Perceptual processing and speed-accuracy trade-off.

Three experiments are described on speed-accuracy trade-off during a visual fixation. In a typical trial subjects started by fixating a fixed position at their left side at which a degraded digit (SL) was presented. At about the same time an intact digit (SR) was briefly presented at a fixed right side position. SL and SR were separated by a binocular visual angle of 45 degrees. The task was to verbally report both digits, which implied that the eyes should be rapidly shifted from SL to SR, so as not to miss SR. Under these conditions the distribution of the fixation latencies of SL appeared to consist of two parts, suggesting the occurrence of either anticipations or reactions. This argues against a strategy of optional stopping of information accrual during the fixation of SL and is in line with a strategy of either fully neglecting or fully encoding SL. However, this interpretation meets the difficulty that, at trials where SL is reacted to, subjects showed a shorter fixation latency than in a control condition, in which they had ample time to view both SL and SR. The results of the second and third study supported the view that, when under time stress, subjects can end a fixation as soon as a preliminary code of SL is obtained. This code (a) is insensitive to the complexity of SL, (b) cannot be elaborated during the saccade to SR, and (c) can be used as a starting point for further analysis, as soon as the eyes reach SR.     

Processing irrelevant location information: Practice and transfer effects in choice-reaction tasks

Left or right keypresses to a relevant stimulus dimension are faster when the stimulus location, although irrelevant, corresponds with that of the response than when it does not. This phenomenon, called the Simon effect, persisted across 1,800 trials of practice, although its magnitude was reduced. Practice with the relevant stimulus dimension presented at a centered location had little influence on the magnitude of the Simon effect when irrelevant location was varied subsequently, and practice with location irrelevant prior to performing with location relevant slowed responses. After practice responding to stimulus location with an incompatible spatial mapping, the Simon effect was reversed (i.e., responses were slower when stimulus location corresponded with response location) when location was made irrelevant. When the response keys were labeled according to the relevant stimulus dimension (the Hedge and Marsh [1975] task variation), this reversal from practice with a spatially incompatible mapping was found for both the congruent and the incongruent relevant stimulus-response mappings. Thus, task-defined associations between stimulus location and response location affect performance when location is changed from relevant to irrelevant, apparently through producing automatic activation of the previously associated response.     

Selective attention in the speeded classification and comparison of multidimensional stimuli

Selective attention was studied when subjects were required to make either speeded classifications of single stimuli or comparisons of pairs of multidimensional stimuli. Experiment 1 established that subjects were able to attend selectively to form when the irrelevant dimension of size or shading varied in a speeded-classification (card-sorting) task. Experiment 2 confirmed this finding in a discrete-trials task. However, subjects werenot able to filter out irrelevant dimensional disparity in a comparably designed simultaneous-comparison (i.e., “same”-“different”) task. Mean “same” reaction time increased monotonically with increases in disparity between the two stimuli on the irrelevant dimension. Experiment 3 also revealed a monotonie increase in “same” RT as a function of irrelevant disparity in a successive-comparison task. These results were discussed in terms of a normalization model proposed by Dixon and Just (1978) in which it is assumed that a subject equates the two stimuli on the irrelevant dimension before deciding that they are the same along the relevant dimension. It was concluded that: (1) although subjects can efficiently filter out irrelevant disparity in a speeded-classification task, interference due to irrelevant disparity is obtained in the comparison tasks, (2) a common process such as normalization does not necessarily underlie performance in the speeded-classification and comparison tasks, (3) the ability to attend selectively to a stimulus dimension may be task determined as well as stimulus determined, and (4) contrary to the Dixon and Just proposal, normalization of irrelevant disparity occurs in a comparison task, even when the relevant dimension is represented as a separate encoding feature.     

Parafoveal processing of transposed-letter words and nonwords: evidence against parafoveal lexical activation

The current experiments explored the parafoveal processing of transposed-letter (TL) neighbors by using an eye-movement-contingent boundary change paradigm. In Experiment 1 readers received a parafoveal preview of a target word (e.g., calm) that was either (1) identical to the target word (calm), (2) a TL-neighbor (clam), or (3) a substituted-letter (SL) nonword (chem). In Experiment 2 a further set of parafoveal preview conditions was explored including (4) an SL-word condition (chum) and (5) a TL-nonword condition (caml). Across both experiments, readers' fixation durations on the target words were significantly longer when the previews were SL previews than when they were TL neighbors, suggesting that TL neighbors (when presented in the parafovea) facilitate processing rather than inhibit processing. Experiments 3 and 4 showed that this is in contrast to the inhibitory effects that are seen when TL neighbor previews appear in the fovea.     

The Eriksen flanker effect revisited.

