Effect of auditory numerical information on infants' looking behavior: Contradictory evidence.

Seven-month-old infants saw pairs of slides of two and three objects while listening to either two or three drum beats. Subjects looked longer at the noncorresponding display, particularly during the second block of 16 trials. These results are not in accord with those of Starkey, Spelke, and Gelman (1983). Although 7-month-old infants' attentiveness to a visually presented numerical event might be influenced by auditory information, the data call into question the suggestion that this influence is mediated by crossmodal matching of numerical information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial determinants in the perception of self-produced leg movements in 3- to 5-month-old infants.

Sixty 3- and 4-5-month-old infants were simultaneously presented with 2 on-line video images of their own legs. In 3 experiments, the temporal contingency between the 2 images and the infant's actual movements was maintained constant while their spatial relationships were systematically manipulated. In Experiment 1, both spatial orientation and directionality of movement on the visual display were varied. In Experiment 2, only directionality of movement was varied. In Experiment 3, only spatial orientation was varied. Analyses focused on infants' preferential looking and relative amount of leg activity while looking at either view. Results show that both groups of infants actively compared and explored the 2 views of their legs. They looked significantly longer and generated significantly more leg activity while looking at the view displaying a left-right inversion. These results demonstrate that the perception of self-produced leg movements by young infants is partially determined by spatial information about movement directionality. The results are interpreted as evidence of an early detection of intermodal invariants which specify the body as a situated agent in the environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensory dominance in infants: I. Six-month-old infants' response to auditory-visual compounds.

To investigate sensory dominance in early development, a series of studies was conducted to examine 6-month-old infants' processing of multisensory stimulus compounds. The infants were first habituated with a compound stimulus consisting of a flashing checkerboard and a pulsing sound. To assess attention to aspects of the compound stimulus, the infants received separate test trials where compounds differed in the rate and/or duration at which the visual, the auditory, or both components were presented. One consistent finding was that the infants discriminated changes in the temporal characteristics of the auditory component but not in the visual component. Their responsiveness to the auditory information depended on the number of discriminative cues available during either the habituation or the test phases and on the temporal distinctiveness of the auditory and visual components during the habituation phase. This consistent failure to respond to changes in the visual component led to the conclusion that auditory dominance was operating. This conclusion was reinforced by the finding that the infants failed to discriminate a change in the rate of the visual component even when the intensity of the visual component was increased relative to that of the auditory component, and by the finding that the infants could discriminate temporal changes in the visual component following habituation with just the visual component. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Set size, novelty, and visual pop-out in infancy.

The effects of set size and novelty on visual pop-out in 6-month-old infants was assessed in a perceptual-identification (memory reactivation) paradigm in which infants, trained and tested in their own homes, viewed a mobile containing a unique novel or familiar object amidst different numbers of familiar or novel distractors, respectively. Unique objects of both types popped out at all set sizes except the largest, where there was modest evidence that familiar distractors speeded processing (Experiment 1). When the proportion of familiar targets in a display of intermediate set size was increased, however, infants no longer detected the familiar target (Experiment 2). These findings offer additional support for the proposition that visual pop-out in infants and adults is the same phenomenon. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The drawbridge phenomenon: Representational reasoning or perceptual preference?

Two experiments investigated whether infants would look longer at a rotating "drawbridge" that appeared to violate physical laws because they knew that it was causally impossible, as claimed by R. Baillargeon, E. S. Spelke, and S. Wasserman (1985) and R. Baillargeon (1987a). Using a habituation paradigm, they reported that infants looked longer at a display that appeared impossible (rotated 190° while an obstructing box was behind it) than at one that appeared possible (rotated only 112°, appearing to stop at the box). Experiment 1 eliminated habituation to 180° screen rotations. Still, infants looked longer at the 180° impossible rotations. Critically, however, infants also looked longer at possible 180° rotations in Experiment 2, in which no obstruction was present. Moreover, no difference in effect size was found between the 2 experiments. These findings indicate that infants' longer looking at 180° rotations is due to simple perceptual preference for more motion. They question R. Baillargeon's (1987a) claim that it is due to infants' representational reasoning about physically impossible object permanence events. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is dual-task slowing instruction dependent?

