Emergent simple discrimination in children: Transfer of stimulus control under non-reinforced conditions

Previous research on humans suggests that simple discriminations may emerge if both stimuli, B1 and B2, are compounded with the stimuli of a previously trained discrimination, A1 (S+) and A2 (S-), and responding to the compounds, B1A1 and B2A2, is reinforced. Two questions were addressed. First, do simple discriminations also emerge if (a) only one stimulus, B1, is compounded with a training stimulus, A1 (S+) or A2 (S-); or with both training stimuli, A1 (S+) and A2 (S-); and (b) neither B1 nor B2 is compounded with the training stimuli? Second, do simple discriminations emerge if reinforcement in the presence of the AB compounds is withheld? Normal preschool children served as subjects. The study consisted of six experiments. Transfer occurred in all experiments regardless of whether both test stimuli, one test stimulus, or none of the test stimuli were compounded with the training stimuli under non-reinforced conditions. The results can be described by the following rules: Respond to any stimulus that includes a component of a “correct” stimulus of a previous discrimination. Otherwise, respond away from the stimulus that incorporates a component from an “incorrect” stimulus of a previous discrimination. The implications of data for sensory pre-conditioning and language-based accounts are discussed.     

Dual coding under conditions of second stimulus modality uncertainty in successive matching tasks

Subjects matched successively presented stimuli within and across modalities. In conditions in which they were informed of the modalities of the two stimuli, no differences in matching performance were obtained between the four types of match (visual-visual, auditory-auditory, visual-auditory, and auditory-visual). Thus, there appeared to be no difference between the modalities in ability to perceive or retain the particular stimuli used. In conditions in which subjects were informed of the modality of the first stimulus but only of the modality in which the second stimulus would appear on 80% of trials, there was again no significant difference between auditory-auditory and visual-visual matching. However, auditory-visual matching was much faster than visual-auditory matching when the second stimulus appeared in the unexpected modality. The results suggest that subjects prepare for both possible types of match when uncertain of the second stimulus modality and that the cross-modal asymmetry reflects the additional attentional load that this incurs.     

Formation of arbitrary stimulus classes in matching to complex samples: supplementary data.

A follow-up study of work published in 1990 showed that consistent use of Tone-relevant trials during training and testing baselines contributed to the reliable formation of 5-member stimulus classes during matching to sample. With Tone-irrelevant trials during either training or testing 4 of 12 subjects formed such classes, but none did so when such trials were used in both training and testing baselines. This extends our prior work.     

Assessing control by elements of complex stimuli in delayed matching to sample.

A series of six experiments examined delayed identity matching-to-sample performances of subjects with mental retardation. The stimuli were either one or two simultaneously displayed forms. When the reinforcement contingencies required that only one form exert discriminative control, all subjects achieved high accuracy scores. However, accuracy scores were substantially lower when the contingencies required discriminative control by two forms, suggesting restricted stimulus control. The decline in matching accuracy appeared to reflect selective losses of conditional control by sample stimuli and shifts in control to features of the comparison stimulus displays. The experiments suggest improved techniques for assessing control by complex stimuli and for evaluating the effects of procedures that seek to broaden restricted stimulus control. The results challenge interpretations based on stimulus-generalization decrement or shared attention.     

The underestimation of egocentric distance: evidence from frontal matching tasks

There is controversy over the existence, nature, and cause of error in egocentric distance judgments. One proposal is that the systematic biases often found in explicit judgments of egocentric distance along the ground may be related to recently observed biases in the perceived declination of gaze (Durgin & Li, Attention, Perception, & Psychophysics, in press), To measure perceived egocentric distance nonverbally, observers in a field were asked to position themselves so that their distance from one of two experimenters was equal to the frontal distance between the experimenters. Observers placed themselves too far away, consistent with egocentric distance underestimation. A similar experiment was conducted with vertical frontal extents. Both experiments were replicated in panoramic virtual reality. Perceived egocentric distance was quantitatively consistent with angular bias in perceived gaze declination (1.5 gain). Finally, an exocentric distance-matching task was contrasted with a variant of the egocentric matching task. The egocentric matching data approximate a constant compression of perceived egocentric distance with a power function exponent of nearly 1; exocentric matches had an exponent of about 0.67. The divergent pattern between egocentric and exocentric matches suggests that they depend on different visual cues.     

