Transfer of matching-to-sample in pigeons

In Experiment I, pigeons were first trained on simultaneous matching-to-sample with either color stimuli or form stimuli, and then shifted to stimuli on the other dimension. Matching performance in the first session with stimuli on a given dimension was not affected by prior matching training with stimuli on the other dimension. However, in the first six color-matching sessions pooled, birds with prior form-matching training performed significantly better than birds without any prior matching training. In Experiment II, birds with experience matching both colors and forms in separate sessions were tested with novel stimulus configurations involving either novel stimuli or novel combinations of familiar colors and forms. Matching performance was not affected by novel stimulus configurations, except that performance dropped to a chance level or below when the standard stimulus was novel. In Experiments II, III, and IV, three of four tests did not show any effect of prior reinforcement of pecks at a novel stimulus, presented alone, on subsequent matching of that stimulus. The results were interpreted as indicating that matching performance in pigeons depends on the learning of stimulus-response chains involving the specific stimuli employed during training. An incidental observation in Experiments I and II was that there were typically more excess pecks at the standard stimulus during form-matching sessions than during color-matching sessions, which may be related to the fact that form matching is more difficult than color matching.     

Recall cued by selectively attended and unattended attributes

Three experiments were carried out to investigate the effects upon subsequent recall of categorizing a stimulus at presentation by one of its attributes. The results indicated that a previously reported finding of categorized cue superiority for integral stimuli in an incidental learning paradigm may not be a robust one. Two experiments employed either intentional or incidental learning paradigms. In both, attributes that had been categorized at presentation did not differ in effectiveness as subsequent recall cues from those that had not. In a third experiment, with incidental learning, categorized cues were less effective than uncategorized cues. Thus, observed effects of categorization appear to be sensitive to minor differences in experimental procedure between studies.     

Display reinforcement in the Siamese fighting fish, Betta splendens: aggressive motivation or curiosity?

Fish were tested in a runway T-maze apparatus. The experiments compared performance (measured by swimming speed and percent choice correct) to a variety of stimuli in the goal box. The stimulus that evoked the most vigorous aggressive display (a live conspecific) supported the highest level of performance; a stimulus that evoked no display (a marble) failed to sustain operant behavior. Stimuli that induced some aggression, but also some escape (live nondisplaying fish), supported performance at reduced levels. These results implicate aggression and not curiosity as the primary motivating factor. They also show that the responsiveness of the stimulus is a critical aspect of reinforcement and that the level of performance is determined by escape tendencies as well as aggression. It is proposed that failure of a stimulus to provide appropriate feedback constitutes an aversive event.     

ACQUISITION OF SIGN LANGUAGE BY AUTISTIC CHILDREN II: SPONTANEITY AND GENERALIZATION EFFECTS

Autistic children typically do not use their language repertoire in order to communicate. Six autistic children who exhibited poor communication skills were trained to use their sign repertoire to make spontaneous requests of adults. Training consisted of imitative prompting, fading, and differential reinforcement, and included aspects of incidental teaching. The children displayed an increase in the rate and variety of spontaneous sign requests (Experiment 1). Generalization of spontaneity across adults (Experiments 1 and 2) and settings (Experiment 2) was also observed. We suggest that spontaneity may be facilitated when language is brought under the control of broadly defined stimuli such as adult attention rather than narrowly defined stimuli such as the presence of specific objects or verbal prompting in the form of questions. Finally, response generalization was observed as well (Experiment 1). Specifically, as spontaneity increased, self-stimulatory behavior decreased. This result may be accounted for in terms of reinforcer competition, reinforcer consistency, or discriminative stimulus effects.     

Stimulus and response chunking in the Hebb Digits task

Using the Hebb Digits task, an incidental sequential learning paradigm, the effects of chunking of both the presentation and response phases of performance were examined. In the first experiment, consistent stimulus chunking increased learning, and performance was at an equivalent level to this when consistent chunking of both stimuli and responses was present. Consistent chunking of the responses alone did not significantly improve learning over a baseline condition where neither stimuli nor responses were chunked. The disruption of response organization in a second experiment, through a random response condition, failed to impact learning in non-chunked and stimulus chunked conditions. A third experiment found that response chunking did benefit learning in a condition where stimuli were presented in random chunks. A final experiment suggested extended processing of the digits could not account for performance gains in the stimulus chunking condition. Overall, the results suggest that the enhanced effects of chunking on learning were stimulus-driven rather than response-driven, except under conditions that constrained a consistent pattern of stimulus organization.     

