Biomedical subjects

Nancy S Hemmes

Publications and source records attributed to Nancy S Hemmes.

7 recordsLinked to original sources

PubMed2006

The effect of intruded events on peak time: the role of reinforcement history during the intruded event.

Pigeons were studied in an extension of a study by Aum et al. [Aum, S., Brown, B.L., Hemmes, N.S. 2004. The effects of concurrent task and gap events on peak time in the peak procedure. Behav. Process. 65, 43-56] on timing behavior under a discrete-trial fixed-interval (FI) procedure during which 6-s intruded events were superimposed on peak-interval (PI) test trials. In Aum et al., one event consisted in termination of the timing cue (gap trial); the other was a stimulus in the presence of which subjects had been trained to respond under an independent random-interval (RI) schedule of reinforcement (concurrent task trial). Aum et al. found a disruption of timing on concurrent task trials that was greater than that on gap trials. The present study investigated history of reinforcement associated with intruded events as a possible explanation of this earlier finding. After training to peck a side key on a 30-s PI procedure, discrimination training was conducted on the center key in separate sessions; red or green 6-s stimuli were associated with RI 24s or EXT (extinction) schedules. During testing under the PI procedure, three types of intruded events were presented during probe trials--the stimulus associated with the RI (S+) or EXT (S-) schedule during discrimination training, or a gap (termination of the side-keylight). Intruded events occurred 3, 9, or 15s after PI trial onset. Effects of reinforcement history were revealed as substantial disruption of timing during the S+ event and relatively little disruption during the S- event. Intermediate effects were found for the gap event. Results indicate that postcue effects are at least partially responsible for the disruptive effects of the S+ event.

Analysis of Variance↗

PubMed2005

Effects of the contingency for homework submission on homework submission and quiz performance in a college course.

Effects of the contingency for submission of homework assignments on the probability of assignment submission and on quiz grades were assessed in an undergraduate psychology course. Under an alternating treatments design, each student was assigned to a points condition for 5 of 10 quiz-related homework assignments corresponding to textbook chapters. Points were available for homework submission under this condition; points were not available under the no-points condition. The group-mean percentage of homework assignments submitted and quiz grades were higher for all chapters under the points condition than in the no-points condition. These findings, which were replicated in Experiment 2, demonstrate that homework submission was not maintained when the only consequences were instructor-provided feedback and expectation of improved quiz performance.

Adult↗

PubMed2004

Prospective timing under dual-task paradigms: attentional and contextual-change mechanisms.

The effect of a concurrent memory task on prospective time estimates by human participants was investigated in two experiments. The objective was to isolate task effects from those of participant timing strategy (self-paced counting) and number of contextual changes during the temporal stimulus. Accordingly, self-paced counting was suppressed by requiring participants to perform a word-reading task during the temporal stimuli, while number of stimulus changes presented during temporal stimuli was controlled. Presence versus absence of the concurrent memory task was manipulated in Experiment 1, and instruction to focus on timing or to focus on memory was manipulated in Experiment 2. There was no significant effect of presence versus absence of the concurrent memory task on time estimates; however, time estimates were shorter when participants were instructed to focus on memory versus timing. In both experiments, time estimates were positively correlated with participants' estimates of the number of words presented during the interval, even though number of words presented was invariant. These findings were generally consistent with resource-allocation attentional accounts of concurrent task effects; however, support for a contextual-change model of timing was also obtained.

Adolescent↗

PubMed2004

The effects of concurrent task and gap events on peak time in the peak procedure.

The effect of a concurrent task on timing performance of pigeons was investigated with the peak interval procedure. Birds were trained to peck a side key on a discrete-trial schedule that included reinforced fixed-interval (FI) 30-s trials and nonreinforced extended probe trials. Then, in separate sessions, birds were trained to peck a 6-s center key for food. In a subsequent test phase, the FI procedure was in effect along with dual-task probe test trials. On those test trials, the 6-s center key (task cue) was presented at 3, 9, or 15s after probe trial onset. During another test phase, a 6-s gap (the FI keylight was extinguished) was presented at 3, 9, or 15s after probe trial onset. Peak time increased with center key time of onset, and was greater under task than gap conditions. Moreover, peak time under task conditions exceeded values predicted by stop and reset clock mechanisms. These results are at variance with current attentional accounts of timing behavior in dual-task conditions, and suggest a role of nontemporal factors in the control of timing behavior.

Animals↗

PubMed2004

Gross-motor skill acquisition by preschool dance students under self-instruction procedures.

The effects of two training procedures--(a) modeling and praise and (b) self-instruction, modeling, and praise--on complex gross-motor chain acquisition for preschool dance class students were evaluated. Six girls participated in the study. A multiple baseline design across six gross-motor chains with a secondary group comparison for treatment order effects was used. Both procedures were effective in teaching the gross-motor chains. Nevertheless, for 4 of the 6 participants, the self-instruction procedure produced a faster acquisition rate in at least two of the three comparable pairs of gross-motor chains. Furthermore, very early in gross-motor chain acquisition, for five of the six gross-motor chains, the self-instruction condition was associated with faster response acquisition.

Child, Preschool↗

PubMed2004

Time perception with and without a concurrent nontemporal task.

Prospective time estimates were obtained from human subjects for stimulus durations ranging from 2 to 23 sec. Presence and absence of a concurrent nontemporal task was manipulated within subjects in three experiments. In addition, location of the task within temporal reproduction trials and psychophysical method were varied between groups in Experiments 2 and 3, respectively. For long-duration stimuli, the results of all three experiments conformed to results in the literature, showing a decrease in perceived duration under concurrent task conditions, in accord with attentional resource allocation models of timing. The effects of task location and psychophysical method on time estimates were also compatible with this analysis. However, psychophysical functions obtained under task conditions were fit well by power functions, an outcome that would not be anticipated on the basis of attention theory. The slopes of the functions under no-task conditions were steeper than those under task conditions. The data support the perceptual hypothesis that different sources of sensory input mediate timing under task and no-task conditions.

Adolescent↗

PubMedDate not supplied

Increases in social initiation toward an adolescent with autism: reciprocity effects.

Level of spontaneous social initiating by three adult caregivers toward a youth with autism was studied during a program to increase the youth's level of social initiating. The adult participants were three staff members of a program for individuals with autism; they were assigned to the classroom of the youth participant, but none was directly involved in his educational program. Under a multiple-baseline across subject design, in combination with a multi-element design, the youth's social initiations toward each adult were systematically reinforced. Two sessions were conducted daily: one in which prompts, token reinforcers, and verbal praise for the youth's social behavior were presented (baseline and training sessions), and one in which prompts were absent and only verbal praise was presented (probe sessions). Frequency of spontaneous initiating toward the youth increased for each adult during treatment when the youth's frequency of initiating toward a given adult increased. It was higher during training vs. probe sessions, where level of social initiating by the youth was also higher.

Adolescent↗