Influences of multiple spatial stimulus and response codes on orthogonal stimulus—response compatibility

When up-down stimuli are mapped to left-right responses, an up-right/down-left mapping advantage is found that is modified by response eccentricity and hand posture. These effects can be attributed to correspondence of asymmetric stimulus and response codes formed relative to multiple reference frames. We examined the influence of stimulus-set location on these orthogonal stimulus-response compatibility (SRC) effects. In Experiment 1, the stimulus set appeared in the upper or lower display positions. A spatial code for stimulus-set location was formed, producing Simon-type response eccentricity and hand posture effects, but this code had no influence on the coding of the relevant stimuli. In Experiment 2, the stimulus set appeared in the left, center, or right positions relative to the response location, which also varied, to dissociate the effects of response location, relative to the stimulus display and body midline. The former factor influenced the orthogonal SRC effect for both unimanual switch movements and bimanual keypresses, and the latter factor influenced the effect for only unimanual switch movements. Stimulus-set location causes orthogonal Simon-type effects when varied along the stimulus dimension and provides a referent for response coding when varied along the response dimension.     

Does stimulus appearance affect learning?

We examined the learning process with 3 sets of stimuli that have identical symbolic structure but differ in appearance (meaningless letter strings, arrangements of geometric shapes, and sequences of cities). One hypothesis is that the learning process aims to encode symbolic regularity in the same way, largely regardless of appearance. Another is that different types of stimuli bias the learning process to operate in different ways. Using the experimental paradigm of artificial grammar learning, we provided a preliminary test of these hypotheses. In Experiments 1 and 2 we measured performance in terms of grammaticality and found no difference across the 3 sets of stimuli. In Experiment 3 we analyzed performance in terms of both grammaticality and chunk strength. Again we found no differences in performance. Our tentative conclusion is that the learning process aims to encode symbolic regularity independent of stimulus appearance.     

Unlearning a stimulus–response association

After a response has been associated with a particular stimulus, would this association be “unlearned” when the circumstances call for a new response to be made to that stimulus? This question was investigated in the present study with a negative priming (NP) paradigm developed by Shiu and Kornblum (1996). In the study, participants first practiced with a particular pairing of stimuli and responses in a four-choice reaction time (RT) task. Then, in the transfer phase, they switched to a different pairing of the same set of stimuli and responses. The results showed that a transfer response was slow if this response and the stimulus in the preceding trial had been paired in the training phase. Such NP effects persisted even after extended practice with the new pairing, suggesting that the “old” stimulus–response (SR) associations remain despite acquisition of some “new” associations.     

Orthogonal stimulus–response compatibility effects emerge even when the stimulus position is task irrelevant

The above-right/below-left mapping advantage with vertical stimuli and horizontal responses is known as the orthogonal stimulus–response compatibility (SRC) effect. We investigated whether the orthogonal SRC effect emerges with irrelevant stimulus dimensions. In Experiment 1, participants responded with a right or left key press to the colour of the stimulus presented above or below the fixation. We observed an above-right/below-left advantage (orthogonal Simon effect). In Experiment 2, we manipulated the polarity in the response dimension by varying the horizontal location of the response set. The orthogonal Simon effect decreased and even reversed as the left response code became more positive. This result provides evidence for the automatic activation of the positive and negative response codes by the corresponding positive and negative stimulus codes. These findings extended the orthogonal SRC effect based on coding asymmetry to an irrelevant stimulus dimension.     

The influence of the response–stimulus interval on implicit and explicit learning of stimulus sequence

Three experiments investigated the influence of the response-stimulus interval (RSI) on implicit and explicit learning of stimulus sequences. Participants responded to numerals presented in predetermined positions with alternating long and short RSIs. Half of the participants were instructed explicitly to learn the position sequence. In the transfer phase of Experiments 1 and 2, changing RSI patterns reduced the expression of incidental and intentional learning of position sequence. In Experiment 3 the position sequence was transformed, except that sub-sequences demarcated by long RSIs remained unchanged; this greatly reduced the expression of intentional learning, and slightly reduced that of incidental learning. These results indicate that in implicit learning, stimulus sequences are learned under the constraints of RSIs, whereas in explicit learning, learning independent of RSIs, as well as learning constrained by RSIs, occurs.     

Effects of visual cue and response assignment on spatial stimulus coding in stimulus–response compatibility

Tlauka and McKenna (2000 Tlauka, M. and McKenna, F. P. 2000. Hierarchical knowledge influences stimulus–response compatibility effects. Quarterly Journal of Experimental Psychology, 53A: 85–103.  [Google Scholar]) reported a reversal of the traditional stimulus–response compatibility (SRC) effect (faster responding to a stimulus presented on the same side than to one on the opposite side) when the stimulus appearing on one side of a display is a member of a superordinate unit that is largely on the opposite side. We investigated the effects of a visual cue that explicitly shows a superordinate unit, and of assignment of multiple stimuli within each superordinate unit to one response, on the SRC effect based on superordinate unit position. Three experiments revealed that stimulus–response assignment is critical, while the visual cue plays a minor role, in eliciting the SRC effect based on the superordinate unit position. Findings suggest bidirectional interaction between perception and action and simultaneous spatial stimulus coding according to multiple frames of reference, with contribution of each coding to the SRC effect flexibly varying with task situations.     

