Motor response programming during simple choice reaction time: The role of practice.

Reaction time (RT) before a motor response has been shown to depend on the duration or complexity of the response, indicating that responses may be programmed during RT. Some studies have reported that choice RT is influenced more than simple RT when these parameters are varied; other studies report the opposite pattern with a stronger relation for simple RT than for choice RT. The present experiments resolved this apparent discrepancy in the literature by demonstrating that the predominant effect was on choice RT when the duration of a single response component was varied and that the predominate effect was on simple RT when the number of components in a response sequence was varied. This relation for simple RT was eliminated with practice, possibly because participants learned to recode multiple-component responses into a single chunk. A two-process view of response programming seems to be necessary to account for the findings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociations between reaction times and temporal order judgments: A diffusion model approach.

A diffusion model for simple reaction time (RT) and temporal order judgment (TOJ) tasks was developed to account for a commonly observed dissociation between these 2 tasks: Most stimulus manipulations (e.g., intensity) have larger effects in RT tasks than in TOJ tasks. The model assumes that a detection criterion determines the level of sensory evidence needed to conclude that a stimulus has been presented. Analysis of the performance that would be achieved with different possible criterion settings revealed that performance was optimal with a lower criterion setting for the TOJ task than for the RT task. In addition, the model predicts that effects of stimulus manipulations should increase with the size of the detection criterion. Thus, the model suggests that commonly observed dissociations between RT and TOJ tasks may simply be due to performance optimization in the face of conflicting task demands. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Word frequency, repetition, and lexicality effects in word recognition tasks: Beyond measures of central tendency.

Response time (RT) distributions obtained from 3 word recognition experiments were analyzed by fitting an ex-Gaussian function to the empirical data to determine the main effects and interactive influences of word frequency, repetition, and lexicality on the nature of the underlying distributions. The ex-Gaussian analysis allows one to determine if a manipulation simply shifts the response time (RT) distribution, produces a skewing of the RT distribution, or both. In contrast to naming performance, the lexical decision results indicated that the main effects and interactions of word frequency, repetition, and lexicality primarily reflect increased skewing of the RT distributions, as opposed to simple shifts of the RT distributions. The implications of the results were interpreted within a hybrid 2-stage model of lexical decision performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dysregulation of cytokines during graft-versus-host disease

Modulation of stimulus luminance in a tachistoscopic face discrimination task has been found to significantly invert visual hemifield advantage in reaction time (RT) (Sergent, 1982a, Sergent, 1982b). However, there is no more physiological rationale for that than for a similar effect, say, of retinal adaptation, and it is even conceivable that the latter may have confounded the former in past experiments. The experiments reported here were therefore designed to tease out the relative contributions of stimulus luminance and of background illumination (i.e., retinal adaptation) in a simple RT task. Two equally difficult conditions of dim targets were set up, one with light-adapted subjects and one with dark-adapted subjects. Similarly, two equally difficult conditions of bright targets were set up with light and dark-adapted subjects. It was found that dim targets (near detection threshold) yielded a significant right visual field RT advantage in light-adapted subjects and that dim targets (equally near detection threshold) yielded a significant left visual field RT advantage in dark-adapted subjects. Future experiments will determine whether cone-mediated RT to detection is left hemisphere dominant and whether rod-mediated RT to detection is right hemisphere dominant.     

Adult age differences in the rate of learning serial patterns: Evidence from direct and indirect tests.

Ss performed a serial reaction time (RT) task (adopted from M. J. Nissen and P. Bullemer, 1987) that contained a repeating pattern of spatial locations. In Exp 1, following 20 repetitions of a 10- or 16-element pattern, RT was equally disrupted for both younger and older people when the sequence became random. In Exp 2, the response times for Ss encountering the 10-element pattern were compared with those of Ss encountering a random sequence. These response time functions diverged at the same point in training for the 2 age groups. Thus, on this indirect measure of response time facilitation, both experiments revealed age similarity in the rate of pattern learning. In contrast, on a subsequent direct test of pattern learning that required prediction, the younger people earned a higher percentage correct score than the older in both experiments. Age-related dissociations between direct and indirect measures of learning and comparisons with memory-impaired populations are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Signal recency effects can be distinguished from signal repetition effects in serial CRT tasks.

