Auditory apparent motion in the free field: the effects of stimulus duration and separation.

The effects of stimulus duration and spatial separation on the illusion of apparent motion in the auditory modality were examined. Two narrow-band noise sources (40 dB, A-weighted) were presented through speakers separated in space by 2.5 degrees, 5 degrees, or 10 degrees, centered about the subject's midline. The duration of each stimulus was 5, 10, or 50 msec. On each trial, the sound pair was temporally separated by 1 of 10 interstimulus onset intervals (ISOIs): 0, 2, 4, 6, 8, 10, 15, 20, 50, or 70 msec. Five subjects were tested in nine trial block; each block represented a particular spatial-separation-duration combination. Within a trial block, each ISOI was presented 30 times each, in random order. Subjects were instructed to listen to the stimulus sequence and classify their perception of the sound into one of five categories: single sound, simultaneous sounds, continuous motion, broken motion, or successive sounds. Each subject was also required to identify the location of the first-occurring stimulus (left or right). The percentage of continuous-motion responses was significantly affected by the ISOI [F(9,36) = 5.67, p less than .001], the duration x ISOI interaction [F(18,72) = 3.54, p less than .0001], and the separation x duration x ISOI interaction [F(36,144) = 1.51, p less than .05]. The results indicate that a minimum duration is required for the perception of auditory apparent motion. Little or no motion was reported at durations of 10 msec or less. At a duration of 50 msec, motion was reported most often for ISOIs of 20-50 msec.(ABSTRACT TRUNCATED AT 250 WORDS)     

A comparison of the effects of spatial separation on apparent motion in the auditory and visual modalities

In the present investigation, the effects of spatial separation on the interstimulus onset intervals (ISOIs) that produce auditory and visual apparent motion were compared. In Experiment 1, subjects were tested on auditory apparent motion. They listened to 50-msec broadband noise pulses that were presented through two speakers separated by one of six different values between 0 degrees and 160 degrees. On each trial, the sounds were temporally separated by 1 of 12 ISOIs from 0 to 500 msec. The subjects were instructed to categorize their perception of the sounds as "single," "simultaneous," "continuous motion," "broken motion," or "succession." They also indicated the proper temporal sequence of each sound pair. In Experiments 2 and 3, subjects were tested on visual apparent motion. Experiment 2 included a range of spatial separations from 6 degrees to 80 degrees; Experiment 3 included separations from .5 degrees to 10 degrees. The same ISOIs were used as in Experiment 1. When the separations were equal, the ISOIs at which auditory apparent motion was perceived were smaller than the values that produced the same experience in vision. Spatial separation affected only visual apparent motion. For separations less than 2 degrees, the ISOIs that produced visual continuous motion were nearly equal to those which produced auditory continuous motion. For larger separations, the ISOIs that produced visual apparent motion increased.     

Auditory apparent motion under binaural and monaural listening conditions

This investigation examined the ability of listeners to perceive apparent motion under binaural and monaural listening conditions. Fifty-millisecond broadband noise sources were presented through two speakers separated in space by either 10 degrees, 40 degrees, or 160 degrees, centered about the subject's midline. On each trial, the sources were temporally separated by 1 of 12 interstimulus onset intervals (ISOIs). Six listeners were asked to place their experience of these sounds into one of five categories (single sound, simultaneous sounds, continuous motion, broken motion, or successive sounds), and to indicate either the proper temporal sequence of presentation or the direction of motion, depending on whether or not motion was perceived. Each listener was tested at all spatial separations under binaural and monaural listening conditions. Motion was perceived in the binaural listening condition at all spatial separations tested for ISOIs between 20 and 130 msec. In the monaural listening condition, motion was reliably heard by all subjects at 10 degrees and 40 degrees for the same range of ISOIs. At 160 degrees, only 3 of the 6 subjects consistently reported motion. However, when motion was perceived in the monaural condition, the direction of motion could not be determined.     

