Geometric complexity and object search in infancy.

In four experiments we investigated the role of geometric path type in infants' ability to make spatial inferences about the location of a hidden object after they themselves had been moved through space. Nine-month-old infants were moved along geometrically simple paths of rotation (Experiments 1 and 2) or translation (Experiment 3) or along geometrically complex paths of combined rotation and translation (Experiment 4). In all but the fourth experiment, infants were able to retrieve an object hidden before they were moved, as long as the object was not located behind them at test time. Direct comparisons among the conditions showed that moving infants along geometrically simple paths led to significantly better performance than moving them along geometrically complex paths. We found the length of a path, the time needed to traverse it, and the likelihood of fixation of the target to be unrelated to the infants' performance. These findings are discussed in the context of theories of the development of spatial knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object permanence and working memory in cats (Felis catus).

Cats (Felis catus) find an object when it is visibly moved behind a succession of screens. However, when the object is moved behind a container and is invisibly transferred from the container to the back of a screen, cats try to find the object at or near the container rather than at the true hiding place. Four experiments were conducted to study search behavior and working memory in visible and invisible displacement tests of object permanence. Exp 1 compared performance in single and in double visible displacement trials. Exp 2 analyzed search behavior in invisible displacement tests and in analogs using a transparent container. Exps 3 and 4 tested predictions made from Exps 1 and 2 in a new situation of object permanence. Results showed that only the position changes that cats have directly perceived are encoded and activated in working memory because they are unable to represent or infer invisible movements. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prehension force as a measure of psychomotor skill for bare and gloved hands.

"The task consisted of a simple grasp, transport, and release of a cylindrical object into designated holes of a form-board. This object was instrumented with a pressure transducer permitting continuous recording of grasp force variations… . (a) handcoverings; (b) object weight; (c) distance moved; (d) direction of movement… . [were investigated in a factorial design with 6 Ss] handcoverings, weight, and distance exert a significant effect upon prehension force during a given task… this measurement seems to have potential value as an index of motor skills in that it is probably sensitive to changes in the amount of tactile sensory information available as well as to physical variables of the task." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Predictive action in infancy: tracking and reaching for moving objects

Because action plans must anticipate the states of the world which will be obtained when the actions take place, effective actions depend on predictions. The present experiments begin to explore the principles underlying early-developing predictions of object motion, by focusing on 6-month-old infants' head tracking and reaching for moving objects. Infants were presented with an object that moved into reaching space on four trajectories: two linear trajectories that intersected at the center of a display and two trajectories containing a sudden turn at the point of intersection. In two studies, infants' tracking and reaching provided evidence for an extrapolation of the object motion on linear paths, in accord with the principle of inertia. This tendency was remarkably resistant to counter-evidence, for it was observed even after repeated presentations of an object that violated the principle of inertia by spontaneously stopping and then moving in a new direction. In contrast to the present findings, infants fail to extrapolate linear object motion in preferential looking experiments, suggesting that early-developing knowledge of object motion, like mature knowledge, is embedded in multiple systems of representation.     

Oculocentric coding of inhibited eye movements to recently attended locations.

Results are reported for experiments that examined eye movements directed toward recently cued objects. In 1 experiment participants were slower to initiate saccades toward the earlier location of an object that had been cued, even though the cued object had subsequently moved away from that location. Other experiments involved exploring the reference frame within which the inhibited eye movements are encoded. These experiments revealed that the eye movement that is inhibited is encoded in an oculocentric—rather than an environmental—reference frame. However, simple detection as indexed by manual keypress responses is encoded in an environmental reference frame. The results have implications for inhibition of return, for the link between eye movements and attention, and for the nature of the spatial reference frames in which both covert and overt movements of attention are encoded. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Egocentric versus allocentric spatial coding in nine-month-old infants: Factors influencing the choice of code.

Presented 32 9-mo-old infants with a problem in which they saw an object hidden in 1 of 2 places but were prevented from searching for it until after the spatial relationship between infant and object had been changed in some way. Findings show the following: (a) Previous search experience at 1 place promoted response perseveration or egocentric spatial coding on later trials. (b) Infants were better at locating the object after they had moved than they were after the object had moved. (c) Differentiation of the covers for the 2 locations provided a more salient cue to allocentric position than differentiation of the surrounds of the 2 locations. The 2nd finding is taken as support for the hypothesis that as infants begin to crawl, they become better able to take into account their own displacements within a stable space but difficulties remain with the displacements of objects. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differences in the coding of spatial relations in face identification and basic-level object recognition.