Eye movements as a gatekeeper for memorization: evidence for the persistence of attentional sets in visual memory search

Attention is known to serve multiple goals, including the selection of information for further perceptual analysis (selection for perception) and for goal-directed behavior (selection for action). Here, we study the role of overt attention (i.e., eye movements) as a gatekeeper for memorization processes (selection for memorization). Subjects memorized complex multidimensional stimulus displays and subsequently indicated whether a specific (probe) item was present. In Experiment 1 we utilized an incidental learning setting where in the beginning only a subset of display stimuli was relevant, whereas in a transfer block all stimuli were possible probe items. In Experiment 2, we used an explicit learning setting within a between-group design. Response times and gaze patterns indicated that subjects learned to ignore irrelevant stimuli while forming memory representations. The findings suggest that complex feature binding processes in peripheral vision may serve to guide overt selective attention, which eventually contributes to filtering out irrelevant information even in highly complex environments. Gaze patterns suggested that attentional control settings persisted even when they were no longer required.     

The biological function of Pavlovian conditioning: Learned inhibition of aggressive behavior in territorial fish

Following Pavlovian discrimination training, stimuli predicting the appearance of a territory intruder (an excitatory conditional stimulus, CS+) or the absence of that event (an inhibitory conditional stimulus, CS−) were presented to pairs of territorial male fish immediately before their first aggressive interaction. Pairmates that both received excitatory stimuli prior to the confrontation were significantly more aggressive than a control group which received the same training but which received neither a CS+ nor a CS− in the test. Pairmates in which both received a CS− were significantly less aggressive than the control group. In these three groups, no differences in aggression were observed between the individual members of a single pair. Two additional groups were composed of pairs whose members received different stimuli prior to the test. Although no differences were found between pairmates in the group in which one member received a pretest CS− while the other member received no stimulus presentation, large differences in aggressive behavior were obtained when one fish received a CS+ and its pairmate received a CS−. We discuss the behavioral ecology of terriorial behavior in fish and attempt to show the potential importance of these results in this naturalistic context. In addition, we discuss the implications of an ecological approach for causal analyses of inhibitory learning.     

The origin of exemplar effects in rule-driven categorization

S. W. Allen and L. R. Brooks (1991) have shown that exemplar memory can affect categorization even when participants are provided with a classification rule. G. Regehr and L. R. Brooks (1993) argued that stimuli must be individuated for such effects to occur. In this study, the authors further analyze the conditions that yield exemplar effects in this rule application paradigm. The results of Experiments 1-3 show that interchangeable attributes, which are not part of the rule, influence categorization only when attention is explicitly drawn on them. Experiment 4 shows that exemplar effects can occur in an incidental learning condition, whether stimulus individuation is preserved or not. The authors conclude that the influence of exemplar learning in rule-driven categorization stems from the attributes specified in the rule or in the instructions, not from the stimulus gestalts.     

Symmetry in haptic and in visual shape perception

Four experiments tested the hypothesis that bilateral symmetry is an incidental encoding property in vision, but can also be elicited as an incidental effect in touch, provided that sufficient spatial reference information is available initially for haptic inputs to be organized spatially. Experiment 1 showed that symmetry facilitated processing in vision, even though the task required judgments of stimulus closure rather than the detection of symmetry. The same task and stimuli failed to show symmetry effects in tactual scanning by one finger (Experiment 2). Experiment 3 found facilitating effects for vertically symmetric open stimuli, although not for closed patterns, in two-forefinger exploration when the fore-fingers had previously been aligned to the body midaxis to provide body-centered spatial reference. The one-finger exploration condition again failed to show symmetry effects. Experiment 4 replicated the facilitating effects of symmetry for open symmetric shapes in tactual exploration by the two (previously aligned) forefingers. Closed shapes again showed no effect. Spatial-reference information, finger movements, and stimulus factors in shape perception by touch are discussed.     

