Richard J. Jagacinski

Tests of Parallel Versus Integrated Structure in Polyrhythmic Tapping

Musically trained subjects tapped three beats with their right hand versus two beats with their left hand in synchrony with two corresponding tones. For independent groups of subjects, the pitch difference of the two tones was either small to encourage an integrated perceptual organization or large to encourage a streamed perceptual organization. Integrated versus parallel motor organization was tested by examining the pattern of covariances among intertap intervals. All subjects exhibited integrated motor organization. An integrated multiplicative hierarchical model of motor organization was superior to a serial chained model and to an independent hierarchical model in describing the pattern of covariances. The subjects who heard tones that encouraged an integrated percept performed with less variability than the subjects who heard tones that encouraged a streamed percept. This superior performance with an integrated motor organization and an integrated rather than a streamed perceptual organization is interpreted as evidence for temporal perceptual-motor compatibility.

On marching to two different drummers: perceptual aspects of the difficulties

People have remarkable difficulty generating two responses that must follow different temporal sequences, unless the temporal patterns are simply related (e.g., periods in 2:1, 3:1 relation). For example, it is hard to tap to two conflicting rhythms presented concurrently (i.e., a polyrhythm) using the right and left hands (Klapp, 1979), or to tap while articulating a conflicting speech utterance (Klapp, 1981). The present experiments indicate that difficulties in processing conflicting rhythms occur even when people must (a) merely monitor the stimuli and indicate the termination of one rhythmic sequence or (b) tap with a single hand. Responding to polyrhythms is thus difficult even without multiple limb coordination. Furthermore, the difficulty of two-handed tapping to polyrhythms that involve two different tones was found to decrease as the pitch difference between the tones was decreased. This result indicates that the difficulty of rhythmic coordination can be perceptually manipulated in a striking fashion. Polyrhythmic performance thus provides an excellent opportunity for examining possible interactions of perceptual and motor organizations.

Supervisory control in a dynamic and uncertain environment: a process model of skilled human-environment interaction

An understanding of how both psychological and environmental factors mutually constrain skilled behavior is required to effectively support human activity. As a step toward meeting this need, a process model of skilled human interaction with a dynamic and uncertain environment is presented. The model was able to mimic human behavior in a laboratory task requiring one- and two-person crews to direct the activities of a fleet of agents to locate and process valued objects in a simulated world. The process model is a pair of highly interactive components that together mimic the behavior of the human-environment system. One component is a representation of the external environment as a dynamically changing set of opportunities for action. The second component is a dynamic representation of skilled human decision making and planning behavior within the environment so described. The process model is an expression of a general theory of skilled interaction assuming that perception and action mechanisms sensitive to environmental constraints are responsible for generating much of behavior, and where the need for additional cognitive processing of internal representations may result from environmental designs that do not adequately support the perceptual guidance of activity. >

A Qualitative Look at Feedback Control Theory as a Style of Describing Behavior

The present paper reviews several ways feedback control theory has been used to describe tracking behavior and several qualitative experimental techniques. These techniques require only ordinal-level measurement and may aid any researcher investigating behavior whose temporal patterning is critical and which involves fairly continuous changes over time. One possible application in the area of stuttering behavior is presented in detail to show how these techniques can provide useful insights and hypotheses. Other suggested areas of application include the behavior of human social groups, motivational behavior, and emotional behavior.

Describing the Human Operator's Internal Model of a Dynamic System

An analysis of phase-plane switching loci was used to infer the human operators internal model of a dynamic system he was attempting to control. Striking differences were found between the internal model and the actual dynamic system, and the internal model exhibited orderly changes with practice. The difficulties involved in incorporating a non-veridical internal model into optimal control models of the human operator are discussed.