The purpose of this investigation was to determine if the relations among the primitives used in face identification and in basic-level object recognition are represented using coordinate or categorical relations. In 2 experiments the authors used photographs of famous people's faces as stimuli in which each face had been altered to have either 1 of its eyes moved up from its normal position or both of its eyes moved up. Participants performed either a face identification task or a basic-level object recognition task with these stimuli. In the face identification task, 1-eye-moved faces were easier to recognize than 2-eyes-moved faces, whereas the basic-level object recognition task showed the opposite pattern of results. Results suggest that face identification involves a coordinate shape representation in which the precise locations of visual primitives are specified, whereas basic-level object recognition uses categorically coded relations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Energy-selective reconstructions in X-ray computerized tomography

All X-ray computerized tomography systems that are available or proposed base their reconstructions on measurements that integrate over energy. X-ray tubes produce a broad spectrum of photon energies and a great deal of information can be derived by measuring changes in the transmitted spectrum. We show that for any material, complete energy spectral information may be summarized by a few constants which are independent of energy. A technique is presented which uses simple, low-resolution, energy spectrum measurements and conventional computerized tomography techniques to calculate these constants at every point within a cross-section of an object. For comparable accuracy, patient dose is shown to be approximately the same as that produced by conventional systems. Possible uses of energy spectral information for diagnosis are presented.     

No-onset looming motion guides spatial attention.

These 6 experiments explored the ability of moving random dot patterns to attract attention, as measured by a simple probe-detection task. Each trial began with random motion (i.e., dots linearly moved in random directions). After 1 s motion in 1 hemifield became gradually coherent (i.e., all dots moved up-, down-, left-, or rightwards, or either towards or away from a vanishing point). The results show that only looming motion attracted attention, even when the task became a more demanding discrimination task. This effect is not due to an apparent magnification of stimuli presented in the focus of expansion. When the coherent motion started abruptly, all types of motion attracted attention at a short stimulus onset asynchrony. The looming motion effect only disappeared when attention was drawn to the target location by an arrow. These results suggest that looming motion plays a unique role in guiding spatial attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lexical access in aphasic and nonaphasic speakers.

An interactive 2-step theory of lexical retrieval was applied to the picture-naming error patterns of aphasic and nonaphasic speakers. The theory uses spreading activation in a lexical network to accomplish the mapping between the conceptual representation of an object and the phonological form of the word naming the object. A model developed from the theory was parameterized to fit normal error patterns. It was then "lesioned" by globally altering its connection weight, decay rates, or both to provide fits to the error patterns of 21 fluent aphasic patients. These fits were then used to derive predictions about the influence of syntactic categories on patient errors, the effect of phonology on semantic errors, error patterns after recovery, and patient performance on a single-word repetition task. The predictions were confirmed. It is argued that simple quantitative alterations to a normal processing model can explain much of the variety among patient patterns in naming. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unraveling mechanisms for expert object recognition: Bridging brain activity and behavior.

Behavioral sensitivity to object transformations and the response to novel objects (Greebles) in the fusiform face area (FFA) was measured several times during expertise training. Sensitivity to 3 transformations increased with expertise: (a) configural changes in which halves of objects were misaligned, (b) configural changes in which some of the object parts were moved, and (c) the substitution of an object part with a part from a different object. The authors found that holistic-configural effects can arise from object representations that are differentiated in terms of features or parts. Moreover, a holistic-inclusive effect was correlated with changes in the right FFA. Face recognition may not be unique in its reliance on holistic processing, measured in terms of both behavior and brain activation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gamma-aminobutyric acid: selective inhibition of electrically induced head-turning following intracaudate administration

GABA selectively antagonized head-turning elicited by electrical stimulation of the caudate nucleus in the rat when applied directly to the site of stimulation utilizing an electrode-cannula. Pretreatment with picrotoxin, a GABA antagonist, prevented the action of GABA on the head-turn response. This report provides in vivo evidence that GABA may play an inhibitory role in basal ganglia function. The findings are relevant to basal ganglia disorders in man.     

Object perception and object-directed reaching in infancy.

Conducted 5 experiments to investigate the effects of spatial and kinetic information on infants' perception of and reaching for objects. 65 20–23 wk old infants were presented with a small object, a larger object, and a background surface arranged in depth so that all were within reaching distance. Patterns of reaching for this display were observed, while spatial and kinetic properties of the display were varied. Results show that when the Ss reached for the display, they did not reach primarily for the surfaces that were nearer, smaller, or presented in motion. Ss reached, instead, for groups of surfaces that formed a unit that was spatially connected and/or that moved as a whole relative to its surroundings. Ss reached for the nearer of 2 objects as a distinct unit when the objects were separated in depth or when one object moved relative to the other. They reached for the 2 objects as a single unit when the objects were adjacent or when they moved together. The reaching patterns provide evidence that the Ss organized each display into the kind of units that adults call objects: manipulable units with internal coherence and external boundaries. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acetylcholine release from the frontal cortex during exploratory activity

