What meaning means for same and different: Analogical reasoning in humans (Homo sapiens), chimpanzees (Pan troglodytes), and rhesus monkeys (Macaca mulatta).

Thus far, language- and token-trained apes (e.g., D. Premack, 1976; R. K. R. Thompson, D. L. Oden, & S. T. Boysen, 1997) have provided the best evidence that nonhuman animals can solve, complete, and construct analogies, thus implicating symbolic representation as the mechanism enabling the phenomenon. In this study, the authors examined the role of stimulus meaning in the analogical reasoning abilities of three different primate species. Humans (Homo sapiens), chimpanzees (Pan troglodytes), and rhesus monkeys (Macaca mulatta) completed the same relational matching-to-sample (RMTS) tasks with both meaningful and nonmeaningful stimuli. This discrimination of relations-between-relations serves as the basis for analogical reasoning. Meaningfulness facilitated the acquisition of analogical matching for human participants, whereas individual differences among the chimpanzees suggest that meaning can either enable or hinder their ability to complete analogies. Rhesus monkeys did not succeed in the RMTS task regardless of stimulus meaning, suggesting that their ability to reason analogically, if present at all, may be dependent on a dimension other than the representational value of stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attenuating verbal overshadowing through color retrieval cues.

Five experiments showed that interference resulting from verbalizing visual stimuli (verbal overshadowing) can be reduced by reintroducing visual cues present at encoding. Object color and background color were used as cues. Participants learned either easy- or hard-to-name figures and then performed an image rotation task. Before performing the imagery task, participants were re-presented with the color patch associated with each figure. Color re-presentation attenuated the impairment associated with easy-to-name stimuli (Experiment 1) as well as labeled hard-to-name stimuli (Experiment 2). However, background color cues had no effect on imagery performance (Experiment 3). Experiment 4 showed that naming the object colors at encoding makes color retrieval cues ineffective. Finally, Experiment 5 showed that object color cues can help participants to overcome previously exhibited impairment resulting from covert verbalization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Why does a red snake in the grass capture your attention?

It has been suggested that affective stimuli automatically capture attention; this preferential processing is thought to be related to the evolutionary significance of affective stimuli. However, recent evidence suggests that perceptual salience alone might explain why some affective stimuli are more likely to influence attentional processes in certain contexts. In this study, we manipulated affective and perceptual salience to better understand how affective information is processed and how it impacts attentional processes in different contexts. We used stimuli that are both affectively and perceptually salient, while varying the task requirement to encourage the processing of perceptually salient (Experiment 1) or affectively salient (Experiment 2) information. This design made it possible to observe independent and interdependent relationships between perceptual and affective salience. The results showed that when the task encouraged the processing of perceptually salient information, affective salience did not influence task performance. In contrast, when the task encouraged the processing of affectively salient information, affectively salient information impaired task performance. The findings suggest that the affective nature of the stimuli does not always influence attentional processes. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Cognitive precedence for local information in hierarchical stimulus processing by pigeons.

Four experiments investigated the processing of hierarchical stimuli by pigeons. Using a 4 alternative divided–attention task, 4 pigeons were food-reinforced for accurately identifying letters arranged as either hierarchical global- or local-relevant stimuli or as size-matched filled stimuli. Experiment 1 found that task acquisition was faster with local-relevant than global-relevant stimuli. This difference was not due to letter size. Experiment 2 demonstrated successful transfer to a novel irrelevant letter configuration. Experiments 3 and 4 tested pigeons' responses to conflict probe stimuli composed of equally discriminable relevant letters at each level. These tests revealed that all of the pigeons showed a cognitive precedence for local information early in processing, with the pigeons using different cues to initiate the processing of global information. This local advantage contrasts with previously reported results for humans and pigeons but is similar to that reported for nonhuman primates. Alternatives attempting to reconcile these contrasting comparative results are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence for task conflict in the Stroop effect.

C. M. MacLeod and P. A. MacDonald (2000) suggested that congruent and incongruent Stroop stimuli cause more task conflict than neutral stimuli because the anterior cingulate cortex is more activated with these stimuli. This study investigated behavioral expression for this pattern. Experiment 1 reduced task conflict control by increasing the proportion of nonword neutrals. Additionally, half the trials had conflict or neutral cues. The control reduction revealed the task conflict. For noncued trials, response time was longer for congruent stimuli than for neutral stimuli (reverse facilitation effect). In addition, response time for congruent stimuli was longer when stimuli were uncued vs. cued. Experiment 2 increased task conflict control by changing the neutral stimuli to noncolor words. Consequently, the task conflict expression disappeared. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of signaling retention interval length on delayed matching-to-sample in pigeons.

