Auditory-visual interactions in the perception of a ball's path

We carried out two experiments to measure the combined perceptual effect of visual and auditory information on the perception of a moving object's trajectory. All visual stimuli consisted of a perspective rendering of a ball moving in a three-dimensional box. Each video was paired with one of three sound conditions: silence, the sound of a ball rolling, or the sound of a ball hitting the ground. We found that the sound condition influenced whether observers were more likely to perceive the ball as rolling back in depth on the floor of the box or jumping in the frontal plane. In a second experiment we found further evidence that the reported shift in path perception reflects perceptual experience rather than a deliberate decision process. Instead of directly judging the ball's path, observers judged the ball's speed. Speed is an indirect measure of the perceived path because, as a result of the geometry of the box and the viewing angle, a rolling ball would travel a greater distance than a jumping ball in the same time interval. Observers did judge a ball paired with a rolling sound as faster than a ball paired with a jumping sound. This auditory-visual interaction provides an example of a unitary percept arising from multisensory input.     

Accuracy of temporal coding: Auditory-visual comparisons

Three experiments were designed to decide whether temporal information is coded more accurately for intervals defined by auditory events or for those defined by visual events. In the first experiment, the irregular-list technique was used, in which a short list of items was presented, the items all separated by different interstimulus intervals. Following presentation, the subject was given three items from the list, in their correct serial order, and was asked to judge the relative interstimulus intervals. Performance was indistinguishable whether the items were presented auditorily or visually. In the second experiment, two unfilled intervals were defined by three nonverbal signals in either the auditory or the visual modality. After delays of 0, 9, or 18 sec (the latter two filled with distractor activity), the subjects were directed to make a verbal estimate of the length of one of the two intervals, which ranged from 1 to 4 sec and from 10 to 13 sec. Again, performance was not dependent on the modality of the time markers. The results of Experiment 3, which was procedurally similar to Experiment 2 but with filled rather than empty intervals, showed significant modality differences in one measure only. Within the range of intervals employed in the present study, our results provide, at best, only modest support for theories that predict more accurate temporal coding in memory for auditory, rather than visual, stimulus presentation.     

Auditory-visual conflicts in the perceived duration of lights, tones and gaps

The perceived duration of a short tone (1,000 or 1,500 msec) was longer than that of a separately presented light of equal length. Thus, when light and tone were presented simultaneously, there was a conflict in perceived duration. In that case, the perceived duration of an interval filled with both light and tone was close to that of an interval filled with tone alone. A silent gap in otherwise continuous tone was perceived as longer than a gap in otherwise continuous light, and the perceived duration of a gap occurring simultaneously in both light and tone was close to that of a gap in tone alone. Thus, auditory dominance occurred under the preceding conditions-that is, auditory-visual conflicts in perceived duration, whether occurring between filled intervals or gaps, were resolved in favor of the auditory modality. Visual dominance occurred only under one condition, in which the intensity of tone was reduced, and in which the perceived duration of a 500-msec light was longer than that of a 500-msec tone. The finding of auditory dominance in the perception of time runs counter to the results of studies of sensory conflicts in spatial perception, where vision typically dominates audition and touch.     

Discrimination of coronal stops by bilingual adults: the timing and nature of language interaction

The current study was designed to investigate the timing and nature of interaction between the two languages of bilinguals. For this purpose, we compared discrimination of Canadian French and Canadian English coronal stops by simultaneous bilingual, monolingual and advanced early L2 learners of French and English. French /d/ is phonetically described as dental whereas English /d/ is described as alveolar. Using a categorial AXB task, the performance of all four groups was compared to chance and to the performance of native Hindi listeners. Hindi listeners performed well above chance in discriminating French and English /d/-initial syllables. The discrimination performance of advanced early L2 learners, but not simultaneous bilinguals, was consistent with one merged category for coronal stops in the two languages. The data provide evidence for interaction in L2 learners as well as simultaneous bilinguals; however, the nature of the interaction is different in the two groups.     

Auditory-visual intermodal matching of small numerosities in 6-month-old infants

Recent studies have reported that preverbal infants are able to discriminate between numerosities of sets presented within a particular modality. There is still debate, however, over whether they are able to perform intermodal numerosity matching, i.e. to relate numerosities of sets presented with different sensory modalities. The present study investigated auditory-visual intermodal matching of small numerosities in infancy by using a violation-of-expectation paradigm. After being familiarized with events of a few objects impacting a surface successively, 6-month-old infants were alternatively presented with two and three tones while the movement of each object remained hidden behind an opaque screen. The screen was then removed to reveal either two or three objects. Results showed that the infants looked significantly longer at the numerically nonequivalent events (the three-tone/two-object and the two-tone/three-object events) than at the numerically equivalent events (the two-tone/two-object and the three-tone/three-object events) irrespective of the rate or duration of auditory tones presented. These findings suggest that infants are capable of performing intermodal matching of small numerosities and that they might possess abstract representations of numerosity beyond sensory modalities.     

Withholding inputs in team contexts: member composition, interaction processes, evaluation structure, and social loafing

Social loafing was observed as a naturally occurring process in project teams of students working together for 3-4 months. The authors assessed the contributions that member composition (i.e., relational dissimilarity and knowledge, skills, and abilities; KSAs), perceptions of the team's interaction processes (i.e., dispensability and the fairness of the decision-making procedures), and the team's evaluation structure (i.e., identifiability) make toward understanding loafing behavior. Identifiability moderated the impact of dispensability on loafing but not the impact of fairness on loafing. Perceptions of fairness were negatively related to the extent that participants loafed within their team. Specific aspects of relational dissimilarity were positively associated with perceptions of dispensability and negatively associated with perceptions of fairness, whereas KSAs were negatively associated with perceptions of dispensability.     

