Stimulus repetition effects and the dimension-feature distinction in alternative targets

The negative repetition effect (NRE) refers to a poorer perception of the target in noise-same-as-target than in noise-alternative-target displays. Using the parenthesis as target and noise that are either identical or different in orientation, we tested predictions derived from a feature-specific inhibition model (Bjork & Murray, 1977) that explains the NRE as arising from inhibitory interactions among channels handling identical inputs. Contrary to our expectation of evidence for orientation-specific inhibition, a positive repetition effect (PRE) was observed. We also found a PRE for the dimension target sets whose stimuli differ only in orientation and an NRE for the feature target sets whose stimuli differ in the number of elements. Further experiments that systematically varied relationships between alternative targets indicate that these basic findings, termed the stimulus attributes effects, do not arise from pattern masking, perceptual strategies, or response bias.     

Stimulus repetition effects on texture-based visual search by pigeons

Four experiments investigated the effects of within-session stimulus repetition on texture discrimination. Six pigeons (Columba livia) searched for a contrasting target region (color or shape) randomly embedded within a larger distractor region for food reinforcement. Experiment 1 found that repeating features of the distractors, but not those of the target, across trials increased the accuracy of target localization relative to baseline. Experiment 2 found that subsequently switching the identity of a repeated distractor feature to the target decreased accuracy. Experiment 3 found that the effects of repeating a distractor feature influenced search performance for at least 60 trials after this learning. Experiment 4 found that differential stimulus-outcome relations can produce control by repeated target features. The results are discussed in terms of the factors and strategies involved in the control of avian visual search behavior.     

Stimulus and temporal cues in classical conditioning

In 2 experiments, separate groups of rats were given stimulus conditioning, temporal conditioning, untreated control and (in Experiment 2) learned irrelevance control procedures, followed by a compound with both stimulus and temporal cues. Stimulus conditioning consisted of a random 15-s duration conditioned stimulus (CS) followed by food; temporal conditioning consisted of food-food intervals of fixed 90 s (Experiment 1) or fixed 75 + random 15 s (Experiment 2). The stimulus group abruptly increased responding after CS onset, and the temporal group gradually increased responding over the food-food interval. When the food-food interval was fixed 90 s, the temporal cue exerted stronger control in the compound, whereas when the food-food interval was fixed 75 + random 15 s, the stimulus cue exerted stronger control. The strength of conditioning, temporal gradients of responding, and cue competition effects appear to reflect simultaneous timing of multiple intervals.     

Stimulus and response repetition effects for naming letters at two response-stimulus intervals

Upper- and lower-case letters of the alphabet were presented sequentially to S using .2-sec and. 7-sec RSIs. Reaction times for naming the letters were recorded for three classes of stimulus events: the letter was identical in form and name to the immediately preceding one (stimulus repetitions); the letter had the same name but a different form than the preceding one (response repetitions); and the letter was different in form and name from the preceding one (nonrepetitions). The results showed a significant advantage of SR over RR that decreased as the RSI increased and depended on the similarity of the upper and lower cases for the particular letters. These results are comparable to those obtained in letter-matching studies. A model to account for the results is proposed.     

Stimulus and response contributions to the children's reaction-time repetition effect

Adults and 8-, 10-, 12-, and 14-year olds completed a serial reaction-time task with two stimuli mapped to each of two responses and 100-, 500-, and 1000-msec response-stimulus intervals (RSIs). Trials were classified as (1) identical (same stimulus and same response on two consecutive trials), (2) response equivalent (different stimulus but same response on two consecutive trials), or (3) different (different stimulus and different response on two consecutive trials). Identical and different trials were compared as a general indication of repetition effects. Response-equivalent minus identical reaction time identified stimulus contributions, and different minus response-equivalent reaction time identified response contributions. Adults received a repetition advantage at all RSIs and children received a repetition advantage at 500- and 1000- but not 100-msec RSIs. Stimulus contributions accounted for the repetition effect for both adults and children. At the 500- and 1000-msec RSIs, both the overall repetition effect and stimulus contribution were positive and decreased in magnitude as age increased. The response contribution was independent of RSI and was negative for 8- and 10-year-olds and near zero or positive for older performers. At the longer RSIs, positive stimulus contributions were sufficient to overcome the negative response contributions present for younger children.     