When 2 tasks must be performed concurrently, each requiring a choice of response, dual-task slowing is typically found. However, E. H. Schumacher et al. (1997) reported that dual-task slowing can be eliminated when equal priority is assigned to each task. Experiment 1 largely confirmed this with the same tasks as Schumacher et al. (tasks using stimulus–response combinations of visual–manual and auditory–vocal pairings). Experiment 2 retained the equal-priority instructions but switched the task pairings (to visual–vocal and auditory–manual); substantial dual-task slowing occurred. Experiment 3 used the same two response sets but only a single stimulus; slowing was again obtained despite equal priority instructions. Equalizing task priority was not sufficient to eliminate interference; relatively unusual cases in which dual-task interference is eliminated seem to depend on task-specific features. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stop-reaction time and the internal clock

In a stop-reaction-time (stop-RT) task, a subject is presented with a regular, isochronous sequence of brief signals separated by a constant time interval, or stimulus onset asynchrony (SOA). His/her task is to press a response key as fast as possible when the sequence stops. As the sequence unfolds, an internal representation of the SOA duration builds up. Stop-RT is assumed to be triggered when an internal clock, operating as an "alarm clock," reaches a time criterion. Criterion setting is contingent upon variability in the SOA's internal representation. In Experiment 1A, stop-RT was measured for isochronous sequences of brief tones, light flashes, and also sequences of tones and flashes presented in regular alternation (tone-light-tone ...). Stop-RT was a linear function of SOA duration (ranging from 250 to 1,000 msec), regardless of modality, supporting a "central-clock" hypothesis. On the other and, taken together, the results of Experiments 1A, 1B, 2, and 3 suggest that no internal representation of the bimodal (tone-light) SOA of alternating sequences builds up. Indeed, an alternating sequence is physically equivalent to two interlaced isochronous subsequences, one auditory and one visual. So, two internal representations, one for the auditory (tone-tone) and one for the visual (light-light) SOA, could build up, and two time criteria running "in parallel" could thus support stop-RT. To provide a critical test of parallel timing, stop-RT was measured for bimodal 5:3 polyrhythms formed by the superposition of auditory and visual isochronous sequences that had different SOA durations (Experiment 4). Parallel timing accounted for a large proportion of variance in polyrhythmic stop-RT data. Overall findings can be accounted for by assuming a functional architecture of an internal clock in which pulses emitted by a central pacemaker are available in parallel with two modality-specific switch-accumulator "timing modules."     

Detection of the traversability of surfaces by crawling and walking infants.

In four studies we investigated the perception of the affordance for traversal of a supporting surface. The surface presented was either rigid or deformable, and this property was specified either optically, haptically, or both. In Experiment 1A, crawling and walking infants were presented with two surfaces in succession: a standard surface that both looked and felt rigid and a deforming surface that both looked and felt nonrigid. Latency to initiate locomotion, duration of visual and haptic exploration, and displacement activity were coded from videotapes. Compared with the standard, the deforming surface elicited longer latency, more exploratory behavior, and more displacement in walkers, but not in crawlers, suggesting that typical mode of locomotion influences perceived traversability. These findings were replicated in Experiment 1B, in which the infant was presented with a dual walkway, forcing a choice between the two surfaces. Experiments 2, 3A and B, and 4A and B investigated the use of optical and haptic information in detecting traversability of rigid and nonrigid surfaces. Patterns of exploration varied with the information presented and differed for crawlers and walkers in the case of a deformable surface, as an affordance theory would predict. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' ability to parse continuous actions.

In a series of 3 experiments, the authors examined 6- and 8-month-old infants' capacities to detect target actions in a continuous action sequence. In Experiment 1, infants were habituated to 2 different target actions and subsequently were presented with 2 continuous action sequences that either included or did not include the familiar target actions. Infants looked significantly longer at the sequences that were novel. Experiment 2 presented the habituation and test trials in the reverse order. The results showed that infants habituated to the sequence still showed reliable evidence of recognizing the target action during the test trials. Experiment 3 was comparable to Experiment 2, except it tested whether infants could detect a different event segment, namely the transitions between events. The results showed that infants did not discriminate between test trials suggesting that transitions between events are not as easy for infants to recognize. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rhesus monkeys (Macaca mulatta) enumerate large and small sequentially presented sets of items using analog numerical representations.

Two rhesus monkeys selected the larger of two sequentially presented sets of items on a computer monitor. In Experiment 1, performance was related to the ratio of set sizes, and the monkeys discriminated between sets with up to 10 items. Performance was not disrupted when 1 set had fewer than 4 items and 1 set had more than 4 items, a critical trial type for differentiating object file and analog models of numerical representation. Experiment 2 controlled the interitem rate of presentation. Experiment 3 included some trials on which number and amount (visual surface area) offered conflicting cues. Experiment 4 varied the total duration of set presentation and the duration of item visibility. In all of the experiments, performance remained high, although total set presentation duration also acted as a partial cue for the monkeys. Overall, the data indicated that rhesus monkeys estimate the approximate number of items in sequentially presented sets and that they are not relying solely on nonnumerical cues such as rate, duration, or cumulative amount. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object segregation in 8-month-old infants