Protestant ethic endorsement and the fairness of equity inputs

Two studies are reported which show how endorsement of the Protestant ethic is related to the perceived fairness of using various equity inputs. In Experiment 1, male undergraduates scoring high and low on the Protestant Ethic (PE) Scale made salary decisions for hypothetical workers who differed with respect to their performance quantity and duration. High PEs paid workers in proportion to their total productivity by taking into account both quantity and duration. However, low PEs ignored differences in quantity by paying workers the same amount, but did pay in proportion to duration. In the follow-up study, high PEs reported that it is fairer to base reward on performance when differences are attributable to internal causes than external causes, while the reverse was found for low PEs.     

Rhythm and the timing of movement sequences

Summary Many motor skills involve a sequence of movements phased over a period of time. The present study investigated the importance of rhythmic timing structures in the acquisition and control of a serial key-pressing task. Four groups of subjects received extensive practice on 9-element finger sequences varying in the form of the inherent temporal structure. Following a training period, the stability of the various timing patterns was examined by requiring subjects to perform the key-pressing task concurrently with a verbal memory task. The memory task involved reporting back a sequence of visually-presented words with a lag of one word. A comparison was made of performance on the two tasks under dual task and control (single task) conditions. The results suggested that natural rhythmic timing structures require less attention for production than unnatural temporal patterns. A breakdown of the temporal patterns into within-group and between-group intervals showed that patterns containing within-group intervals that related as 1:1 or 1:2 evidenced good stability under dual-task conditions. These results were taken as support for the suggestion by Fraisse (1946) that the perception and production of rhythms can be understood by an internal representation that allows only two distinct durations that relate as 1:2. Furthermore, it was suggested that relative timing may become an invariant property of motor program representation only in those instances in which the timing sequence completely fits the internal timing structure.     

Multiple timing and the allocation of attention

Two experiments were designed to examine the effects of multiple timing tasks on prospective time judgment performance. In experiment 1, subjects were required to monitor the durations of one, two, three, or four concurrent target stimuli which began and ended at different times, and then reproduce one of those durations subsequently chosen at random. Time judgment accuracy deteriorated as the number of target stimuli increased. In experiment 2, subjects used the production method to generate specified durations for one, two, three, or four partially overlapping stimuli. Timing was less accurate in conditions involving more target stimuli. In the multiple-target conditions, time judgments were less accurate for the later- rather than earlier-onset targets. The results support an attentional model of timing, and suggest that timing is an effortful process which draws from limited attentional resources.     

Force and timing components of the motor program

Three experiments were undertaken to assess the effects of variations of force and time on both simple and choice reaction time. The first two experiments demonstrated that although latency did not vary as a function of force, timing variations, such as requiring that a response be maintained, led to consistent changes in reaction time. These results led to the development of a model of motor programming in which force and timing are dissociated as separate components. However, the data also indicated that the force component may be further analyzed into two subcomponents-force activation and force deactivation. The model predicts that the latter subcomponent may be programmed on-line provided that sufficient time elapses between the implementation of the two subcomponents. A different pair of movements was used in Experiment 3 to further demonstrate that force activation and deactivation may be preprogrammed into a single component. These results support the aspect of the proposed model that makes a distinction between operations required for program construction from those necessary for program implementation.     

Cardiac timing and the central regulation of action

The central control of information processing necessarily entails a selection between actions that are implicit in different processing streams. We argue that this selection for action also adjusts the autonomic support for action. When actions are transiently undefined during the transition between actions, the time between heartbeats increases (heart rate transiently slows). This is particularly clear when actions are imminent but their identity is undefined, e.g. due to a delay while prepotent actions are inhibited in order to map a required action. We review results from a number of experiments supporting this perspective. These results suggest that central inhibition of representations of action influences heartbeat timing as well as more peripheral inhibition of overt responses. Given that inhibitory processes characteristic of central response selection induce transient heartbeat slowing, then this change is an interesting converging measure of the state of central response selection in combination with performance measures.     

An analysis of a performance feedback system: the effects of timing and feedback, public posting, and praise upon academic performance and peer interaction

In the first experiment, after establishing baseline composition rates in each classroom, timing (announcing time limits) and feedback (student self-scoring) were introduced followed by the introduction, removal, and reintroduction of public posting of highest scores. Timing and feedback improved story writing performance and public posting of highest scores improved performance even further in both classrooms. Teacher praise produced further improvement in one classroom but had no effect on performance in the other. Changes in on-task behavior paralleled changes in writing rate. Comments made by children concerning their own work or work of their peers were recorded throughout the experiment. Although the baseline rate of performance comments was almost zero, the introduction of each variable markedly increased the rate of performance comments. In the second experiment, baseline rates on reading and language exercises were established in a fifth-grade classroom. The entire performance feedback system was introduced on a multiple baseline across the two behaviors and then removed during the final phase of the experiment. Introducing the system improved performance on both tasks. These results further increased the generality of some of the findings of the previous experiment and of previous research on the efficacy of the experimental package of timing, feedback, public posting, and praise.