Stimulus control of responding by response-reinforcer temporal contiguity

The stimulus properties of brief disruptions in response-reinforcer temporal contiguity were investigated using a discrete trial conditional discrimination procedure. Key pecking (nondelay) or key pecking followed by a brief interval of nonpecking (delay) in the sample component produced a stimulus change (choice component). Pecks in the choice component to one of two alternatives resulted in food or blackout, conditional upon which response requirement was met in producing the choice component. A baseline condition, in which key pecking always produced the choice component and correct choices were arranged randomly, alternated with experimental conditions that included nondelay and delay values of either 0.2, 0.5, or 1.0 sec between the last key peck and the initiation of the choice component. All subjects accurately discriminated brief temporal delays between a response and stimulus change, with choice accuracy increasing for three of four subjects as the temporal disruption in contiguity increase. Implications of the research for the study of delayed reinforcement, response-independent reinforcement, and the discrimination of causality are discussed.     

Effects of association and repetition in memory for temporal order

Temporal order recognition memory has been examined previously with tasks involving a recency judgment between a pair of items in a preceding string. Recency judgments are impaired when the earlier item is repeated. The present study employed the comparative recency judgment paradigm, with the lists composed of words. The effect of the inclusion in the list of a high associate of the earlier test item was examined and compared to the effect of repetition. Associative interference was observed, but not in all conditions. Direction of association was a significant factor. The results were interpreted in terms of a model of word recognition proposed by Morton.     

Counting eliminates the repetition effect in judgments of temporal duration.

College student subjects estimated the duration of time intervals (8–54 sec) by counting or not (N=35 per group). Counting eliminated the repetition effect (a decline in the magnitude of estimations across trials), and resulted in a truncation of the psychophysical function. The former result was interpreted as contrary to Treisman's (1963) model. The latter result was attributed to the effortfulness of counting, which was established in a subsequent experiment.     

Auditory temporal pattern learning by songbirds using maximal stimulus diversity and minimal repetition

The sequential patterning of complex acoustic elements is a salient feature of bird song and other forms of vocal communication. For European starlings (Sturnus vulgaris), a songbird species, individual vocal recognition is improved when the temporal organization of song components (called motifs) follows the normal patterns of each singer. This sensitivity to natural motif sequences may underlie observations that starlings can also learn more complex, unnatural motif patterns. Alternatively, it has been proposed that the apparent acquisition of abstract motif patterning rules instead reflects idiosyncrasies of the training conditions used in prior experiments. That is, that motif patterns are learned not by recognizing differences in temporal structures between patterns, but by identifying serendipitous features (e.g., acoustical cues) in the small sets of training and testing stimuli used. Here, we investigate this possibility, by asking whether starlings can learn to discriminate between two arbitrary motif patterns, when unique examples of each pattern are presented on every trial. Our results demonstrate that abstract motif patterning rules can be acquired from trial-unique stimuli and suggest that such training leads to better pattern generalization compared with training with much smaller stimulus subsets.     

Maturation of rapid auditory temporal processing and subsequent nonword repetition performance in children

According to the rapid auditory processing theory, the ability to parse incoming auditory information underpins learning of oral and written language. There is wide variation in this low-level perceptual ability, which appears to follow a protracted developmental course. We studied the development of rapid auditory processing using event-related potentials (ERPs) elicited by tone pairs presented at varying inter-stimulus intervals (25, 50, 100, 200, and 400 ms) in a sample of children (N = 103) aged 7-9 years initially and again at 9-11 years. We also assessed their ability to repeat nonsense words at both time-points. The amount of difference between the ERP to single tones and paired tones (as assessed by the intra-class correlation coefficient, ICC) provided a measure of the brain's capacity to discriminate auditory information delivered at different presentation rates. Results showed that older children showed greater neural discrimination to tone pairs than younger children at rapid presentation rates, although these differences were reduced at slower presentation rates. The ICC at time 1 significantly predicted nonword repetition scores two years later, providing support for the view that rapid auditory temporal processing ability affects oral language development in typically developing children.     