Two experiments examined 8-month-old infants' use of configural and physical knowledge in segregating three-dimensional adjacent displays. The infants in Experiment I saw two identical yellow octagons standing side by side: in the test events, a hand grasped the right octagon and pulled it to the side. The infants looked reliably longer when the octagons moved apart than when they moved together, suggesting that the infants (a) perceived the octagons as a single unit and hence (b) expected them to move together and were surprised when they did not. The infants in Experiment 2 saw a yellow cylinder and a blue box: a hand grasped the cylinder and pulled it to the side. The infants looked reliably longer when the box moved with the cylinder than when the box remained in place, suggesting that they (a) viewed the cylinder and box as distinct units and thus (b) expected the cylinder to move alone and were surprised when it did not. These results indicate that, by 8 months of age, infants use configural knowledge when organizing adjacent displays: they expect similar parts to belong to the same unit and dissimilar parts to belong to distinct units. Additional results revealed that 8-month-old infants' interpretation of displays is affected not only by configural but also by physical consideration. Thus, infants in Experiment 1 who saw a thin blade lowered between the octagons viewed them as two rather than as one unit. Similarly, infants in Experiment 2 who saw the cylinder lying above instead of on the apparatus floor perceived the cylinder and box as one rather than two units. These results indicate that 8-month-old infants bring to bear their knowledge of impenetrability and support when parsing adjacent displays. Furthermore, when faced with two conflicting interpretations of a display, one suggested by their configural and one by their physical knowledge, infants allow the latter to supersede the former. Together, these findings suggest that, by 8 months of age infants approach to segregation is fundamentally similar to that of adults.     

Infants learn about objects from statistics and people.

In laboratory experiments, infants are sensitive to patterns of visual features that co-occur (e.g., Fiser & Aslin, 2002). Once infants learn the statistical regularities, however, what do they do with that knowledge? Moreover, which patterns do infants learn in the cluttered world outside of the laboratory? Across 4 experiments, we show that 9-month-olds use this sensitivity to make inferences about object properties. In Experiment 1, 9-month-old infants expected co-occurring visual features to remain fused (i.e., infants looked longer when co-occurring features split apart than when they stayed together). Forming such expectations can help identify integral object parts for object individuation, recognition, and categorization. In Experiment 2, we increased the task difficulty by presenting the test stimuli simultaneously with a different spatial layout from the familiarization trials to provide a more ecologically valid condition. Infants did not make similar inferences in this more distracting test condition. However, Experiment 3 showed that a social cue did allow inferences in this more difficult test condition, and Experiment 4 showed that social cues helped infants choose patterns among distractor patterns during learning as well as during test. These findings suggest that infants can use feature co-occurrence to learn about objects and that social cues shape such foundational learning in distraction-filled environments. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Differential effects of auditory and visual signals on clock speed and temporal memory.

The effects of signal modality on duration classification in college students were studied with the duration bisection task. When auditory and visual signals were presented in the same test session and shared common anchor durations, visual signals were classified as shorter than equivalent duration auditory signals. This occurred when auditory and visual signals were presented sequentially in the same test session and when presented simultaneously but asynchronously. Presentation of a single modality signal within a test session, or both modalities but with different anchor durations did not result in classification differences. The authors posit a model in which auditory and visual signals drive an internal clock at different rates. The clock rate difference is due to an attentional effect on the mode switch and is revealed only when the memories for the short and long anchor durations consist of a mix of contributions from accumulations generated by both the fast auditory and slower visual clock rates. When this occurs auditory signals seem longer than visual signals relative to the composite memory representation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Compatibility of motion facilitates visuomotor synchronization.

Prior research indicates that synchronized tapping performance is very poor with flashing visual stimuli compared with auditory stimuli. Three finger-tapping experiments compared flashing visual metronomes with visual metronomes containing a spatial component, either compatible, incompatible, or orthogonal to the tapping action. In Experiment 1, synchronization success rates increased dramatically for spatiotemporal sequences of both geometric and biological forms over flashing sequences. In Experiment 2, synchronization performance was best when target sequences and movements were directionally compatible (i.e., simultaneously down), followed by orthogonal stimuli, and was poorest for incompatible moving stimuli and flashing stimuli. In Experiment 3, synchronization performance was best with auditory sequences, followed by compatible moving stimuli, and was worst for flashing and fading stimuli. Results indicate that visuomotor synchronization improves dramatically with compatible spatial information. However, an auditory advantage in sensorimotor synchronization persists. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Directed attention prolongs the perceived duration of a brief stimulus

Stelmach, Herdman, and McNeil (1994) suggested recently that the perceived duration for attended stimuli is shorter than that for unattended ones. In contrast, the attenuation hypothesis (Thomas & Weaver, 1975) suggests the reverse relation between directed attention and perceived duration. We conducted six experiments to test the validity of the two contradictory hypotheses. In all the experiments, attention was directed to one of two possible stimulus sources. Experiments 1 and 2 employed stimulus durations from 70 to 270 msec. A stimulus appeared in either the visual or the auditory modality. Stimuli in the attended modality were rated as longer than stimuli in the unattended modality. Experiment 3 replicated this finding using a different psychophysical procedure. Experiments 4-6 showed that the finding applies not only to stimuli from different sensory modalities but also to stimuli appearing at different locations within the visual field. The results of all six experiments support the assumption that directed attention prolongs the perceived duration of a stimulus.     