Evocation and characterization of percepts of apparent motion on the face

The percepts evoked by sequential stimulation of sites in close spatial proximity (<2.5 cm) on the face were studied. Both method-of-limits and magnitude-estimation procedures were used to identify and characterize alterations in the percepts produced by systematic changes in the temporal and spatial parameters of the sequence. Each site was stimulated by a vertically oriented row of miniature vibrating probes. Apparent motion was consistently perceived when the delay between the onsets of sequentially activated rows (interstimulus onset interval, or ISOI) fell within a relatively narrow range of values, the lower limit of which approximated 5 msec. Both the upper limit and the perceived smoothness and continuity of the motion percepts (goodness of motion) increased with the duration for which each row stimulated the skin over the range evaluated, 15–185 msec. For the successive activation of only two rows, goodness of motion was not influenced by changes in their separation from 0.4 to 2.5 cm. The ISOI values at which magnitude estimates of goodness of motion were highest increased with the duration for which each row stimulated the skin. As such, maximum goodness of motion decreased with increases in the apparent velocity of motion. When the number of sequentially activated rows was increased from two to four or more, the quality of the motion percepts improved. For the successive activation of multiple closely spaced rows, values of ISOI at which numerical estimates of goodness of motion were highest approximated integral fractions of the duration for which each row stimulated the skin. In this situation, the probes rose and fell in a regular, step-locked rhythm to simulate an edge-like or rectangular object moving across the skin. The goodness of motion so attained was relatively independent of the apparent velocity of motion.     

The effect of timing and spatial separation on the velocity of auditory apparent motion

Previously, it was shown that the minimum conditions for the illusion of auditory apparent motion (AAM) depend on stimulus timing but not spatial separation. In the present experiment, the effects of stimulus timing and source separation on the perceived velocity of AAM were examined. Eight listeners estimated the velocity, duration, and distance traveled of AAM, using a no-modulus, magnitude estimation procedure. Four burst durations (25, 50, 100, and 300 msec), 10 stimulus onset asynchronies (SOAs; 30, 40, 50, 60, 70, 80, 90, 100, 110, and 120 msec) and two separations (10° and 40°) were tested. Perceived velocity estimates were related to the total duration (burst duration + SOA) of the stimulus sequence. The effect of separation on velocity was extremely small but statistically significant. These results are similar to those obtained previously on the minimum conditions for AAM. Duration estimates were related only to total duration, but separation estimates were related to both separation and total duration. These results suggest that velocity is possibly a primary dimension of AAM that is independent of source separation.     

The slow formation of a pitch percept beyond the ending time of a short tone burst

The discriminability of short tone bursts differing in frequency was measured in terms of the sensitivity index d' as a function of interstimulus interval (ISI). The two stimuli presented on each trial consisted of either 6 or 30 sinusoidal cycles. When the frequency of the first stimulus varied randomly and widely from trial to trial (Experiment 1), discriminability was maximal for an ISI of about 400 msec in the 6-cycles condition and for a significantly longer ISI (of about 1 sec) in the 30-cycles condition. However, when the first stimulus had only two possible frequencies and the second stimulus was fixed (Experiment 2), the optimal ISI appeared to be about 400 msec in both conditions. A final experiment confirmed that, for tone bursts of 30 cycles, the optimal ISI was dependent on the perceptual uncertainty of the first stimulus. These results support the idea that the duration required to perceive the pitch of a sound as accurately as possible may far exceed the duration of the stimulus itself. More importantly, they indicate that the required duration is not a constant.     

Providing a sensory basis for models of visual information acquisition

Our major goal is to account for some simple digit-recall data with a theory that integrates two models from two scientific traditions. Therandom-sampling model, founded in the memory and attention literature, holds that (1) stimulus features are randomly sampled throughout the course of stimulus presence and (2) proportion correct recall is equal to the ratio of sampled features to total features.The linear-filter model, founded in the vision and sensation literature, holds that the initial stages of the visual system act as a low-pass temporal filter on the input stimulus, resulting in a time-varyingsensory response in the nervous system. We report two experiments in which a variable-duration, masked, four-digit string had to be immediately recalled. Experiment 1 was designed principally to replicate past data confirming the basic random-sampling model. Like others, we were able to confirm the model only by endowing it with an additionalprocessing-delay assumption: that feature sampling does not begin until the stimulus has been physically present for some minimal duration. Experiment 2 was an extension of Experiment 1 in which the target stimulus was preceded, 250 msec prior to its onset, by a 50-msec pre-presentation ofthe same stimulus called aprime. The Experiment 2 results allowed the following conclusions. First, the initial processing delay found in Experiment 1 is immutably tied to stimulus onset; that is, if there are two stimulus onsets, separated even briefly in time, there are two associated processing delays. Second, processing rate is essentially unaffected by the prime’s presentation. Third, being presented with a 50-msec prime is equivalent, in terms of memory performance, to increasing unprimed stimulus duration by approximately 30 msec; the prime can thus said to beworth 30 msec of additional exposure duration. This third conclusion seems superficially paradoxical, in the sense that one would expect that having seen a 50-msec prime would be equivalent to increasing exposure duration byat least the same 50 msec. However, both the initial processing delays and the 30-msec prime’s worth are natural consequences of our theory that conjoins the random-sampling model with the linear-filter model.     