Sex differences in unfamiliar face identification: evidence from matching tasks

Research on sex differences in face recognition has reported mixed results, on balance suggesting an advantage for female observers. However, it is not clear whether this advantage is specific to face processing or reflects a more general superiority effect in episodic memory. The current study therefore examined sex differences with a face-matching task that eliminates memory demands. Across two experiments, female but not male observers showed an own-sex advantage on match trials, in which two pictures have to be identified as the same person. This advantage was present for whole faces and when only the internal or external facial features were shown. Female observers were also more accurate in these three conditions on mismatch encounters, in which two photographs have to be identified as different people, but this reflects a more general effect that is present for male and female faces. These findings converge with claims of a female advantage in face recognition and demonstrate that this effect persists when memory demands are eliminated.     

Emergent conditional discrimination in children: Matching to compound stimuli

This study reports two experiments that first taught preschool children identity-matching to compound sample and compound comparison stimuli. A compound stimulus consisted of a colour and a form superimposed on one another. Test sessions assessed whether children related the form and colour elements of a particular compound stimulus. The test for this was matching to sample in which an arbitrary conditional discrimination was required. A majority of the children selected the correct colour comparison in the presence of each form sample. The children also showed the reverse sample-comparison relations: they matched form comparisons to the corresponding colour samples, respectively. In the context of these arbitrary relations, new colours were paired with the form elements of the samples (Experiment 1), and new form elements were paired with the colour elements of the comparisons (Experiment 2). Subsequent tests assessed whether the new stimulus elements had control over responding when presented as single samples or comparisons. Test results showed that most subjects were able to relate the new stimulus elements to the corresponding colour and form elements, respectively. The study demonstrated that matching to compound stimuli in training and testing conditionsMaygenerate conditional relations between the individual stimulus elements.     

Learning with arbitrary versus ecological conditioned stimuli: Evidence from sexual conditioning

Laboratory investigations of Pavlovian conditioning typically involve the association of an arbitrary conditioned stimulus (CS) with an unconditioned stimulus (US) that has no inherent relation to the CS. However, arbitrary CSs are unlikely to become conditioned outside the laboratory, because they do not occur often enough with the US to result in an association. Learning under natural circumstances is likely only if the CS has a preexisting relation to the US. Recent studies of sexual conditioning have shown that in contrast to an arbitrary CS, an ecologically relevant CS is resistant to blocking, extinction, and increases in the CS-US interval and results in sensitized responding and stronger second-order conditioning. Although the mechanisms of these effects are not fully understood, these findings have shown that signature learning phenomena are significantly altered when the kinds of stimuli that are likely to become conditioned under natural circumstances are used. The implications of these findings for an ecological approach to the study of learning are discussed.     

Performance gains from directed training do not transfer to untrained tasks

Given the increasing complexity of the tasks and skills needed in modern society, developing effective training strategies is of tremendous practical importance. Furthermore, training that improves performance of both trained and untrained tasks would be highly efficient. In the present study, we examined how directed training contributes to skill acquisition, and more importantly, to engendering transfer of training to untrained tasks. Participants learned a complex video game for 30 h (Space Fortress, Donchin, Fabiani, & Sanders, 1989) using one of two training regimens: Hybrid Variable-Priority Training (HVT), with a focus on improving specific skills and managing task priority, or Full Emphasis Training (FET) in which participants simply practiced the game to obtain the highest overall score. We compared game performance, retention of training gains, and transfer of training to untrained tasks as a function of the training regimen. Compared to FET, HVT learners reached higher levels of mastery on the game and HVT was particularly beneficial for initially poor performing participants. This benefit persisted seven months after training. However, contrary to expectation, both HVT and FET were unsuccessful in producing transfer to untrained tasks compared to a group that received limited game experience, suggesting that directed training and practice can produce task-specific improvements, but improvements do not necessarily transfer from trained to untrained tasks.     