Reaction time (RT) is reduced in serial choice tasks when a particular signal, as distinct from the response made to it, is repeated on successive trials, N–1 and N. This experiment with 30 undergraduates showed a separate signal recency effect. RT is also reduced when a signal presented on trial N–2 recurs on trial N. In 3 many-to-one signal-to-response mapping tasks (2 responses 4 signals, 2 responses 8 signals, and 2 responses 16 signals), the effects of recent occurrence of signals were shown to be distinct from the effects of recent occurrence of responses made to them. The magnitude of signal recency effects varies directly with set size, but decreases, and may eventually disappear, with practice. The effect decreases with practice faster when signal sets are small than when they are large. A simple model accounts for these results and for earlier data from many-to-one mapping tasks that show that variations in signal entropy cease to affect choice reaction time if practice is sufficiently prolonged. Predictions from this model for changes in component RT distributions with signal set size, signal repetition, signal recency, and practice suggest further experiments. (French summary) (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The nature of word frequency effects on perceptual identification.

Four experiments, using a study–test paradigm, examined the effects of event presentation frequency on perceptual identification. In each cycle, subjects studied a list with different items presented from one to four or more times, then received identification tests of studied and nonstudied items. Pseudoword repetition (Experiments 1 and 4) produced a priming effect, that is, enhanced identification for presented items, and a repetition effect, that is, incremental improvements in identification for repeated items. In contrast, word repetition (Experiment 2, 3, and 4) produced priming but not repetition effects, a pattern that was not due to learning asymptotes or scaling distortions. We conclude that presentation frequency effects act on at least two distinct processing paths, selected on the basis of processing and task demands. Under conditions of simple exposure, perceptual enhancement is mediated, for codified events like words, primarily by nodal activation, and, for noncodified events like pseudowords, by information accumulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Response Conflict Determines Sequential Effects in Serial Response Time Tasks With Short Response-Stimulus Intervals.

In serial choice reaction time (RT) tasks, performance in each trial critically depends on the sequence of preceding events. In this study, the authors specifically examined the mechanism underlying RT sequence effects at short response-stimulus intervals (RSIs), in which performance is impaired in the current trial N if events alternate rather than repeat from trial N - 2 to trial N - 1. Different accounts of this RT pattern in terms of perceptual noise, response-selection monitoring, and response conflict were tested in 4 experiments. Second-order RT costs were caused by the response sequence rather than the stimulus sequence. Manipulation of stimulus contrast, stimulus classification difficulty, and set-level compatibility did not modulate the response-related second-order RT effect, whereas this effect increased when spatially incompatible responses were demanded. These findings support a response conflict account of higher order sequential effects in short-RSI situations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibition of return is not detected using illusory line motion

Inhibition of return (IOR) is the name that has been assigned to a response time (RT) delay to a stimulus presented at a recently stimulated spatial location. A commonly held explanation for the origins of IOR is that perceptual processing in inhibited and that this inhibition translates into slower RT. Three experiments with 10 subjects were used to directly test this perceptual explanation. The first two experiments assessed the level of perceptual facilitation present in the IOR paradigm using the frequency and latency of illusory line motion judgments. Contrary to the predictions of the perceptual view, the line motion and RT measures revealed only speeded processing at previously stimulated spatial locations. Experiment 3 required a simple detection response and used the same stimulus and timing parameters as those in Experiments 1 and 2. IOR was present, replicating the recent finding that judgments based on perceptual qualities of the stimulus do not demonstrate a RT delay, whereas simple detection tasks do show RT inhibition at previously stimulated locations. These findings are discussed in relation to a number of hypotheses about the origin of the RT delay.     

