Parallel visual processing: Constant same-different decision latency with two to fourteen shapes

Fourteen Os were shown 2, 5, 8, 11, or 14 geometric shapes at a 200-msec exposure. The maximum visual extent was the same for all numbers of shapes. The stimulus conditions were: all shapes identical, 1 shape different from the rest, and, for 5 to 14 shapes, 3 shapes different (4 shapes in all). The number of shapes, the condition, and the shapes used varied randomly through the sequence of 160 exposures. Decision latency to correct same or different response was independent of the number of shapes presented. Correct same and three-different decisions were faster than one-different decisions, but with two shapes different decisions were faster than same. The results suggest that same-different decisions are made with information processed in parallel from many stimuli     

Individual differences in visual comparison processes

Two experiments are reported in which subjects compared the shape of two successively presented random visual forms. The first stimulus in the pair was one of five “standard” shapes, and the second stimulus was either the same as the standard or different by virtue of a perturbation in shape or an overall reflection. Marked individual differences were found in reaction time for the same-different comparison. For one type of subject “same” responses were faster than “different” responses, speed of “different” responses was unaffected by similarity of the test shape to the standard, and error rates and reaction times were not systematically related. For the other type of subject, “different” responses were generally faster than “same” responses, “different” reaction time decreased as the standard shape and the test shape became increasingly dissimilar, and error rates and reaction times were positively correlated. Implications of these individual differences for models of the same-different comparison process are discussed.     

Reaction times for a same-different discrimination of vowel-consonant syllables

Reaction times (RTs) were measured for decisions in a same-different discrimination of successive vowel-consonant nonsense syllables. Averaged data showed that “same” RTs were faster than “different” RTs and that the “different” RT decreased as the number of features (Wickelgren, 1966) by which a pair contrasted increased. For individual phonemic comparisons, two of the dependent variables, P(S I d), or probability of responding “same” to a different trial and the mean correct “different” RT, were related in that the RT increased as P(S I d) increased. The size of the difference between “same” and “different” RTs for a given phonemic contrast was directly related to P(S | d). The difficulty of a comparison, as described by P(S I d) and by the difference between correct “same” and “different” RTs, was explained through a markedness classification of phonemes.     

Multidimensional same--different judgments: evidence against independent comparisons of dimensions

Commonly discussed models of performance in the multidimensional same-different task are based on the assumption that independent same-different decisions are reached for each of the stimulus dimensions used in an experiment. In these models, a higher level mechanism examines th outcome of these independent decisions in order to determine whether the stimuli are the same or different overall. Previous evidence indicating that these models are inconsistent with results from same trials is summarized, and a new test of the above assumption using data from different trials is proposed. Detailed analysis of reaction times from different trials is shown, at least for some pairs of dimensions, to be incompatible with the view that separate same-different decisions are reached for each dimension. The major finding is that there are more relatively fast responses in a condition with two dimensions different, compared with the two conditions with only one of the dimensions different, than any processing model treating the dimensions separately could predict. The results suggest that partial information may be combined across dimensions in order to reach a "different" judgment.     

Effects of array organization on same-different judgments

Two experiments investigated the role of array organization in the simultaneous matching task. Multielement arrays of letters were arranged in either “good” or “poor” configurations and subjects were asked to determine whether all the letters were the same or if at least one was different. Correct “different” responses were slower when the letters were presented in good configurations than in poor configurations. Correct “same” responses, however, were not affected by the organizational quality (goodness) of the array. This effect of pattern goodness on matching performance was not affected by the confusability of the letters being compared, the relative eccentricity (spread) of the configuration, or the ratio of different letters present on different trials. The results suggest an encoding stage locus for the effect of pattern goodness and provide evidence supporting a two-process model of same-different judgments.     

Transformation processes upon the visual code

Seven experiments investigated whether orientation-dependent latency functions for the visual code resemble those observed in studies of mental rotations of visual images. The subjects were required to perform “same-different” classifications of two simultaneously presented letters. The dependent variables considered were reaction time IRT and accuracy. Experiments 1, 2, 4, 5, and 6 showed that subjects could correctly classify two different letters on the basis of the visual code without preceding transformations. Experiments 1, 2, and 7 showed orientationdependent effects for “same“ responses. It appeared, however, that orientation functions for the visual cede were clearly different from those previously observed for visual images. In addition, the findings of Experiments 4, 5, and 6 indicated that a frame that jointly rotated with the disoriented letters could eliminate the orientation-dependent effects for “same” responses. Experiment 7 showed that the results of Experiments 4, 5, and 6 must be attributed to the structural characteristics of the frame and not to a directional cue. The results of Experiment 3 seemed to demonstrate that transformations did not occur when the subjects used the phonetic code to classify the letters. Overall, the results of the seven experiments were considered to provide a demonstration of the importance of the distinction between the operations on visual images and those on the visual code.     