On Stimulus Generalization and Stimulus Classes

Stimulus generalization has been defined as the spread of effect of reinforcement for responses emitted in the presence of one stimulus to different stimuli presented under extinction conditions. As a result of stimulus generalization, novel stimuli come to exert stimulus control over members of the response class. Studies in the applied behavior analysis literature, however, have reported experimental preparations that included prompting and reinforcement procedures during what were claimed to be stimulus generalization conditions. These studies violated the procedural requirement that stimulus generalization be tested under extinction conditions. Responses that come under the control of a class of stimuli may do so by direct training or by stimulus generalization. It is desirable for organisms to respond in the presence of members of an appropriately constructed stimulus class, but we should understand the mechanism of entry into the class by its members. If inaccurate claims of stimulus generalization are made when training procedures are used in the ostensible generalization conditions, the robustness of the original training procedures will be over estimated. By adhering to the operational requirements of behavioral definitions, we could better understand the power and limits of our educational and training procedures.     

Stimulus and response repetition effects in the detection of sounds: evidence of obligatory retrieval and use of a prior event

Three experiments were performed to examine the extent to which the time required to detect a probe sound is determined by the acoustic characteristics of a preceding prime sound and by the nature of the response made to the prime. The results of Experiment 1 revealed that the effect of frequency repetition was facilitative when a response was made to the occurrence of both the prime and the probe, but was inhibitory when a response was made only to the probe. In contrast, there was no significant effect of location repetition when responses were made to both prime and probe but there was a strongly inhibitory effect when a response was required only to the probe. These results suggest that the acoustic characteristics of the prime along with information about any response made to it, are used in preparing and executing a response to the probe. Experiment 2 was designed to disrupt the temporal link between prime and probe as a way to discourage such retrieval. The results of the experiment revealed that although a response was required to both the prime and probe, no significant effect of frequency repetition was apparent but a robust inhibitory effect of location repetition emerged. In the third experiment repetition effects both within a trial (i.e., prime to probe) and between trials (i.e., probe to prime) were examined. A facilitative effect of frequency repetition was apparent when the interval between sounds was brief, and an inhibitory effect of location repetition was apparent when the interval between sounds was relatively lengthy. Taken together these results suggest that even simple perceptual judgments may be influenced by retrieval of information about a previous processing episode and that effects of frequency repetition and location repetition may be mediated by different mechanisms.     

Spatial modulation of repetition blindness and repetition deafness

When two identical visual items are presented in rapid succession, people often fail to report the second instance when trying to recall both (e.g., Kanwisher, 1987). We investigated whether this temporal processing deficit is modulated by the spatial separation between the repeated stimuli within both audition and vision. In Experiment 1, lists of one to three digits were rapidly presented from loudspeaker cones arranged in a semicircle around the participant. Recall accuracy was lower when repeated digits were presented from different positions rather than from the same position, as compared to unrepeated control pairs, demonstrating that auditory repetition deafness (RD) is modulated by the spatial displacement between repeated items. A similar spatial modulation of visual repetition blindness (RB) was reported when pairs of masked letters were presented visually from either the same or different positions arranged on a semicircle around fixation (Experiment 2). These results cannot easily be accounted for by the token individuation hypothesis of RB (Kanwisher, 1987; Park & Kanwisher, 1994) and instead support a recognition failure account (Hochhaus & Johnston, 1996; Luo & Caramazza, 1995, 1996).     

The repetition effect in judgments of temporal duration across minutes, days, and months.

Three experiments assessed the stability of the repetition effect in time judgment. In Experiment 1, subjects (N = 18) produced intervals ranging from 8 to 31 sec in a two-phase procedure with a five min rest between phases. In Experiment 2, subjects (N = 20) made verbal estimates of intervals ranging from 8 to 20 sec with a 48-hour delay between phases. Experiment 3 involved daily productions by three subjects of intervals ranging from 8 to 54 sec over several months. The slope of the psychophysical function increased across phases in Experimental 1, declined (as expected for estimation) across days in Experiment 2, and increased across months in Experiment 3. It was concluded that the repetition effect is relatively permanent and thus more similar to habituation than to sensory adaptation.     

Derealization and repetition

The psycho-technique of "derealization" helped the majority of the German population that had been loyal to the Hitler regime to escape from their historical responsibility in 1945. The derealization of an historical era of collective history and of the corresponding phases of their individual histories saved these people the work of self transformation and opened the way to an unwitting repetition. In the unending debates around Nazi war criminal and their accomplices, the paramount issue is to refuse the "normality" of this derealization.