Observer weighting of interaural delays in filtered impulses

Onset dominance in sound localization was examined by estimating observer weighting of interaural delays for each click of a train of high-frequency filtered clicks. The interaural delay of each click was a normal deviate that was sampled independently on each trial of a single-interval design. In Experiment 1, observer weights were derived for trains ofn=2, 4, 8, or 16 clicks as a function of interclick interval (ICI=1.8, 3.0, or 12.0 msec). For smalln and short ICI (1.8 msec), the ratio of onset weight to remaining weights was as large as 10. As ICI increased, the relative onset weight was reduced. For largen and all ICIs, the ongoing train was weighted more heavily than the onset. This diminishing relative onset weight with increasing ICI andn is consistent with optimum distribution of weights among components. Efficiency of weight distribution is near ideal when ICI=12 msec andn=2 and very poor for shorter ICIs and larger ns. Further experiments showed that: (1) onset dominance involves both within- and between-frequency-channel mechanisms, and (2) the stimulus configuration (ICI,n, frequency content, and temporal gaps) affects weighting functions in a complex way not explained by cross-correlation analysis or contralateral inhibition (Lindemann, 1986a, 1986b).     

Movement detection thresholds and stimulus duration

Movement detection thresholds were measured for varying exposures of a moving spot. A tradeoff was found in which an increase in duration (T) was offset by a decrease in the velocity required for detection (V). In the range of durations studied (about 50–700 msec), V × T was constant. The V × T constancy was interpreted in terms of the direct detection of movement as motion, and a comparison was made with Bloch’s law.     

The effect of stimulus availability on task choice in voluntary task switching

The voluntary task switching paradigm allows subjects to choose which task to perform on each trial in a stimulus environment affording multiple tasks. The present study examined the effect of stimulus availability on task choice. Subjects viewed displays containing a digit and a letter and performed either an even/odd or a consonant/vowel judgment on each trial. The target stimuli appeared with a stimulus onset asynchrony (SOA) of 0, 50, 100, or 150 msec. The probability of performing the task associated with Stimulus 1 increased as SOA increased, indicating an effect of external or stimulus-driven factors on task choice. This effect of stimulus availability on task choice was greater when the response-stimulus interval was 400 msec than when it was 2,000 msec. This interaction of preparation interval and stimulus availability is explained within a model of task choice that includes both internal processes and external influences.     

Immediate and delayed recognition of sequentially presented random shapes.

Two experiments tested whether short-term memory accounts for the recency effect observed with rapid sequential presentation of nonverbal stimuli. Four random shapes were presented sequentially (with no interstimulus interval) on each trial at rates of 150 msec, 250 msec, 500 msec, and 1,000 msec per stimulus. Subsequent recognition varied positively with exposure duration, ranging from 57% at 150 msec to 77% at 1,000 msec. Two serial position effects were observed: a slight decrease in recognition accuracy for the first stimulus in each sequence and a large increase in recognition for the last stimulus in each sequence. The recency effect was not altered by an intervening 30-sec delay, an intervening 30-sec copying task, or an intervening 30-sec copying and counting task. Since neither visual nor verbal distractors altered recognition accuracy, it was suggested that all shapes were processed directly into long-term memory storage. It also was hypothesized that long-term storage of a nonverbal stimulus requires identification of a distinctive feature of the stimulus and that this process may continue for a brief period after actual stimulus offset.     

On the relation between time and space in the visual discrimination of velocity.

Is the perception of velocity determined by the prior discrimination of spatial and temporal distances? Two experiments sought to answer this question by comparing the discriminabilities of moving stimuli varied in spatial extent, temporal duration, or in redundant combinations of both variables. The subject's task was to identify which of two alternative stimuli was presented on each trial. A set of four stimuli was constructed from two values of spatial extent and two values of temporal duration. Separate conditions required discrimination of each of the six possible pairs of these stimuli. Experiment 1 examined continuous motion and Experiment 2 examined apparent motion for stimuli with short (50 versus 65 msec) and with long (500 versus 650 msec) interstimulus intervals. With continuous motion and with good apparent motion (short intervals), the discrimination between the different-velocity bivariate pairs was too accurate to be attributed only to discriminations of the spatial and temporal extents of the motion. This did not occur with poor apparent motion. Evidently, time and space are perceptually related.     