Discrimination of structure: II. Feature binding.

In 3 experiments, pigeons acquired a discrimination between patterns comprising the same features. Thus vertical green bars beside horizontal red bars might have signaled food, and horizontal green bars beside vertical red bars might have signaled no food. The solution of this discrimination can be explained by assuming each pattern is represented either by a template or by structural features that are sensitive to combinations of color and line orientation. The 1st explanation predicts subjects should react to a training pattern rotated 90° in the same way as the pattern on which it is based. The 2nd explanation predicts these patterns should be treated as if they signal opposing outcomes. The experiments confirmed the 2nd of these predictions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of irregular preparatory intervals on reaction time in schizophrenia.

2 experiments attempted to (a) confirm previous observations that the slope of the negative relationship between reaction time (RT) and the length of the preparatory interval (PI) was steeper in schizophrenic than in normal Ss, and (b) investigate the effects of the PI on one trial on RT to the subsequent trial (PPI). The results show that the curves relating the PI with RT are significantly steeper for the patients even when differences in "baseline" RT level are controlled. Also, the detrimental effects of long PPIs are much greater for the schizophrenics. The data suggest that instead of establishing a generalized preparatory set, the schizophrenic Ss simplify the task by basing their pattern of preparation largely on the just preceding trial. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sad and guilty? Affective influences on the explanation of conflict in close relationships.

What is the role of mood in the way people explain interpersonal conflicts in their close relationships? On the basis of the multiprocess Affect Infusion Model (AIM) of judgments (J. P. Forgas, 1992, in press), 3 experiments, with a total of 306 Ss, found a nonobvious pattern of greater mood effects on attributions for serious rather than simple conflicts. In Exp 1, sad Ss blamed themselves more for conflicts than did happy Ss. Exp 2 found that in a field setting, sad persons attributed real-life conflicts more to internal, stable, and global causes and did so more for serious than for simple conflicts. Exp 3 replicated these findings in the laboratory and also produced reaction time (RT) data showing that it was the longer processing recruited by more serious conflicts that accentuated these affect-priming effects, as predicted by the AIM. The cognitive mechanisms linking affect and judgments are discussed, and the role of moods in everyday explanations of conflict is considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Orientation congruency effects in visual search.

Studied 24 undergraduates who searched for the letter E in a background of letter Ls and Fs in displays that had 1, 2, 4, 8, or 12 letters. The letters could be shown at 1 of 6 orientations. The displays were either congruent for orientation or incongruent. Search time increased linearly with the number of letters in the display, and more so for E-absent trials than for E-present trials. Letter orientation, in general, increased search time and produced an M-shaped function. Results demonstrate systematic orientation effects on the time to search for a simple pattern embedded in simple backgrounds. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of Room Temperature and Cryo-Deformation Effects on Mechanical Properties and Microstructure of Copper

The objective of this work is to study the effect of room temperature (RT) and liquid nitrogen temperature (LNT) rolling on mechanical properties of the pure copper. For the same percentage deformation, LNT samples show a significant increase in tensile strength and hardness value compared to RT samples. Microstructural investigation shows a large misorientation change between RT and LNT samples when we use grain orientation spread (GOS) as a measure of microstructural change. The mechanical property and microstructural changes are correlated with calorimetry experiments. We also present some preliminary results from our work on wire drawing at RT and LNT.     

The time to identify disoriented letters: Effects of practice and font.