Autonomic conditioning to monetary and social stimuli and aggression in children

Poor conditioning to punishment, such as loud tones or electric shock, has been proposed as an important factor involved in the etiology of aggressive and psychopathic behavior. However, it is not known whether the association holds when monetary or social stimulus is used as the unconditioned stimulus, and if aggressive individuals also have impaired conditioning to rewards. In this study, skin conductance responses in a conditioning task involving both monetary/social reward and punishment as unconditioned stimuli were assessed in 340 male and female 8‐ to 9‐year‐old children from the community. Children reported their reactive and proactive aggression using the Reactive and Proactive Aggression Questionnaire (RPQ; Raine et al., 2006). Results showed that monetary/social reward and punishment were effective in eliciting physiological classical conditioning in children, and that reduced reward conditioning was associated with high levels of proactive aggression in particular. Findings highlight the importance of distinguishing between reactive and proactive aggression when examining antisocial behavior in children, and suggest that reward‐oriented treatment programs may not be effective for children with more proactive, instrumental aggressive behavior.

     

Taking a bright view of negative priming in the light of dim stimuli: further evidence for memory confusion during episodic retrieval.

A same-different letter-matching task was used to examine the effects of stimulus intensity on negative priming, which is poorer performance when target letters have been presented as distractor letters on the immediately preceding trial. In Experiment 1, stimulus intensity was manipulated between-participants, whereas in Experiment 2, it varied randomly from trial-to-trial within-participants. In Experiment 1, negative priming was equivalent for both stimulus intensities. In Experiment 2, negative priming effects were larger for repeated intensity stimuli than for nonrepeated intensity stimuli, when stimulus intensity was dim. Furthermore, for repeated intensity stimuli, negative priming effects were enhanced when the overt response required to the stimulus was repeated from prime to probe trial. These results are consistent with the hypothesis that negative priming may be due to memory confusion, rather than to inhibition of the distractor stimuli.     

Children's selective attention with variation in amount of stimulus exposure

Selective attention in children was measured by means of a central-incidental learning paradigm. Children performed a central task requiring attention to one element in each of several stimuli, after which their incidental learning was assessed by a combination of two tests measuring: (a) recognition of the second, or incidental, element in each stimulus, and (b) association between the incidental and central elements. Principal independent variables were the age of the children (9 vs 12 years) and the amount of exposure time per trial in the central task (6 vs 12 sec). Douling the exposure time increased the incidental as well as the central scores for 9-year-olds, while it increased only the central scores for 12-year-olds. It would appear that younger children maintain a relatively nonselective orientation during an extended exposure period, distributing attention between both relevant and irrelevant stimulus elements, whereas adolescents adopt a more selective approach and concentrate exclusively on task-relevant information. The results are discussed in relation to hypotheses regarding development of selective attention.     

The discrimination of relative frequency by pigeons.

Five experiments addressed the issue of how pigeons learn to discriminate the relative frequency of stimuli. During a sampling period, three different stimuli (keylights) were presented serially, in mixed order, and with different frequencies. During a choice period, the stimuli were presented simultaneously, and reinforcement was arranged for choosing the stimulus that was presented the least number of times during the sample. The results showed that (a) the overall proportion of correct choices was always above chance levels; (b) the likelihood of a correct choice decreased with the serial position of the correct stimulus, a negative recency effect; (c) when the last three stimuli of the sample were constrained to be one of each kind, the negative recency effect decreased but errors became more likely when the correct stimulus occurred early in the sample, a negative primacy effect; (d) accurate performance generalized to new and larger samples; and (e) under some conditions the probability of a correct choice was independent of the serial position of the correct stimulus. The serial position curves suggest that in a least frequent discrimination task, two processes determine how the least frequent stimulus controls behavior: a passive decay process (the stimulus loses its effectiveness with time since its last occurrence), and a residual salience process (when the stimulus occurs in the first position it may decay to a higher asymptote than when it occurs in later positions.     

Incidental task sequence learning: perceptual rather than conceptual?