When “I like you” indicates disagreement an experimental differentiation of information and affect

It was hypothesized that the independent manipulation of the informational content and the affective meaning of personal evaluations would indicate that both informational judgments and attraction responses are a joint function of the two stimulus components. In a 2 × 2 factorial design, each of 80 subjects was exposed to a videotape message from a stranger which was either affectively positive or negative and informationally positive or negative. Analysis of variance indicated that perceived similarity was influenced only by the informational variable (p < .0001) while attraction was influenced by both information (p < .0001) and affect (p < .002). It was suggested that the most inclusive theories of person perception and attraction will necessarily encompass elements of both cognitive and reinforcement formulations.     

Stroboscope motion: Effects of duration and interval1

The quality of stroboscope motion induced by the successive presentation of two illuminated squares obeys two rules. For all stimulus durations shorter than 100 msec, optimal motion occurs when the stimulus onsets differ by about 120 msec. For stimulus durations longer than 100 msec, optimal motion occurs when the second stimulus begins at the termination of the first stimulus. The two rules relating quality of motion to duration suggest a single principle, namely, that the quality depends only on the interval between the visual responses to the two stimuli. The interresponse interval at which motion is optimal is independent of stimulus duration.     

Concurrence costs in double stimulation tasks

Seven experiments are described on reaction time (RT₁) to a first auditory stimulus in a double stimulation paradigm, where the response to a second visual stimulus was explicitly non-speeded. In all studies it was found that, compared to a single stimulus control condition, RT₁ showed a constant delay of about 20–30 msec. The effect occurred irrespective of (a) the viewing conditions of the second stimulus in terms of either duration, processing demands or presence vs absence of a backward masking signal (experiments 1, 4, 5, 6, 7); (b) the duration of the interstimulus interval ranging from -200 msec up to at least a second (experiments 2, 3, 5); and (c) the processing demands of the first task (experiment 7). It is suggested that the delay reflects a basic concurrence cost which remains when two reactions can be time-shared.     

Early Feeding,Child Behaviour and Parenting as Correlates of Problem Eating

Mealtimes are a common source of stress for families. Examining factors related to problem eating may provide markers by which to identify families requiring assistance and salient targets for treatment. The current study investigated parenting practices and cognitions, generalisation of child behavioural issues, and early feeding history as they relate to problem eating in typically developing young children. We compared a community sample of 105 parents of 1.5–6-year-old children via survey and observation with 96 parents seeking treatment for their child’s problem eating. History of problems with breastfeeding, χ²(1)?=?3.88, p?=?.049, and the transition to solids, χ²(1)?=?7.27, p?=?.007, were more common among problem eaters than comparisons. Problem eaters had a greater number of problem behaviours outside of mealtimes, F(1181)?=?10.88, p?=?.001, though not more frequently than comparisons and not to clinical levels, F(1181)?=?1.81, p?=?.181. Parents of problem eaters reported more unhelpful mealtime parenting strategies, F(1155)?=?22.59, p?<?.001, yet general parenting style was similar by group, F(1187)?=?0.42, p?=?.527. Parents’ cognitions about mealtimes, F(1155)?=?119.81, p?<?.001, including mealtime-specific self-efficacy, F(1155)?=?171.30, p?<?.001, were poorer amongst problem eaters, and were the only factors to predict problem eating in the total sample. General parenting self-efficacy was poorer in parents of problem eaters (Behaviour: F(1187)?=?42.36, p?<?.001; Setting: F(1187)?=?10.64, p?=?.001). Evidence of feeding issues in infancy may support early detection of and intervention for later problem eating. The significance of broader child behaviour is less clear. Parent factors, particularly those specific to mealtimes, and cognitive in nature (including mealtime parenting self-efficacy) clearly differentiated the groups, and represent important targets for intervention.     