Measured the time taken by 32 undergraduates to name letters shown in 4 orientations (0–280°) and presented in a familiar or an unfamiliar font. Naming time increased linearly as the letters were rotated further from the upright from 0 to 120°, but not from 120 to 180°. The orientation effect on the time to identify letters was more pronounced for the less familiar font than for the more familiar font. The orientation effect was larger in the 1st half of the experiment than in the 2nd half, suggesting a practice effect. Results suggest that smaller orientation effects on letter identification time compared with the time to identify other types of visual patterns may be due to the visual familiarity of typical alphanumeric characters. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Transient structures": the effects of practice and distractor grouping on within-dimension conjunction searches

It has been stated that whereas between-dimension (color x orientation) conjunctions can be searched in a "parallel" fashion, within-dimension (color x color) conjunctions are necessarily searched in a "serial self-terminating" fashion (Wolfe et al., 1990). We explored the effects of practice (within 1-h experimental session) and distractor grouping on within-dimension conjunction search tasks. In Experiments 1 and 3, the stimuli were rectangles formed by two adjacent squares; in Experiment 2, the stimuli were plus signs formed by two segments and an intersection. In Experiments 1 and 2, observers were assigned to one of two experimental conditions: In one, all the distractors shared a simple feature (the color blue); in the other, distractors did not share that simple feature. In the first condition, search became more efficient with practice and observers' performance was characterized by a shallow reaction time (RT) x set size slope; in the second condition, observers' performance did not improve as much with practice. We propose that the differential effects of practice between these two experimental conditions can be explained in terms of distractor grouping induced by the shared color of the distractors. Experiment 3 showed that, with practice, a shallow RT x set size slope characterized observers' search for a color x color target among four different distractors that shared a common color. The present results contradict a main tenet of some current visual search models--namely, that within-dimension conjunctions cannot be searched in parallel, and question the validity of using RT x set size slope functions to distinguish between preattentive versus attentive search.     

Reading rotated words.

In 4 experiments, 72 Hebrew-speaking university students performed lexical decisions on Hebrew letter strings that appeared at different orientations. Response times evidenced a strong interaction between string length and orientation. At angular deviations of less than 60° from the upright, neither orientation nor string length had any effect, suggesting that words were directly, and probably holistically, recognized. The results for the 60° deviation, while also exhibiting no effects of word length, yielded slower response times, suggesting a holistic rectification process. For deviations between 60° and 120°, the effects of disorientation increased sharply with increasing string length, suggesting piecemeal processing than may be due to the utilization of reading units smaller than the whole word or to piecemeal rectification. In this region, stimulus disorientation appears to impair word recognition by disrupting transgraphemic information rather than by interfering with letter identification. Extreme disorientations, 120° or more, exhibited no further impairment with increased disorientation, and all evidenced strong and similar length effects, suggesting letter-by-letter reading. Implications for the reading of normal and transformed text are discussed. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of irrelevant stimulus orientation on visually guided grasping movements.

The present study investigated the effects of irrelevant stimulus orientation on visually guided grasping movements. Participants had to grasp a rectangular object at either the ends or the sides, depending on the color of a visual stimulus. In this task, correspondence between stimulus orientation and object orientation (stimulus-object congruency) and correspondence between stimulus orientation and hand orientation (stimulus-hand congruency) varied independently. Two experiments, with different sets of object orientations, revealed a consistent pattern of results. In particular, there were significant effects of stimulus-hand congruency, suggesting that perceiving an object activates congruently oriented hand movements. However, stimulus-object congruency had no effects, indicating that participants did not benefit from a preactivation of object orientation in the present task. The pattern of congruency effects implies that the cognitive representation, which is affected by irrelevant visual information, entails only those object or response features that are needed to select and control a response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Eye movements and the associative basis of contingent color aftereffects: A comment on Siegel, Allan, and Eissenberg (1992).

One of the recent S. Siegel et al (see record 1992-22207-001) arguments in support of associative-learning explanations of colored aftereffects (CAEs) is that the contingencies underlying these effects are not constrained by simple stimulus dimensions, such as contour orientation. Specifically, the authors claim to have generated CAEs contingent on sets of spatiotopic relationships between orientation components of a pattern (as opposed to orientation components per se). The present article illustrates how the Siegel et al claims are compromised by their failure to adequately address the role of fixation and eye movements during CAE induction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)