Association learning and visual discrimination

The effect of learned stimulus associations on visual discrimination was measured in four experiments. The stimuli were visual shapes which had been scaled for similarity. Two shapes were selected as discriminanda, and each S was pretested and posttested for discrimination of these briefly presented simultaneous pairs of “same” and “different” shapes. During the training, each discriminandum was paired with another simultaneously presented associated shape on a paired-associate response-learning task. The two associated shapes were very similar, intermediate in similarity, or very dissimilar. There was more improvement in posttest discrimination following training with dissimilar associates. We conclude that learned stimulus associations affect visual discrimination.     

Reaction times and error rates for “same”-“different” judgments of multidimensional stimull

Each S indicated whether two successively presented rows of letters were “same” or “different.” Reaction times of the “different” response seemed to indicate that S examined the stimulus letters in a serial, self-terminating manner. However, the reaction times of the “same” response were not consistent with this model. Consequently, it was proposed that S employs simultaneously two distinct processes for comparing stimuli. One process would generate the “different” responses; the other process would generate the “same” responses. Most false “same” responses occurred when the two rows of letters differed minimally. Thus, the false “same” responses appear to result from a failure to detect the difference between the two stimuli. However, when S made a false “same” response, he was aware that he had done so. Therefore, it was suggested that only one of the two comparison processes failed to detect the stimulus difference.     

Response probabilities and “same-different” reaction times

A “same-different” reaction-time (RT) task with multidimensional stimuli was used with a 50:50 and a 75:25 proportion of “different” to “same” response. The “different” RTs to each dimension were similar for the two proportions. However, the “same” RT in the 50:50 condition was faster than the “same” for the 75:25 condition and faster than the slowest “different” RT. Interpretations of the results in terms of response bias and processing criteria are offered.     

Additivity and interaction between size ratio and response category in the comparison of size-discrepant shapes

In Experiment 1, subjects made same-different judgments to pairs of shapes that could differ (irrelevantly) in size and in which different pairs combined distinct shapes. Size discrepancy had an effect both on same and different responses. However, the effect on different responses was not monotonic across size discrepancies. It is argued that this nonmonotonicity was produced by a form of bias acting to slow different responses for same-sized pairs. Consistent with the proposed bias account, the nonmonotonic size-discrepancy effect on different trials was eliminated in Experiment 2, in which trials were blocked by size ratio. In Experiment 3, subjects performed a task similar to that in Experiments 1 and 2. However, additional visual information was added inside the bounding contour of the shapes, and this information was either the same or different across shapes. The match between within-contour information across shapes (whether same or different) was varied orthogonally with whether the bounding contours of the shapes were the same or different. In this experiment subjects decided whether the bounding contours of the shapes were the same or different, while ignoring the added information within the contours. When the added information matched across the two shapes, same responses were facilitated relative to when the added information mismatched. The converse occurred for different responses. This effect was more pronounced when the shapes were shown at the same size than when the shapes were at different sizes. In general, the results suggest that (a) size discrepancy affects some perceptual operations that are preliminary to shape matching, and (b) bias mechanisms can play an important role in shape-matching experiments in which the shapes can be shown in different sizes. The interaction of two processes--size scaling and bias--can account for these and hitherto contradictory results in the literature.     

Reaction times in a task analogous to “same”-“different” judgment

Subjects responded “yes” if two equal-length strings of letters contained a common letter in a common position; otherwise they responded “no.” Thus, the task was to judge whether all or not all of the letters in one string differed from the letter occupying the corresponding position in the other string. Conversely, in “same”-“different” judgment, the task is to judge whether all or not all of the letters in one string match the corresponding letter in the other string. Thus, common-letter judgment and “same”-“different” judgment are symmetrically related with “no” analogous to “same” and “yes” analogous to “different.” The response “same” is often faster than the response “different.” However, in the common-letter task, “no” was slower than “yes.” More specifically, both the “yes” and “no” reaction times were consistent with a serial self-terminating search. This is precisely what would be expected from Bamber’s (1969) two-process model.     