Detection theory analysis of scaling and discrimination tasks: responses to noxious thermal stimuli

This study's main purpose was to examine the sensitivity estimates obtained from scaling and discrimination approaches for nociception assessment in healthy individuals. This investigation may inform future applications in diagnostic procedures for painful conditions. Models of psychophysical judgment based on those of Durlach and Braida (1969), Laming (1984), and Irwin and Whitehead (1991) were used as the common analytical framework. Noxious thermal contact stimuli were used. The results show that the scaling approach produced lower detection theory sensitivity estimates than did the discrimination approach. The additional judgment variance in scaling tasks could explain this lowered sensitivity. The relative judgmental variance value of 2.18 obtained in this study is lower than variance values found i n previous investigations. This discrepancy i s probably due to the relatively smaller stimulus range employed in this study. The authors propose that the theoretical framework used in this study may be used in future studies to investigate the different dimensions of pain perception.     

Components representation of negative numbers: evidence from auditory stimuli detection and number classification tasks

Past research suggested that negative numbers could be represented in terms of their components in the visual modality. The present study examined the processing of negative numbers in the auditory modality and whether it is affected by context. Experiment 1 employed a stimuli detection task where only negative numbers were presented binaurally. Experiment 2 employed the same task, but both positive and negative numbers were mixed as cues. A reverse attentional spatial-numerical association of response codes (SNARC) effect for negative numbers was obtained in these two experiments. Experiment 3 employed a number classification task where only negative numbers were presented binaurally. Experiment 4 employed the same task, but both positive and negative numbers were mixed. A reverse SNARC effect for negative numbers was obtained in these two experiments. These findings suggest that negative numbers in the auditory modality are generated from the set of positive numbers, thus supporting a components representation.     

Components representation of negative numbers: Evidence from auditory stimuli detection and number classification tasks

Past research suggested that negative numbers could be represented in terms of their components in the visual modality. The present study examined the processing of negative numbers in the auditory modality and whether it is affected by context. Experiment 1 employed a stimuli detection task where only negative numbers were presented binaurally. Experiment 2 employed the same task, but both positive and negative numbers were mixed as cues. A reverse attentional spatial–numerical association of response codes (SNARC) effect for negative numbers was obtained in these two experiments. Experiment 3 employed a number classification task where only negative numbers were presented binaurally. Experiment 4 employed the same task, but both positive and negative numbers were mixed. A reverse SNARC effect for negative numbers was obtained in these two experiments. These findings suggest that negative numbers in the auditory modality are generated from the set of positive numbers, thus supporting a components representation.     

Interlimb coordination: Learning and transfer under different feedback conditions

The role of intrinsic and extrinsic information feedback in learning a new bimanual coordination pattern was investigated. The pattern required continuous flexion-extension movements of the upper limbs with a 90 ° phase offset. Separate groups practiced the task under one of the following visual feedback conditions: (a) blindfolded (reduced FB group), (b) with normal vision (normal FB group), or (c) with concurrent relative motion information (enhanced FB group). All groups were subjected to three different transfer test conditions at regular intervals during practice. These tests included reduced, normal vision, and enhanced vision conditions. Experiment 1 showed that the group receiving augmented information feedback about its relative motions in real-time produced the required coordination pattern more successfully than the remaining two groups, irrespective of the transfer conditions under which performance was evaluated. Experiment 2 replicated and extended the superiority of the enhanced feedback group during acquisition and retention. Experiment 3 demonstrated that successful transfer to various transfer test conditions was not a result of test-trial effects. Overall, the data suggest that the conditions that optimized performance of the coordination pattern during acquisition also optimized transfer performance.     

Modeling parallelization and flexibility improvements in skill acquisition: from dual tasks to complex dynamic skills

Emerging parallel processing and increased flexibility during the acquisition of cognitive skills form a combination that is hard to reconcile with rule-based models that often produce brittle behavior. Rule-based models can exhibit these properties by adhering to 2 principles: that the model gradually learns task-specific rules from instructions and experience, and that bottom-up processing is used whenever possible. In a model of learning perfect time-sharing in dual tasks (Schumacher et al., 2001), speedup learning and bottom-up activation of instructions can explain parallel behavior. In a model of a complex dynamic task (Carnegie Mellon University Aegis Simulation Program [CMU-ASP], Anderson et al., 2004), parallel behavior is explained by the transition from serially organized instructions to rules that are activated by both top-down (goal-driven) and bottom-up (perceptually driven) factors. Parallelism lets the model opportunistically reorder instructions, leading to the gradual emergence of new task strategies.     