In four experiments we investigated whether incidental task sequence learning occurs when no instructional task cues are available (i.e. with univalent stimuli). We manipulated task sequence by presenting three simple binary-choice tasks (colour, form or letter case decisions) in regular repeated or random order. Participants were required to use the same two response keys for each of the tasks. We manipulated response sequence by ordering the stimuli so as to produce either a regular or a random order of left versus right-hand key presses. When sequencing in both, or either, separate stream (i.e. task sequence and/or response sequence) was changed to random, only those participants who had processed both sequences together showed evidence of sequence learning in terms of significant response time disruption (Experiments 1-3). This effect disappeared when the sequences were uncorrelated (Experiment 4). The results indicate that only the correlated integration of task sequence and response sequence produced a reliable incidental learning effect. As this effect depends on the predictable ordering of stimulus categories, it suggests that task sequence learning is perceptual rather than conceptual in nature.     

How meaning shapes seeing

Inattentional blindness refers to the failure to see an unexpected object that one may be looking at directly when one's attention is elsewhere. We studied whether a stimulus whose meaning is relevant to the attentional goals of the observer will capture attention and escape inattentional blindness. The results showed that an unexpected stimulus belonging to the attended semantic category but not sharing physical features with the attended stimuli was detected more often than a semantically unrelated stimulus. This effect was larger when the unexpected stimuli were words than when they were pictures. The results imply that the semantic relation between the observer's attentional set and the unexpected stimulus plays a crucial role in inattentional blindness: An unexpected stimulus semantically related to the observer's current interests is likely to be seen, whereas unrelated unexpected stimuli are unseen. Attentional selection may thus be driven by purely semantic features: Meaning may determine whether or not one sees a stimulus.     

Reducing the saliency of intentional stimuli results in greater contextual-dependent performance

Wright and Shea (1991) described intentional stimuli as explicitly identified information necessary to successfully perform a task, whereas incidental stimuli are not explicitly identified as crucial to task performance but have the potential to become associated with particular responses because of their selective presence in the training environment. Shea and Wright (1995), using a speeded-choice RT task, indicated that manipulating the strength of association between incidental information and the responses, by changing the discriminability of incidental stimuli while fixing the strength of the association between the intentional stimuli and each response, had a significant impact on task performance. The present experiment further examined the role played by incidental stimuli when the strength of association between the intentional stimuli and the associated responses was reduced, by minimising stimulus-response compatibility. It was assumed that this latter manipulation would have a similar impact as increasing the strength of incidental stimuli-response relationships. That is, the relative contribution of the incidental stimuli would increase, resulting in an increase in context-dependent behaviour during tests in which the intentional and incidental stimuli activated different responses. The results were in agreement with this prediction and consistent with a model for contextual-dependent performance proposed by Shea and Wright (1995) as well as with the outshining hypothesis forwarded by Smith (1988, 1994).     

The evolutionary significance of habituation and sensitization across phylogeny: A behavioral homeostasis model

The phenomenon of habituation may be interpreted as a process that has evolved for filtering out iterative stimuli of little present relevance. That habituation is seen in aneural as well as neural organisms throughout phylogeny with remarkably similar characteristics suggests that its role is an important one in animal survival. If habituation is to be viewed as a process to filter out iterative stimuli that have no significant consequences, then how is sensitization to be viewed? One way of viewing these two behavioral changes, i.e. habituation and sensitization, is that they are homeostatic processes which optimize an organism’s likelihood of detecting and assessing the significance of a stimulus in a new iterative series or a change in it. If one views the level of initial responsiveness to a new stimulus as a function of an organism’s threshold just prior to stimulus occurrence, then “high responders” (i.e. those who initially react more strongly) are assumed to have a lower threshold for detecting and assessing the significance of this stimulus than are the “low responders” (i.e. those who initially react more weakly). Thus, high-responders would initially receive more sensory input and progressively decrease their responsiveness to a non-threatening stimulus (habituation). Likewise, initial low-responders would receive less sensory input followed by a decreased threshold and an increased response to the next stimulus occurrence (sensitization). The level of responsiveness achieved in both habituaters and sensitizers, as an asymptote is approached, is a balance between being too sensitive to an unimportant stimulus (and possibly missing other significant stimuli) and being too insensitive, and missing a change in the relevance of the present stimulus. These response changes can be taken as indices of the organism’s mechanisms for achieving an appropriate threshold level to an iterative stimulus in order to accurately assess its present significance and then eventually to asymptote at an optimal stable response level. This approach toward an asymptote is a behavioral homeostatic process that reflects the accumulated significance of the iterative stimulus at each occurrence. The purpose of adding “behavioral” to the term “homeostasis” is to extend the usual meaning of the concept from primarily internal processes to also include (a) iterative external stimulation, (b) the organism’s initial threshold to the initial stimulus as well as (c) the behavior which results from it. Since we are discussing organisms that range from intact, single-celled protozoa to intact mammals, as well as surgically simplified preparations, the termsstimulus, response andbehavior will be used broadly. While other investigators have focused on specific cellular mechanisms underlying habituation and sensitization in a given organism, this paper focuses on the adaptive significance of these two behavioral processes viewed across phylogeny.     