The effect of explicitly varying the proportion of “same” and “different” responses on sex differences in the Shepard and Metzler mental rotation task

The mental rotation of three-dimensional objects is consistently identified as the most salient cognitive sex difference in humans. The Shepard and Metzler task (1971) requires participants to rotate an object in their “mind's eye” and then compare the shape to a second object to identify if the two objects can be aligned in an identical orientation (warranting a “same” response) or represent mirror image shapes of one another (warranting a “different” response). The mental rotation task not only involves a rotational component but also nonrotational components such as comparison and decision making. Recent research has suggested that the sex difference in mental rotation resides in the nonrotational aspects of “different” decisions specifically. This experiment examined this proposal by varying the proportion of “different” decisions across conditions. Participants were ether exposed to the traditional format (50:50 same/different) or a bias towards (75:25) or away from (25:75) different responses. Contrary to previous research, the sex difference was found to reside in “same” responses that required a greater degree of rotation when assessing error rates in mental rotation. Sex differences in mental rotation error rates were particularly sensitive to the rotational aspect of same responses, not rotational aspects of different responses nor nonrotational aspects of both same and different responses. For reaction time, however, a sex difference emerged in the nonrotational aspects of the task. The bias described here affected these nonrotational aspects of the task, but not the rotational aspects, in line with prediction. A second study reran the experiment without making the bias explicit. Under this implicit bias, no sex differences were identified between conditions.     

Comprehension of "absence" by an African Grey parrot: Learning with respect to questions of same/different

An African Grey parrot, Alex, learned to report on the absence or presence of similarity and difference between two objects. Alex was shown pairs of objects that were (a) totally dissimilar, (b) identical, or (c) similar or different with respect to one of three attributes (color, shape, or material). In the first two cases, he responded to the respective queries of “What's same?” or “What's different?” with the vocalization “none,” and in the third case he responded with the appropriate category label (“color,” “shape,” or “mah-mah” [matter]). His accuracy was 80.9% to 83.9% for pairs of familiar objects not used in training and 72.5% to 78.4% for pairs whose colors, shapes, and materials were unfamiliar. The data provide evidence that this parrot's abilities are comparable to those of mammals that have been trained to report on the presence or absence of objects or features of objects.     

异同判断中“快同效应”的大脑机制：一项ERP研究

采用高密度的事件相关电位（ERPs）技术,记录分析了大学生被试在执行异同判断任务[包括不同颜色刺激对（DC）,不同形状刺激对（DS）和相同刺激对（Same）]时的脑内时程动态变化。行为结果表明,“同”反应的确显著快于“异”反应,表现出明显的快同效应。ERP结果显示：在280-320 ms内,DS和DC条件均比Same条件诱发一个更负的N2成分。偶极子溯源分析表明,DC和DS条件下,N2可能起源于大脑的前扣带皮层（ACC）,可能与“异”反应早期不一致信息（颜色或形状）的认知监控和调节有关;反之Same条件下,N2成分可能起源于楔前叶,主要反映了“同”反应早期知觉识别中整体特征比较加工的过程（同一性指示器）。另外,在450 ms左右, DC和DS比Same条件均诱发了一个更负的P3成分,可能反映了对刺激局部特征的比较和识别（慢速比较器）,并与选择性注意和资源分配等高级认知活动有关;并且,Same条件下P3成分的潜伏期更短,与行为结果一致。以上研究结果表明,异同判断中“同”反应和“异”反应可能有着不同的比较通道和大脑机制,支持双过程模型理论;同时表明,慢速比较器和同一性指示器可能是序列加工的。     

Common features of the “repetition” and “same-different” effects in reaction time experiments

Using comparable stimulus and response sets, and the same Ss, the “repetition” and “same-different” effects were studied in two experiments involving several reaction-time (RT) tasks. In Experiment 1, these effects were examined at a 2-sec interval between successive stimuli in the simple (SRT), the recognition (RRT), the choice (CRT), the same-different recognition(S-DRRT),and the same-different choice (S-DCRT) tasks. In Experiment 2, the effects were studied at a 1 O-sec interval in the CRT and S-DCRT tasks. The results suggest the following mainconclusions: (1)The positive repetition effect (i.e., shorter reaction times on “repeated” trials than on “nonrepeated” trials) is not only a feature of the CRT task but may also occur in the SRT and RRT tasks. (2) With increasing intertrial interval, the magnitude of the positive repetition effect diminishes and then reverses into a negative repetition effect. (3) The positive same-different effect (ie., shorter reaction times on “same” trials than on “different” trials) is affected by an increase in interstimulus interval ina manner that parallels the effect of intertrial interval on the positive repetition effect, suggesting that the processes underlying the two effects are mainly the same. (4) These changes in the magnitude and direction of the repetition and same-different effects are probably a function of discrimination difficulty.     