Pigeons were trained initially on a delayed matching task in which colors served as sample and comparison stimuli. During subsequent training, additional stimuli compounded with the sample signaled whether that trial involved a short (1 s) or a long (5 s) delay. In Experiment 1, miscuing reduced accuracy at the short delay markedly and tended to increase accuracy at the long delay slightly. Experiments 2 and 3 revealed a robust effect of cuing when the cues followed sample termination, thereby refuting the view that such cues evoke differential attention to the sample stimulus. Experiment 4 revealed that the cues did not influence rate of forgetting, and Experiment 5 revealed no effect of point of cue placement within the retention interval. It was concluded that cues correlated with retention interval length modulated matching accuracy independently of memory, perhaps by signaling different rates of reinforcement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analogical reasoning in a capuchin monkey (Cebus apella).

Previous evidence has suggested that analogical reasoning (recognizing similarities among object relations when the objects themselves are dissimilar) is limited to humans and apes. This study investigated whether capuchin monkeys (Cebus apella) can use analogical reasoning to solve a 3-dimensional search task. The task involved hiding a food item under 1 of 2 or 3 plastic cups of different sizes and then allowing subjects to search for food hidden under the cup of analogous size in their own set of cups. Four monkeys were exposed to a series of relational matching tasks. If subjects reached criterion on these tasks, they were exposed to relational transfer tasks involving novel stimuli. Three of the monkeys failed to reach criterion on the basic relational matching tasks and therefore were not tested further. One monkey, however, revealed above-chance performance on a series of transfer tasks with 3 novel stimuli. This evidence suggests that contrary to previous arguments, a member of a New World monkey species can solve an analogical problem. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Categorical shape and color coding by pigeons.

Two studies with 32 pigeons assessed the categorical coding of shapes and the existence of a higher-order color category (all colors). Ss were trained on 2 independent tasks (matching-to-sample and oddity-from-sample). One task involved red and a plus sign, the other a circle and green. On test trials, 1 of the 2 comparison stimuli from one task was replaced by one of the stimuli from the other task. Differential performance based on which of the 2 stimuli from the other task was introduced suggested categorical coding rules. In Exp I, evidence for the categorical coding of sample shapes was found. Categorical color coding was also found; however, it was the comparison stimuli rather than the samples that were categorically coded. Exp II replicated the categorical shape sample effect and ruled out the possibility that the particular colors used were responsible for the categorical coding of comparison stimuli. Results support the view that pigeons can develop categorical rules involving shapes and colors and that the color categories can be hierarchical. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Time, capacity, and selection between perceptual attributes

Three experiments were run to determine whether time and central-processing capacity are requried to select between perceptual attributes. A same-different matching task was employed for all experiments. In Experiments 1 and 2, three sets of stimulus pairs were used, each of which varied along only one relevant perceptual dimension (color, size, or form). In Experiment 1, reaction time on the matching task was shown to be faster when the stimuli were presented in blocks in which all stimulus pairs came from the same set (blocked presentation) than when stimulus pairs from each of the three sets were randomly intermixed (random presentation). In Experiment 2, reaction time on a secondary probe task was faster during the encoding stage of a sequential mathcing task with blocked presentation than with random presentation. Experiment 3 indicated that this outcome could not be attributed to a difference in the number of possible stimulus alternatives. Thus, the results support the hypothesis that time and central-processing capacity are required to select between perceptual attributes.     

Source memory enhancement for emotional words.