INCREASING EXTENDED CARE FACILITY RESIDENTS' ATTENDANCE AT RECREATIONAL ACTIVITIES WITH CONVENIENT LOCATIONS AND PERSONAL INVITATIONS1

Residents of extended care facilities generally exhibit a low level of attendance at recreational and therapeutic activities. Spatial arrangement of rooms, prompting, snacks, and small prizes have been suggested as factors that affect attendance. The present study examined the effects of an extensive system of prompts and the location of activity areas on the attendance of residents at a variety of activities. Twenty-six subjects were randomly selected from the ambulatory population of the facility. The first time each subject entered the activity room during the first 6 min of an activity session their name was recorded. Reliability measures were taken at 10 sessions, with a 95% mean agreement between observers. The variables examined were the amount of individualization of subjects (experimental group I: names announced versus experimental group 2: names not announced), room location (central or peripheral), use of names in announcements (activity only versus activity and group I names), and mode of announcement (PA system only versus PA system and in-person). A counter-balanced group design with repeated measures was used, with a randomly determined order of application of experimental treatments. An analysis of variance split plot 2.222 (Kirk, R. E. Experimental Design: Procedures for the Behavioral Science. Belmont, Ca.: Brooks-Cole, 1968.) of the level of subject attendance yielded significant main effects for room location, F(1, 24) = 5.47, p < 0.05, and type of announcement, F(1, 24) = 9.10, p < 0.01, and significant interactions for Individualization × Use of Names in Announcements, F(1, 24) = 5.57, p < 0.05, and Room Location × Mode of Announcement, F(1, 24) = 7.90, p < 0.01. The results indicate that using a centrally located room and announcement of resident names increases attendance at a variety of activities. The increased social and environmental interaction generated by activity attendance has potential therapeutic benefits for the residents involved. Furthermore, the kind of information reported here and by others should be taken into consideration by planners of a variety of group living facilities, ranging from nursing homes to residential treatment cottages.     

Single-letter recognition as a function of exposure duration

The time course of visual letter recognition was investigated in a single-stimulus identification experiment. On each trial, a randomly chosen stimulus letter was presented at 1 of 12 equiprobable positions that were equally spaced around the circumference of an imaginary circle centered on fixation. Exposure duration was varied from 10 to 200 ms, and the letter was followed by a pattern mask. The subject's task was to report the identity of the stimulus letter but refrain from guessing. For the briefest exposures, correct reports never occurred. For longer exposures, the function relating the probability p of recognizing the letter to the duration t of the stimulus exposure was well approximated by an exponential distribution function: p(t) = 1 − exp[−v·(t−t ₀)], where v is the rate of processing and t ₀ is the minimum effective exposure duration. The generality of this finding may be limited to cases in which stimuli are highly discriminable and response criteria are conservative. Extensions to Poisson counter or random walk models are considered for cases in which stimuli are confusable. Received: 1 July 1997 / Accepted: 2 July 1998     

Ultra-precise quantal timing: Evidence from simultaneity thresholds in long-range apparent movement

Conditions for the disappearance of long-range apparent movement were investigated. In an experiment on beta motion, critical interstimulus intervals (ISIs) of downward simultaneity thresholds for stimuli presented in continuous alternation were determined for exposure durations (EDs) varying from 3 to 160 msec. Each subject performed each test twice. Data were collected in three sessions, each for one of three angular separations (3°, 6°, and 12°) and the full set of EDs. The distribution of critical ISIs collapsed across subjects, EDs, and angular separations shows sharp maxima at regular distances within a range of 0–110 msec ISI. Significant or near-significant peaks were found at ISIs of 5, 9,22,27, 43, 55, and 107 msec. Although mean critical ISIs shifted with spatial separation, no essential shift of the main maxima occurred. Evidence of a periodic modulation with a period duration of 4.5 msec was obtained from the distributions of differences between critical ISIs of the first tests and their replications, which exhibit extremely low standard deviations (< 10 msec). These results agree well with previous analyses (Geissler, 1987, 1992) that led to a taxonomic model of quantal timing, briefly summarized in this paper. Further consequences are discussed and related to earlier developments (Geissler, 1991, 1992,1997).     

Differences in American English, Spanish, and monkey perception of thesay-stay trading relation

An interesting phenomenon in human speech perception is the trading relation, in which two different acoustic cues both signal the same phonetic percept. The present study compared American English, Spanish, and monkey listeners in their perception of the trading relation between gap duration andFl transition onset frequency in a syntheticsay-stay continuum. For all the subjects, increased gap duration caused perception to change fromsay tostay; however, subjects differed in the extent to which theFl cue traded with gap duration. For American English listeners, a change from a low to a highF1 onset caused a phoneme boundary shift of 26 msec toward shorter gap durations, indicating a strong trading relation. For Spanish listeners, the shift was significantly smaller at 13.7 msec, indicating a weaker trading relation. For monkeys, there was no shift at all, indicating no trading relation. These results provide evidence that thesay-stay trading relation is dependent on perceptual learning from linguistic exposure.