The effect of irrelevant surround on speeded visual discriminations varying in complexity

To measure the effect of varying stimulus material on visual matching, a three-factor experimental design was employed, with “same”-“different” RT as the main dependent variable. Pairs of sequences of meaningless shapes served as stimuli, varying in discriminability (high or low), complexity (sequence lengths of 1, 2, 5, or 8 shapes), and level of pair difference (identical sequences or sequences with one pair differing). All independent variables significantly affected RT, with (a) high-discriminability stimuli being reacted to faster than low, (b)RT increasing with sequence pair length, and (c)“same”-response RTs interacting with “different”-response RTs. A significant triple-order interaction component implied that, while a single-process self-terminating feature testing model could accommodate data from the low-discriminability condition, the high-discriminability data did not fit this model. The results are taken as support for a dual-process model to account for the data from “same”-“different” RT tasks. epaxtment of     

Further confirmation ofsame vs.different processing differences

Two four-digit numbers were matched in a “same-different” reaction time paradigm. In the “all-same” condition, the subject respondedsame if all digits matched anddifferent otherwise. In the “all-different” condition, the subject responded same if at least one digit matched anddifferent if all digits differed. In either condition, the number of matching digits ranged from zero to four. The all-same results supported previous work: the fewer the number of mismatches, the slower the response, except that zero mismatches resulted in a response faster than one mismatch. These findings have been taken as supporting a two-process model: an identity detector mechanism and a self-terminating feature-matching process. An alternative one-process model could explain the results by assuming that the “same” response is primed during the match process. However, the all-different results showed reaction time to be a monotonie function of the number of matching digits. Such a finding contradicted the priming model and supported a two-process model.     

Cerebral Asymmetry and Decision Strategies in Mental Rotation: A Psychophysical Analysis

The accuracy with which observers judged the parity of pairs of rotated images in the two visual fields was determined from receiver operating characteristic (ROC) analysis of confidence ratings. In one experiment, observers judged whether pairs of letters were of the same parity (that is, both normal or both backwards) or of different parities (one normal and one backwards). A small right visual field advantage in the observers' accuracy was found in this mental rotation task. In a second experiment, observers judged whether pairs of pictures were of the same parity or of different parities. Unlike the first experiment, no evidence of a consistent visual field advantage was found in this mental rotation task. The decision strategy adopted by the observers in making same-different judgements about rotated stimuli was examined. The symmetrical shape of the ROCs obtained was consistent with the adoption of the likelihood-ratio decision strategy, a result which supplemented previous evidence that this decision strategy is adopted when same-different judgements are made about multidimensional stimuli.     

You better stop! Binding “stop” tags to irrelevant stimulus features

We investigated whether the basic process of integrating stimuli (and their features) with simultaneously executed responses transfers to situations in which one does not respond to a stimulus. In three experiments, a stop-signal task was combined with a sequential priming paradigm to test whether irrelevant stimulus features become associated with a “stop” tag. Stopping a simple response during the prime trial delayed responding and facilitated stopping in the probe if the same irrelevant stimulus feature was repeated in the probe. These repetition priming effects were independent of the relation between the to-be-executed (or to-be-stopped) responses in the prime and probe, indicating that “stop” tags are global (“stop all responses!”) rather than being response-related (e.g., “stop left response!”).     

Does implicit speech in same-different decisions extend to nonsense forms?

A previous study (Klapp, 1971) demonstrated that response latencies for same-different decisions involving printed words and numbers depend on the number of syllables needed for pronunciation. In the present experiment, Ss first learned to associate one- or two-syllable words to nonsense form stimuli. After extensive overlearning, the Ss were transferred to a same-different decision task involving these nonsense forms. Latencies were independent of number of syllables in the learned response. This was interpreted as showing that the Ss did not use the responses to mediate their same-different decisions, in contrast to the apparent implicit pronunciation for decisions involving printed words and numbers.