Four studies are reported on the potential role of perceptual interference in a standard Eriksen flanker task. In the first study, incongruent flanker letters showed the usual effect on choice reaction time (CRT) to the target letter but had no effect on the visual fixation time (VFT) needed to distinguish target and flankers. In the second experiment, the effect of incongruent flankers was studied in the context of a same-different response in regard to the target letter and a subsequently presented single letter. The effect of incongruent flankers vanished at an interstimulus interval of 200 ms. In Experiment 3, the same-different task was used in the paradigm of the functional visual field with a target-flankers combination as stimulus on the left (SL) and a single letter as stimulus on the right side (SR) of the visual field. Flankers did neither affect VFT nor the same-different CRT suggesting that target selection may proceed during the saccade from SL to SR. In Experiment 4 effects were studied of flanker-to-target and target-to-single-letter similarity. Flanker-to-target similarity did neither affect VFT nor same-different CRT but target-to-single-letter similarity prolonged same-different CRT. Together, the results suggest parallel perceptual processing of target and flankers, followed by competition of responses to the target and to the incongruent flankers. In line with earlier research, processes of response selection and response competition appear not to be tied to VFT but to proceed in parallel with the saccade from SL to SR.     

Cognitive operations associated with individual differences in affect intensity

There are wide individual differences in the characteristic intensity of affective response to the same emotion-evoking event. The processes whereby individuals come to experience strong or mild emotional responses when exposed to the same affect-provoking stimuli are still unclear. In these studies, we propose that individual differences in affect intensity are associated with certain cognitive operations used during exposure to emotion-relevant stimuli. Specifically, cognitive operations that involve personalizing, generalizing, and selective abstraction were hypothesized to discriminate subjects high and low in affect intensity. Two studies replicated support for the hypothesis that subjects high on the affect-intensity dimension engage in more personalizing/empathic and more generalizing/elaborative cognitive operations than do subjects low on the affect-intensity dimension. The same cognitive operations discriminated groups high and low in affect intensity in response to both positive and negative emotional stimuli. Also, the cognitions that discriminated subjects high and low in affect intensity occurred only in response to affective stimuli; neutral stimuli did not evoke divergent cognitive operations for these two groups. Finally, a high degree of consistency was found in the use of emotion-relevant cognitive operations across positive and negative affective stimuli.     

Display-control arrangement correspondence and logical recoding in the Hedge and Marsh reversal of the Simon effect

When left and right keypresses are made to stimuli in left and right locations, and stimulus location is irrelevant to the task, responses are typically faster when stimulus location corresponds with response location than when it does not (the Simon effect). This effect reverses when the relevant stimulus-response mapping is incompatible, with responses being slower when stimulus and response locations correspond (the Hedge and Marsh reversal). Simon et al. (Acta Psychol. 47 (1981) 63) reported an exception to the Hedge and Marsh reversal for a situation in which the relevant stimulus dimension was the color of a centered visual stimulus and the irrelevant location information was left or right tone location. In contrast, similar experiments have found a reversal of the Simon effect for tone location when relevant visual locations were mapped incompatibly to responses. We conducted four experiments to investigate this discrepancy. Both results were replicated. With an incompatible mapping, irrelevant tone location showed a small reverse Simon effect when the relevant visual dimension was physical location but not when the color of a centered stimulus or the direction in which an arrow pointed conveyed the visual location information. The reversal occurred in a more standard Hedge and Marsh task in which the irrelevant dimension was location of the colored stimulus, but only when the response keys were visibly labeled. Several of the results suggest that display-control arrangement correspondence is the primary cause of the Hedge and Marsh reversal, with logical recoding playing only a secondary role.     

Attention,instruction, and response representation

A two-dimensional Simon-type task was devised to investigate the impact of task requirements and explicit instructions on spatial action coding. Subjects performed actions that were defined on two spatial dimensions: horizontal (left-right) or vertical (top-bottom). The relevant stimulus feature was nonspatial but the stimuli varied on the horizontal and the vertical dimension, so that horizontal and vertical S-R compatibility effects could be measured separately. Implicit task requirements were manipulated by having the subjects perform an unrelated task before the Simon task—a task in which only one of the two spatial dimensions was relevant. Instructions were varied by describing the responses in the unrelated priming task and/or in the Simon task in spatial terms or by referring to nonspatial features of the response keys. Priming a particular dimension increased the Simon effect on that dimension, whereas instructions had no differential effect. These findings suggest that, first, drawing attention to a particular dimension leads to a stronger contribution to event representation of those features defined on that dimension (intentional weighting) and, second, that instructions do not affect action coding if the manipulation does not change the task goal.     