The influence of emotional stimuli on source memory was investigated by using emotionally valenced words. The words were colored blue or yellow (Experiment 1) or surrounded by a blue or yellow frame (Experiment 2). Participants were asked to associate the words with the colors. In both experiments, emotionally valenced words elicited enhanced free recall compared with nonvalenced words; however, recognition memory was not affected. Source memory for the associated color was also enhanced for emotional words, suggesting that even memory for contextual information is benefited by emotional stimuli. This effect was not due to the ease of semantic clustering of emotional words because semantically related words were not associated with enhanced source memory, despite enhanced recall (Experiment 3). It is suggested that enhancement resulted from facilitated arousal or attention, which may act to increase organization processes important for source memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influences of closure, occlusion, and size on the perception of fragmented pictures

Two experiments examined the ability to recognize a repeated figure in stimuli where only fragments of the figures were presented. Fragments were either closed or open regions presented either with or without an occluder that filled the spaces between the fragments (Experiment 1). Recognition performance was significantly better for open fragments, with or without an occluder, contrary to previous assertions that the occluder is the important factor for recognition. When stimulus size was varied, an occluder hindered recognition performance in the smallest size condition relative to unoccluded stimuli, which were equally easy to recognize across all size conditions (Experiment 2). The size results support the idea of size invariance in object naming. The difficulty in the smallest occluded condition is discussed in terms of differences in global and local processing depending on visual angle and sparsity.     

Perceptual effects on remembering: Recollective processes in picture recognition memory.

In 3 experiments, the effects of perceptual manipulations on recollective experience were tested. In Experiment 1, a picture-superiority effect was obtained for overall recognition and Remember judgments in a picture recognition task. In Experiment 2, size changes of pictorial stimuli across study and test reduced recognition memory and Remember judgments. In Experiment 3, deleterious effects of changes in left–right orientation of pictorial stimuli across study and test were obtained for Remember judgments. An alternate framework that emphasizes a distinctiveness–fluency processing distinction is proposed to account for these findings because they cannot easily be accommodated within the existing account of differences in conceptual and perceptual processing for the 2 categories of recollective experience: Remembering and Knowing, respectively (J. M. Gardiner, 1988; S. Rajaram, 1993). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emotional Conditioning to Masked Stimuli and Modulation of Visuospatial Attention.

Two studies investigated the effects of conditioning to masked stimuli on visuospatial attention. During the conditioning phase, masked snakes and spiders were paired with a burst of white noise, or paired with an innocuous tone, in the conditioned stimulus (CS)+ and CS- conditions, respectively. Attentional allocation to the CSs was then assessed with a visual probe task, in which the CSs were presented unmasked (Experiment 1) or both unmasked and masked (Experiment 2), together with fear-irrelevant control stimuli (flowers and mushrooms). In Experiment 1, participants preferentially allocated attention to CS+ relative to control stimuli. Experiment 2 suggested that this attentional bias depended on the perceived aversiveness of the unconditioned stimulus and did not require conscious recognition of the CSs during both acquisition and expression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Phonology can help or hurt the perception of print.

Phonological manipulations affect performance in a letter search task that requires only a shallow level of processing. In Experiment 1, phonology reduced accuracy in the letter search task when a pseudohomophone (GAIM) contained a target letter ("i") that was missing in the spelling of its (nonpresented) sound-alike base word (GAME). In Experiment 2, phonology increased accuracy in the letter search task when the target letter was present in both the spelling of the pseudohomophone and the spelling of its sound-alike base word ("m" in GAIM and GAME). In Experiment 3, we showed that the phonology-hurts effect of Experiment 1 is not peculiar to nonword letter strings but generalizes to familiar words. In Experiment 4, we obtained a phonology-hurts effect on correct response times when stimuli were visible until participants responded (stimuli were not masked). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Absence of perceptual processing during reconfiguration of task set.

The authors manipulated stimulus contrast and response-stimulus interval in the alternating runs paradigm to investigate whether early processing could be carried out during a task switch. Subjects alternated between judging the magnitude and the parity of a digit. The results suggested that early processing was not carried out during the task switch (Experiment 1), even in the absence of potentially confounding auditory or visual warning signals (Experiment 2). This processing was, however, carried out in parallel with a demanding operation in a 2nd task (Experiment 3), using the display parameters of Experiments 1 and 2 in the psychological refractory period paradigm. It is concluded that, functionally, task switching may impose a hard bottleneck even for very early stimulus processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential outcome effects in Pavlovian biconditional and ambiguous occasion setting tasks.