Infants' understanding of the link between visual perception and emotion: "If she can't see me doing it, she won't get angry."

Two experiments investigated 18-month-olds' understanding of the link between visual perception and emotion. Infants watched an adult perform actions on objects. An emoter then expressed neutral affect or anger toward the adult in response to the adult's actions. Subsequently, infants were given 20 s to interact with each object. In Experiment 1, the emoter faced infants with a neutral expression during each 20-s response period but looked at either a magazine or the infant. In Experiment 2, the emoter faced infants with a neutral expression, and her eyes were either open or closed. When the emoter visually monitored infants' actions, the infants regulated their object-directed behavior on the basis of their memory of the emoter's affect. However, if the previously angry emoter read a magazine (Experiment 1) or closed her eyes (Experiment 2), infants were not governed by her prior emotion. Infants behaved as if they expected the emoter to get angry only if she could see them performing the actions. These findings suggest that infants appreciate how people's visual experiences influence their emotions and use this information to regulate their own behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus intensity and the perception of duration.

This article explores the widely reported finding that the subjective duration of a stimulus is positively related to its magnitude. In Experiments 1 and 2 we show that, for both auditory and visual stimuli, the effect of stimulus magnitude on the perception of duration depends upon the background: Against a high intensity background, weak stimuli are judged to last longer. In Experiment 3 we show that the effect of intensity becomes more pronounced at longer durations, consistent with the idea that stimulus intensity affects the pacemaker component of an internal clock, and that it is the difference of a stimulus from the background, rather than its absolute magnitude, which influences the rate of the pacemaker. These results urge a modification to the oft-repeated claim that more intense stimuli seem to last longer, and provide an important constraint on any model of human timing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Searching for one or many targets: Effects of extended experience on the runs advantage.

Pigeons searched for any of several targets in experiments designed to explore attentional priming or search-image formation. Three experiments assessed the runs advantage, seen in improved search efficiency during single-target trial sequences compared with search efficiency during mixed-target sequences. Experiment 1 varied the number of items in the search display and the target set. Well-practiced pigeons showed the runs advantage only for a display size of 36 and a target set of 8. Experiments 2 and 3 followed the runs effect over training. For a target set of 4, the runs advantage was present initially but diminished with practice. For a target set of 12, the runs advantage persisted. The data suggest that learning permits a shift from controlled to automatic processing of memory, but constrains the number of items that can be addressed in parallel. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Molecular cloning and characterization of two related and interferon-induced 56-kDa and 30-kDa proteins highly similar to 2''-5'' oligoadenylate synthetase

The capability of subjects to categorize (as short or long) visually marked empty time intervals was investigated in three experiments. Two visual signals, located 18 degrees to the left (L) and to the right (R) of a fixation point in the visual field, established four marking conditions, two unilaterally presented (L-L and R-R) and two bilaterally presented (L-R and R-L). In Experiments 1 and 2, the results show that discrimination is better with unilateral sequences than with bilateral sequences and that the perceived duration is longer with an L-R than with an R-L sequence. In addition, Experiment 2 shows that, in comparison with a condition in which Markers 1 and 2 remain identical for a complete session, varying the markers from trial to trial does not decrease discrimination. Also, Experiment 2 shows that discrimination is better when both visual markers are presented at fovea than it is in the unilateral conditions. Experiment 3 shows that bilateral intervals are perceived as being longer and are better discriminated than are intervals marked by an intermodal sequence (auditory-visual or visual-auditory). The general discussion reports the implications of having different perceived duration and sensitivity levels, in various marker-type conditions, for an internal-clock hypothesis. Some implications of these results for a lateralized-timer hypothesis are also discussed.     

Learning and discrimination of audiovisual events in human infants: The hierarchical relation between intersensory temporal synchrony and rhythmic pattern cues.

This study examined 4- to 10-month-old infants' perception of audio-visual (A-V) temporal synchrony cues in the presence or absence of rhythmic pattern cues. Experiment 1 established that infants of all ages could successfully discriminate between two different audiovisual rhythmic events. Experiment 2 showed that only 10-month-old infants detected a desynchronization of the auditory and visual components of a rhythmical event. Experiment 3 showed that 4- to 8-month-old infants could detect A-V desynchronization but only when the audiovisual event was nonrhythmic. These results show that initially in development infants attend to the overall temporal structure of rhythmic audiovisual events but that later in development they become capable of perceiving the embedded intersensory temporal synchrony relations as well. (PsycINFO Database Record (c) 2010 APA, all rights reserved)