Encoding processes in memory scanning tasks

Three experiments are presented that deal with the effect of stimulus probability on the encoding of both alphanumeric characters and nonsense figures. Experiment I replicated a previous finding of an interaction between stimulus probability and stimulus quality in a memory scanning task with numbers as stimuli. Experiments II and III investigated the same paradigm with unfamiliar visual forms as stimuli, and no interaction was found. Results were interpreted as showing that probability affects the encoding mechanism only when the encoding process results in a representation of the name of the stimulus. When stimulus materials are visual forms without names, probability does not appear to affect encoding processes.     

Limitations of object-based feature encoding in visual short-term memory

The present study investigated object-based feature encoding in visual short-term memory for 2 features within the same dimension that occur on different parts of an object. Using the change-detection paradigm, this experiment studied objects with 2 colors and objects with 2 orientations. Participants found it easier to monitor 1 rather than both features of such objects, even when decision noise was properly controlled for. However, no object-based benefit was observed for encoding the 2 features of each object that were of the same dimension. When similar stimuli were used but the 2 features of each object were from different dimensions (color and orientation), an object-based benefit was observed. These results thus impose a major constraint on object-based feature encoding theories by showing that only features from different dimensions can benefit from object-based encoding.     

Programming response duration in a precueing reaction time paradigm

To determine whether the duration of certain motor activities can be a prespecified dimension of the motor program, we studied the duration of a motor response and the hand to be used, in a precueing paradigm. The response to be produced (a press on a push-button) was either short or long and involved either the right or the left hand. In Experiment 1, 200 and 700 ms (Block 1) or 700 and 2,500 ms (Block 2) were respectively chosen as short and long durations. No RT difference between short and long appeared when response duration was certain. When response duration was uncertain, RTs were longer for long than for short responses. In addition, the RTs that preceded the 700-ms response were longer in Block 1 than in Block 2. These results suggest that response duration can be programmed up to 2,500 ms and that the relative duration of a response in a given range is more relevant for programming mechanisms than its absolute duration. In Experiment 2, uncertainty concerning the response was maintained constant in a similar precueing paradigm, in which only 700-and 2,500-ms response durations were considered. The RTs preceding a long duration were shorter when duration was certain than when neither side nor duration was certain. No RT difference appeared before the short response duration. This seems to confirm that duration can be programmed up to 2,500 ms and also suggests that the program elaborated for the short duration constitutes a common basis for short and long responses: When duration is uncertain, programming a long duration requires just an additional operation to complete the program corresponding to the short duration, which has already been selected by default.     

Blocking of incidental information in young children

Methods of increasing learning efficiency through a blocking technique were examined in young children. An experimental group of children was trained on an initial task with one relevant dimension, followed by redundancy training in which an incidental dimension also became relevant. A control group given only redundancy training was compared to this group to test how much the experimental subjects blocked or screened out the incidental dimension. In order to increase blocking, three methods were used: a preset transfer problem, an overtraining on the initial task, and a delay following training. The most important finding was increased blocking through the Preset Condition. Overtraining and Delay Conditions had no effect. In addition, more slow learners on the initial task learned about the incidental dimension than fast or intermediate learners. Also, fewer subjects given form on the initial task learned about the incidental dimension than those given color. The Combined Blocking, Delay, and Overtraining group showed partial blocking, while the Preset group demonstrated complete blocking. No developmental differences occurred. The results were interpreted using a modification of Trabasso and Bower's attention model (Attention in learning: Theory and research. New York: Wiley, 1968).     

Conceptual memory for picture and prose episodes

In two experiments, subjects decided whether probes were true or false of one of some previously studied picture and prose episodes. The results indicated that response times to probes depicting explicit events were faster when they were in the same modality (picture or prose) as their episodes than when they were in the opposite modality, but response times to probes depicting implicit events were as fast when they were in the opposite modality as when they were in the same modality. These results suggest that the conceptual representations of picture and prose episodes are identical in form. The second experiment indicated that probes could be evaluated as fast from long as from short episodes. This result is consistent with the notion that retrieving information from episodes is done, not by scanning all the events of an episode, but by restricting the search only to the relevant slot in the schema into which the episode is assimilated.     

Coincidence anticipation of young normal and handicapped children

Two coincident-timing experiments examined the role of three different target velocities and display extents and three age levels of normal and retarded children. Subjects made a ballistic response to a target moving horizontally across their visual field. In the first experiment there were generally no clear differences between normal and retarded children on the task, with subjects having difficulty for both the slow and fast target speeds. In the second experiment, with target velocity held constant, no significant differences were reported between normal and handicapped children, although the longer the subjects were allowed to view the target the more accurate they were. The data were discussed in terms of the response strategies to perform anticipatory ballistic movements. An ecological issue was raised which suggested that children as well as adults make their most accurate anticipations when confronted with velocity problems that have been experienced in their everyday world.     