The activation of the cortical cholinergic system was investigated in 3- and 25-month-old male Wistar rats, by measuring by transversal microdialysis the changes in cortical extracellular acetylcholine (ACh) levels during the performance of simple spontaneous tasks involving exploratory activity and working memory. Two days after implantation of the microdialysis probe in the frontal cortex, object recognition was investigated by either moving the rats from the home cage to the arena containing the objects or keeping the rats in the arena and introducing the objects. Spontaneous alternation was investigated in a Y runway. Young rats discriminated between familiar and novel objects and alternated in the Y runway, while aged rats were unable to discriminate. Whenever rats were moved from the home cage to the arena, ACh release increased (+70-80%) during the exploratory activity. Handling per se had no effect on extracellular ACh levels. When young rats were left in the arena, introduction of the objects caused some exploratory activity and object recognition but no increase in ACh release. ACh release increased by about 300% during spontaneous alternation. In aging rats basal extracellular ACh levels and their increase after placement in the arena were less than half that in young rats. Our work demonstrates that a novel environment activates the cortical cholinergic system, which presumably is associated with arousal mechanisms and selective attentional functions. It also demonstrates that in aging rats the cortical cholinergic hypofunction is associated with a loss of non-spatial working memory.     

The influence of enantiomorphic transformation on transsaccadic object integration.

Two experiments investigated whether the left–right orientation of an object is retained and integrated across a saccade during object identification. In Experiment 1, participants moved their eyes to the target object and named it as quickly as possible. In Experiment 2, participants looked through an array of 4 target objects in preparation for an immediate recognition test. In both experiments, a peripheral preview of the target object was presented before fixation. The preview stimulus was identical to the target object, the enantiomorph of the target object, or a control stimulus. Naming latencies were faster (Experiment 1) and gaze durations were shorter (Experiment 2) when the preview was identical to the target than when it was an enantiomorph of the target, suggesting that left–right orientation was retained and integrated across saccades. The results constrain models of transsaccadic integration and object identification. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Body- and environmental-stabilized processing of spatial knowledge.

In 5 experiments, the authors examined the perceptual and cognitive processes used to track the locations of objects during locomotion. Participants learned locations of 9 objects on the outer part of a turntable from a single viewpoint while standing in the middle of the turntable. They subsequently pointed to objects while facing the learning heading and a new heading, using imagined headings that corresponded to their current actual body heading and the other actual heading. Participants in 4 experiments were asked to imagine that the objects moved with them as they turned and were shown or only told that the objects would move with them; in Experiment 5, participants were shown that objects could move with them but were asked to ignore this as they turned. Results showed that participants tracked object locations as though the objects moved with them when shown but not when told about the consequences of their locomotion. Once activated, this processing mode could not be suppressed by instructions. Results indicated that people process object locations in a body- or an environment-stabilized manner during locomotion, depending on the perceptual consequences of locomotion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object perception in infancy: Interaction of spatial and kinetic information for object boundaries.

Infants' perception of object boundaries was studied using reaching and preferential looking methods. In 3 reaching studies, 5-month-old infants viewed 2 adjacent or separated objects that were stationary, moved together, or moved separately. Infants reached for the objects as distinct units when they moved separately or were separated in space and otherwise reached for the objects as 1 unit. In the looking study, 3-month-old infants were habituated to adjacent or separated objects alternately moving together and separately and were then tested with objects in the other spatial relationship. Patterns of dishabituation provided further evidence that separated or separately moving objects were perceived as distinct units. Infants appear to analyze surface arrangements and motions to form spatially connected bodies that move as wholes. This tendency may stem from an initial conception of the physical world. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object-based facilitation and inhibition from visual orienting in the human split-brain.

Object-based attention was examined in 2 split-brain patients. A precued object could move within a visual field or cross the midline to the opposite field. Normal individuals show an inhibition in detecting signals in the cued object whether it moves within or between fields. Both patients showed this effect when the cued object moved within a visual field. When it crossed the midline into the opposite visual field, however, detection was faster in the cued box. These results reveal both facilitatory and inhibitory effects on attention that are object based and may last for several hundred milliseconds. However, the inhibition requires an intact corpus callosum for interhemispheric transfer, whereas the facilitation is transferred subcortically. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Young children's use of syntactic cues to learn proper names and count nouns.

In 6 experiments, 144 toddlers were tested in groups ranging in mean age from 20 to 37 months. In all experiments, children learned a novel label for a doll or a stuffed animal. The label was modeled syntactically as either a count noun (e.g., "This is a ZAV") or a proper name (e.g., "This is ZAV"). The object was then moved to a new location in front of the child, and a second identical-looking object was placed nearby. The children's task was to choose 1 of the 2 objects as a referent for the novel word. By 24 months, both girls (Experiment 2) and boys (Experiment 5) were significantly more likely to select the labeled object if they heard a proper name than if they heard a count noun. At 20 months, neither girls (Experiments 1 and 6) nor boys (Experiment 1) demonstrated this effect. By their 2nd birthdays, children can use syntactic information to distinguish appropriately between labels for individual objects and those for object categories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)