp Venturia canescens, a parasitoid of pyralidae, in the context of host searching. These parasitoids search for hosts concealed in several fruit species, so visual cues from the host microhabitat could play a key role in host finding. We also investigated the type of visual cues on which wasps based their decision. We tested whether wasps are able to associate an achromatic cue (brightness) or a chromatic one (hue, i.e. dominant wavelength and/or chroma) with the presence of hosts. Our results show that in the context of host foraging, chromatic cues are more reliable than brightness in achieving the associative learning process. Therefore, understanding the behavioural ecology of foraging should make use of the knowledge about the visual information used.     

Cognitive control: A role for implicit learning?

We investigated the influence of implicit learning on cognitive control. In a sequential Stroop task, participants implicitly learned a sequence placed on the color of the Stroop words. In Experiment 1, Stroop conflict was lower in sequenced than in random trials (learning-improved control). However, as these results were derived from an interaction between learning and conflict, they could also be explained by improved implicit learning (difference between random and sequenced trials), under incongruent compared with congruent trials (control-improved learning). Therefore, we further unraveled the direction of the interaction in 2 additional experiments. In Experiment 2, participants who learned the color sequence were no better at resolving conflict than participants who did not undergo sequence training. This shows that implicit knowledge does not directly reduce conflict (no learning-improved control). In Experiment 3, the amount of conflict did not directly improve learning either (no control-improved learning). However, conflict had a significant impact on the expression of implicit learning, as most knowledge was expressed under the highest amount of conflict. Thus, task-optimization was accomplished by an increased reliance on implicit sequence knowledge under high conflict. These findings demonstrate that implicit learning processes can be flexibly recruited to support cognitive control functions. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

Development of sensitivity to spacing versus feature changes in pictures of houses: Evidence for slow development of a general spacing detection mechanism?

Adults are expert at recognizing faces, in part because of exquisite sensitivity to the spacing of facial features. Children are poorer than adults at recognizing facial identity and less sensitive to spacing differences. Here we examined the specificity of the immaturity by comparing the ability of 8-year-olds, 14-year-olds, and adults to discriminate houses differing in the spacing between features versus those differing in the shape of the features themselves. By 8 years of age, children were more accurate for discriminations involving the feature set compared with the spacing set, and the difference in accuracy compared with adults was greater for the spacing set than for the feature set. Importantly, when sets were matched in difficulty for adults, this greater immaturity on the spacing set than on the feature set remained. The results suggest that, at least by age 8, immaturities in sensitivity to the spacing of features may be related to immaturities in general perceptual mechanisms rather than face-specific mechanisms.     

Revision: is visual perception a requisite for visual imagery?

Vision is the most highly developed sense in man and represents the doorway through which most of our knowledge of the external world arises. Visual imagery can be defined as the representation of perceptual information in the absence of visual input. Visual imagery has been shown to complement vision in this acquisition of knowledge--it is used in memory retrieval, problem solving, and the recognition of properties of objects. The processes underlying visual imagery have been assimilated to those of the visual system and are believed to share a neural substrate. However, results from studies in congenitally and cortically blind subjects have opposed this hypothesis. Here I review the currently available evidence.     

Is it dangerous? The role of an emotional visual search strategy and threat-relevant training in the detection of guns and knives

Counter-terrorism strategies rely on the assumption that it is possible to increase threat detection by providing explicit verbal instructions to orient people's attention to dangerous objects and hostile behaviours in their environment. Nevertheless, whether verbal cues can be used to enhance threat detection performance under laboratory conditions is currently unclear. In Experiment 1, student participants were required to detect a picture of a dangerous or neutral object embedded within a visual search display on the basis of an emotional strategy ‘is it dangerous?’ or a semantic strategy ‘is it an object?’. The results showed a threat superiority effect that was enhanced by the emotional visual search strategy. In Experiment 2, whilst trainee police officers displayed a greater threat superiority effect than student controls, both groups benefitted from performing the task under the emotional than semantic visual search strategy. Manipulating situational threat levels (high vs. low) in the experimental instructions had no effect on visual search performance. The current findings provide new support for the language-as-context hypothesis. They are also consistent with a dual-processing account of threat detection involving a verbally mediated route in working memory and the deployment of a visual template developed as a function of training.