Can people tap concurrent bimanual rhythms independently

If people could tap 2 rhythms independently, 1 rhythm with each hand, training people to tap the rhythms separately should enable them to tap the rhythms concurrently. However, nonmusician participants in the present experiments were unable to produce accurate intervals when lapping bimanually after they had mastered the rhythms individually. That finding implies that tapping concurrent rhythms requires an integrated sensory-motor representation incorporating the actions of both hands into a single pattern. Although training the rhythms separately cannot specify an integrated code, such specification is possible with bimanual training. Bimanual training quickly led to accurate tapping, but most participants then did not tap correctly either of the separate rhythms that had been mastered in the context of concurrent tapping. That finding suggests that the integrated representation does not code either rhythm independently.

TESTS OF ATTENTIONAL FLEXIBILITY IN LISTENING TO POLYRHYTHMIC PATTERNS

Four experiments examined attentional flexibility in listening to polyrhythmic patterns. Musically trained and untrained listeners detected changes in timing of 1 tone (the lower tone) in a 3:2 polyrhythm in which high and low tones varied in frequency separation. Experiment 1 encouraged integrative attending; all listeners performed significantly poorer in conditions with wide as opposed to narrow frequency separations. Experiment 2, which encouraged selective attending to low tones, reversed these results: Performance was poorer in the narrow frequency conditions. In neither experiment did skill interact with frequency separation. Experiments 3 and 4 extended these findings to moderate frequency separations. Over all experiments, musically trained listeners exhibited an enhanced ability to detect timing variations, but not flexibility of perceptual organization as it applies to detection of timing changes. Instead, pattern structure (e.g., frequency and time relation) decisively influenced perception for both levels of skill.

Gestalt principles in the control of motor action.

We argue that 4 fundamental gestalt phenomena in perception apply to the control of motor action. First, a motor gestalt, like a perceptual gestalt, is holistic in the sense that it is processed as a single unit. This notion is consistent with reaction time results indicating that all gestures for a brief unit of action must be programmed prior to initiation of any part of the movement. Additional reaction time results related to initiation of longer responses are consistent with processing in terms of a sequence of indivisible motor gestalts. Some actions (e.g., many involving coordination of the hands) can be carried out effectively only if represented as a unitary gestalt. Second, a perceptual gestalt is independent of specific sensory receptors, as evidenced by perceptual constancy. In a similar manner a motor gestalt can be represented independently of specific muscular effectors, thereby allowing motor constancy. Third, just as a perceptual pattern (e.g., a Necker cube) is exclusively structured into only 1 of its possible configurations at any moment in time, processing prior to action is limited to 1 motor gestalt. Fourth, grouping in apparent motion leads to stream segregation in visual and auditory perception; this segregation is present in motor action and is dependent on the temporal rate. We discuss congruence of gestalt phenomena across perception and motor action (a) in relation to a unitary perceptual-motor code, (b) with respect to differences in the role of awareness, and (c) in conjunction with separate neural pathways for conscious perception and motor control.

Generalized slowing in sinusoidal tracking by older adults

Older and younger adults manually tracked sinusoidal input signals. Older adults exhibited 2 forms of slowing. First, they lagged behind the target somewhat more than younger adults. Second, they made considerably smaller movements than the younger adults. Because the velocity of a sinusoidal pattern is proportional to its amplitude, these smaller movements were also slower. Both older and younger adults made smaller movements with a compensatory display and with higher frequency inputs. The high degree of proportionality among these effects was taken as evidence for generalized slowing by the older adults. This slowing may prevent older adults from successfully adjusting an internal pattern generator to match their motions to the sinusoidal input signal.

Quantifying the performance limitations of older and younger adults in a target acquisition task

In a stationary target acquisition task, both 65-year-old and 20-year-old adults exhibited a negatively accelerated curvilinear relationship between the spatial variability of submovement endpoints and average submovement velocity. For high velocities, the variability was greater for the older adults. This elevated motor noise is considered a primary cause of their slower performance. Both age groups also exhibited a linear relationship between submovement duration and the logarithm of submovement relative accuracy. A stochastic model indicates that the two age groups were similar in the strategies they used to compose single movements from a variety of submovements. However, when performing sequences of movements containing varied target distances, older adults exhibited a repetition effect whereas younger adults exhibited a contrast effect. Older adults may plan movements individually, whereas younger adults plan sequences.