Three experiments with rats explored the differential outcome effect (DOE) using a Pavloian magazine approach conditioning preparation. Experiment 1 compared groups trained on a biconditional discrimination (AX+, AY?, BX?, BY+) with differential or nondifferential outcomes, and Experiment 2 examined this using an ambiguous occasion setting task (e.g., AX+, X?, Y+, AY?). In both experiments, subjects trained with differential outcomes learned the tasks better than subjects trained with nondifferential outcomes. Furthermore, subjects given differential outcome training learned the positive occasion setting component of the ambiguous task more efficiently than the negative occasion setting component, although both were enhanced by differential outcome training. Experiment 3 demonstrated that the ambiguous occasion setting task was reversed more readily when the target–outcome relations (as opposed to the modulator–outcome relations) were maintained during the reversal phase. These data suggest that an acquired distinctiveness effect may be responsible for the DOE in Pavlovian learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Parallel memory retrieval in dual-task situations: I. Semantic memory.

Can participants retrieve information about the 2nd of 2 stimuli while they are processing the 1st? Four experiments suggest they can. Reaction times to the 1st stimulus were faster if it came from the same category as the 2nd than if it came from a different category. This category-match effect was observed for letter-digit discrimination (Experiment 1), magnitude and parity judgments about digits (Experiment 2), and lexical decisions (Experiment 3). Experiment 4 showed that the 2nd stimulus could semantically prime the 1st. The category-match effect was observed only when the same task was performed on the 2 stimuli. When the task changed from the Ist stimulus to the 2nd, there was no advantage of a category match. This dependence on task set may explain previous failures to find parallel retrieval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emergent conditional discriminations in children and adults: stimulus equivalence derived from simple discriminations

This study examines whether trained and derived simple discriminations lead to conditional relations between discriminative stimuli of the same and opposite (S+, S-) functions. After being trained on an arbitrary X-Y task (X1-Y1, X2-Y2) and on two simple discrimination tasks (A1+/A2- and B1+/B2-), children (Experiment 1) and adults (Experiment 2) were tested on the formation of novel simple discriminations (A3+/A2- and B3+/B2-) and conditional stimulus relations between all directly and indirectly paired A stimuli and between all directly and indirectly paired B stimuli (A1-A2-A3, B1-B2-B3). Subjects who formed these sets also received A2-X1 and B1-X2 training followed by a series of probes to assess the formation of two five-member stimulus equivalence classes (A1-A2-A3-X1-Y1, B1-B2-B3-X2-Y2). A modest majority of the children matched the directly paired stimuli (A2-A1, B2-B1 and A1-A2, B1-B2; A2-A3, B2-B3 and A3-A2, B3-B2) with one another while only a few of them also matched the indirectly paired stimuli with one another (A1-A3, B1-B3 and A3-A1, B3-B1). Those who did also related all the A and B stimuli with the designated X and Y stimuli. By contrast, all normal adults matched all paired and conditionally linked stimuli with one another. Present findings and those of related studies on stimulus equivalence are discussed from a stimulus contiguity perspective.     

A prototype effect and categorization of artificial polymorphous stimuli in pigeons

In a go-no-go discrimination task, pigeons were trained to discriminate artificial polymorphous stimuli differing along 3 six-valued features. Exemplars of each category were generated by systematic transformations of the features from a single stimulus, a base pattern (prototype). They were then tested for transfer to novel stimuli including the base patterns. The most pronounced discrimination occurred between the base patterns rather than between the extreme positive and negative stimuli. A distance-from-prototype rule and an additive integration of feature utilities or of feature frequencies are suggested to account for the prototype effect. In Experiment 2, pigeons were trained on a 2-key choice discrimination task, with the base patterns as conditional stimuli. Subsequent testing with distorted stimuli suggested that a distance-from-prototype model best explains the present findings.     

Discrimination and generalization along a simple dimension: Peak shift and rule-governed responding.

In 2 experiments, participants learned to discriminate between a pair of simply related, but very similar, colors in a 2-choice categorization task. They were then tested over a wider range of isoluminant hues. Over these test values, both experiments yielded a postdiscrimination gradient that was initially peak-shifted but became monotonic through the course of testing. In Experiment 2, the presence of this early peak shift and subsequent change in gradient form were related to participants’ inability to verbally characterize the difference between the training stimuli. This suggests a transition from generalization based on simple physical similarity to generalization based on a “verbalizable” rule, as a consequence of additional relevant information becoming available during test. An explanation appealing to both associative and strategically controlled verbal processes provides an accurate account of the results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)