Influence of contextual information on observers' perceptions of actors' intentions to harm others

Previous examinations of perceptions of aggressive behaviors have used static stimulus presentations (e.g., photographs or slides). This investigation examined the impact of varying amounts of geographical and temporal contextual information on observers' perceptions of actors' intentions to physically and psychologically (intimidate) harm others. Participants (51 elite ice hockey players) were randomly assigned to view one of three video-taped presentations showing eight ice hockey behaviors in either a) a dynamic mode with contextual information, b) a dynamic mode with no context, or c) a static, “freeze-frame” mode. MANOVA results showed that non-aggressive stimuli were perceived as less aggressive, and aggressive stimuli were perceived as more aggressive in dynamic presentations with context than in static presentations. Based on these findings, it is suggested that future research focussing on perceptions of aggressive behavior utilize a dynamic stimulus presentation containing context material. © 1996 Wiley-Liss, Inc.     

Naturalistic psychophysics: thresholds of ducklings (Anas platyrynchos) and chicks (Gallus gallus) to tones that resemble mallard calls

Neonatal ducklings and chickens were tested for responsiveness to a pulsing pure tone that was as similar as possible to the mallard maternal alarm call. It is known that ducklings momentarily cease vocalizing when they hear the alarm call and that chicks do the same when they hear pure tones. The duration of peep suppression can thus be used as a measure of whether subjects of either species heard the stimulus. Chicks might not be as sensitive as ducklings to a mallard alarm call because the signal is less significant to them. An adaptive or staircase procedure was used to estimate absolute thresholds, and group psychometric functions were reconstructed for each species from the trial-by-trial data. Ducklings had lower thresholds than chickens as well as steeper psychometric functions to this stimulus. The results suggest that more sensitive and consistent behavioral responses can be elicited by naturalistic sounds than by more arbitrary acoustic stimuli.     

Enhancing the effects of extinction on attention-maintained behavior through noncontingent delivery of attention or stimuli identified via a competing stimulus assessment

Recent research has shown that the noncontingent delivery of competing stimuli can effectively reduce rates of destructive behavior maintained by social-positive reinforcement, even when the contingency for destructive behavior remains intact. It may be useful, therefore, to have a systematic means for predicting which reinforcers do and do not compete successfully with the reinforcer that is maintaining destructive behavior. In the present study, we conducted a brief competing stimulus assessment in which noncontingent access to a variety of tangible stimuli (one toy per trial) was superimposed on a fixed-ratio 1 schedule of attention for destructive behavior for individuals whose behavior was found to be reinforced by attention during a functional analysis. Tangible stimuli that resulted in the lowest rates of destructive behavior and highest percentages of engagement during the competing stimulus assessment were subsequently used in a noncontingent tangible items plus extinction treatment package and were compared to noncontingent attention plus extinction and extinction alone. Results indicated that both treatments resulted in greater reductions in the target behavior than did extinction alone and suggested that the competing stimulus assessment may be helpful in predicting stimuli that can enhance the effects of extinction when noncontingent attention is unavailable. DESCRIPTORS: Attention-maintained problem behavior, competing stimuli, extinction, functional analysis, noncontingent reinforcement