Memory for affectively valenced and neutral stimuli in depression: Evidence from a novel matching task

Depressed persons have better memory for affectively negative than positive stimuli, a pattern generally not exhibited by non-depressed individuals. The mechanisms underlying this differential memory are not clear. In this study we examined memory for valenced and neutral stimuli in depressed and non-depressed individuals under conditions of relatively unconstrained encoding. We developed a novel task based on the game, Concentration, in which participants tried to match pairs of positive and negative words, and pairs of neutral words, hidden under squares in as few turns as possible. Whereas non-depressed participants selected and turned over positive squares more frequently than they did negative squares, depressed participants selected and turned over positive and negative squares equally often. Depressed participants also matched fewer positive word pairs within the first five minutes of the task than did non-depressed participants, and they exhibited poorer learning of positive words. Depressed and non-depressed participants did not differ in their matching of neutral words. These findings add to a growing literature indicating that depression is characterised by difficulties in the processing of positive stimuli.     

Memory for affectively valenced and neutral stimuli in depression: evidence from a novel matching task

Depressed persons have better memory for affectively negative than positive stimuli, a pattern generally not exhibited by non-depressed individuals. The mechanisms underlying this differential memory are not clear. In this study we examined memory for valenced and neutral stimuli in depressed and non-depressed individuals under conditions of relatively unconstrained encoding. We developed a novel task based on the game, Concentration, in which participants tried to match pairs of positive and negative words, and pairs of neutral words, hidden under squares in as few turns as possible. Whereas non-depressed participants selected and turned over positive squares more frequently than they did negative squares, depressed participants selected and turned over positive and negative squares equally often. Depressed participants also matched fewer positive word pairs within the first five minutes of the task than did non-depressed participants, and they exhibited poorer learning of positive words. Depressed and non-depressed participants did not differ in their matching of neutral words. These findings add to a growing literature indicating that depression is characterised by difficulties in the processing of positive stimuli.     

Generalizing attentional control across dimensions and tasks: Evidence from transfer of proportion-congruent effects

Three experiments investigated transfer of list-wide proportion congruent (LWPC) effects from a set of congruent and incongruent items with different frequency (inducer task) to a set of congruent and incongruent items with equal frequency (diagnostic task). Experiments 1 and 2 mixed items from horizontal and vertical Simon tasks. Tasks always involved different stimuli that varied on the same dimension (colour) in Experiment 1 and on different dimensions (colour, shape) in Experiment 2. Experiment 3 mixed trials from a manual Simon task with trials from a vocal Stroop task, with colour being the relevant stimulus in both tasks. There were two major results. First, we observed transfer of LWPC effects in Experiments 1 and 3, when tasks shared the relevant dimension, but not in Experiment 2. Second, sequential modulations of congruency effects transferred in Experiment 1 only. Hence, the different transfer patterns suggest that LWPC effects and sequential modulations arise from different mechanisms. Moreover, the observation of transfer supports an account of LWPC effects in terms of list-wide cognitive control, while being at odds with accounts in terms of stimulus–response (contingency) learning and item-specific control.     

Threat-induced impulsivity in Go/Nogo tasks: Relationships to task-relevance of emotional stimuli and virtual proximity

Threatening stimuli are thought to induce impulsive responses, but Emotional Go/Nogo task results are not in line with this. We extend previous research by testing effects of task-relevance of emotional stimuli and virtual proximity. Four studies were performed to test this in healthy college students. When emotional stimuli were task-relevant, threat both increased commission errors and decreased RT, but this was not found when emotional stimuli were task-irrelevant. This was found in both between-subject and within-subject designs. These effects were found using a task version with equal go and nogo rates, but not with 90–10% go-nogo rates. Proximity was found to increase threat-induced speeding, with task-relevant stimuli only, although effects on accuracy were less clear. Threat stimuli can thus induce impulsive responding, but effects depend on features of the task design. The results may be of use in understanding theoretically unexpected results involving threat and impulsivity and designing future studies.