Reaction times to auditory and visual stimulation in schizophrenic and normal subjects

An experiment carried out to determine the relation between auditory and visual reaction times suggested that when the general level of response is slow visual RTs are faster than auditory, and that the reverse is the case when the level of response is fast. Thus most normal subjects have an auditory RT faster than visual, and most schizophrenics the reverse. However, the difference between auditory and visual RTs does not appear to depend directly on schizophrenic pathology except in so far as this is a factor in the general slowness of reaction time.     

Rate of processing and judgment of response speed: comparing the effects of alcohol and practice

Both alcohol and practice affect choice reaction time. The present study was conducted to investigate the possibility that impairment from alcohol and improvement with practice could be attributed to changes in the efficiency of control mechanisms (Rabbitt, 1979a), some of which depend upon the ability to judge response speed accurately. Twenty subjects participated in a four-choice reaction time experiment in which they received no alcohol (NA) in Session 1 and either no alcohol (10 subjects) or 0.8 ml alcohol (A) per kilogram of body weight (10 subjects) in Session 2. The task was to respond as fast and as accurately as possible to each stimulus. In addition, subjects were required to press a fifth key after any response that they considered to be both fast and accurate. Subjects had no difficulty in performing this task: (1) there was a significant difference of 122 msec between the mean response time for correct responses indicated as fast and that for correct responses not indicated as fast, and (2) subjects indicated 1 in 4 correct responses but only 1 in 64 errors. Alcohol increased all response times by approximately 40 msec. In contrast, practice decreased response times less for correct responses not indicated as fast than for correct responses indicated as fast. The ability to distinguish between fast and slow responses was thus unaffected by alcohol, but was improved by practice. Responses indicated as "fast" were significantly faster than errors, and appeared to occur without warning (unlike errors, which tended to end a sequence of increasingly fast correct responses). The results suggest that alcohol and practice influence choice reaction time in qualitatively different ways: Alcohol impairs overall response speed but has no effect on the ability to judge response speed, whereas practice improves both.     

Isolating the effects of symbolic distance,and semantic congruity in comparative judgments: An additive-factors analysis

The time needed to compare two symbols increases as the cognitive distance between them on the relevant dimension increases (symbolic distance effect). Furthermore, when subjects are told to choose either the larger or the smaller of two stimuli, the response time is shorter if the instruction is congruent with the overall size of the stimuli (semantic congruity effect). Three experiments were conducted to determine the locus of these effects in terms of a sequence of processing stages. The developmental aspects of these effects were also evaluated, as the subjects were from kindergarten, first grade, third grade, fifth grade, and college. By varying the visual quality of the stimulus in each experiment, it was determined that the distance effect resides in a comparison stage, whereas the congruity effect is an encoding phenomenon. Both distance and congruity effects were present at all grade levels, but they decreased in magnitude as grade increased. The results were interpreted relative to recent models of comparative judgments.     

Adaptation to prisms: Do proprioceptive changes mediate adapted behaviour with ballistic arm movements?

In Experiment I subjects pointed repeatedly at a target viewed through laterally displacing prisms and received terminal visual feedback. In one task the pointing movements were slow (proprioceptively controlled), and in the other they were fast (pre-programmed). In both tasks adaptation proceeded at the same rate and to the same level of performance. Following fast pointing with prisms a large amount of arm-body adaptation was found with slow and fast test movements, while following slow pointing with prisms a large amount of arm-body adaptation was found with slow test movements, but only a small amount with fast test movements. The result suggests that adapted behaviour with preprogrammed movements is not mediated by a proprioceptive change. In Experiment II pointing movements were passive. No arm-body adaptation was found with fast test movements, and, contrary to expectation, only a small amount with slow test movements.     

Tests of encoding tradeoffs between item and associative information

The assumption that item and associative information are processed separately and that there is a tradeoff in the amount of each type of information that can be encoded in a given study interval (e.g., Anderson & Bower, 1972; Murdock, 1982, 1992) was examined. When item information was emphasized at study, recognition memory for associative information was poor, demonstrating that item information can be emphasized over associative information. In contrast, when associative information was emphasized, associative recognition greatly improved but item recognition did not suffer. This pattern of results was found at both fast and slow presentation rates, and for both high and low word concreteness and word frequency. Measures of confidence and response latency were also consistent with this pattern. Thus, the encoding of associative information did not measurably diminish item recognition performance.     

Control of a continuous response dimension by a continuous stimulus dimension

Pigeons were trained to respond to stimuli from a continuous stimulus dimension (tonal frequency) with response values from a continuous response dimension. Both the number of points of correspondence and problem difficulty were varied. After training, subjects were tested with stimulus values intermediate to those trained. During these test tones, subjects emitted only those response values reinforced during training. The study suggested that if there are fast and efficient methods to obtain control of a continuous response dimension by a continuous stimulus dimension, these methods must depend on factors other than simple generalization.