Does intermodal equivalence exist between heteromodal stimulus dimensions or between stimulus values on those dimensions?

In a same--different judgement task with successively presented signals, subjects matched dots in different vertical positions and tones of different frequencies intramodally and intermodally. The first and second stimuli of trials in each of the four modality conditions were drawn from a set consisting of two, three or five alternatives. In all intermodal set size conditions, the dimensions of pitch and vertical position were related by the same equivalence rule. While intramodal performance improvement depended only on the total number of practice trials at matching on the relevant dimensions, intermodal performance improvement appeared to be related to the number of trials practice with each heteromodal stimulus pairing in a particular set. After performance had approached asymptotic level neither intramodal nor intermodal matching reaction time depended on set size. Mean “same” reaction time was less than mean “different” reaction time, and this difference was greater for intermodal matching than for intramodal matching. The results indicated that intermodal equivalence exists between discrete stimulus values on heteromodal dimensions rather than between the dimensons themselves.     

Is memory for stimulus magnitude Bayesian?

This study was designed to determine whether memory for stimulus values is a Bayesian weighting of the magnitude of a stimulus and the central tendency of an exemplar's category (Huttenlocher, Hedges, & Vevea, 2000). In five experiments, participants reproduced the remembered size of a geometric figure drawn from one of two categories whose means for size differed. Reproductions were biased toward the mean of the combined distribution rather than the mean of either category. Reproductions were also influenced by the size of the stimulus on the preceding trial. Neither of these results is entirely consistent with the view that recollections are partially constructed from a consideration of the long-run probabilities established by category membership.     

Why do categories affect stimulus judgment?

The authors tested a model of category effects on stimulus judgment. The model holds that the goal of stimulus judgment is to achieve high accuracy. For this reason, people place inexactly represented stimuli in the context of prior information, captured in categories, combining inexact fine-grain stimulus values with prior (category) information. This process can be likened to a Bayesian statistical procedure designed to maximize the average accuracy of estimation. If people follow the proposed procedure to maximize accuracy, their estimates should be affected by the distribution of instances in a category. In the present experiments, participants reproduced one-dimensional stimuli. Different prior distributions were presented. The experiments verified that people's stimulus estimates are affected by variations in a prior distribution in such a manner as to increase the accuracy of their stimulus reproductions.     

Is stimulus persistence affected by eye movements?

Summary When an eye movement intervenes between the presentation of a target and a mask, the mask has its effect on material projected on the same retinal position. Davidson, Fox, and Dick (1973) reported, however, that the mask appears to be positioned in real space, a suggestion which implies integration of visible information across the eye movement. The present note argues that their conclusion does not follow from their data.     

How prioritized is self-prioritization during stimulus processing?

Recent research has suggested that self-relevance automatically enhances stimulus processing (i.e., the self-prioritization effect). Notably, information associated with one’s self elicits faster responses than comparable material associated with other targets (e.g., friend, stranger). Challenging the assertion that self-prioritization is an obligatory process, here we hypothesized that self-relevance only facilitates performance when task sets draw attention to previously formed target-object associations. The results of two experiments were consistent with this viewpoint. Compared with arbitrary objects owned by a friend, those owned by the self were classified more rapidly when participants were required to report either the owner or identity of the items (i.e., semantic task set). In contrast, self-relevance failed to facilitate performance when participants judged the orientation of the stimuli (i.e., perceptual task set). These findings demonstrate the conditional automaticity of self-prioritization during stimulus processing.     

Two pathways to stimulus encoding in category learning?

Category learning theorists tacitly assume that stimuli are encoded by a single pathway. Motivated by theories of object recognition, we evaluated a dual-pathway account of stimulus encoding. The part-based pathway establishes mappings between sensory input and symbols that encode discrete stimulus features, whereas the image-based pathway applies holistic templates to sensory input. Our experiments used rule-plus-exception structures, in which one exception item in each category violates a salient regularity and must be distinguished from other items. In Experiment 1, we found discrete representations to be crucial for recognition of exceptions following brief training. Experiments 2 and 3 involved multisession training regimens designed to encourage either part- or image-based encoding. We found that both pathways are able to support exception encoding, but have unique characteristics. We speculate that one advantage of the part-based pathway is the ability to generalize across domains, whereas the image-based pathway provides faster and more effortless recognition.     

Can response preparation begin before stimulus recognition finishes?

The present experiments were designed to determine whether information obtained early in the process of recognizing a stimulus can be used to begin preparing keypress responses before recognition of the stimulus has completely finished. This question is relevant to the recent debate between discrete (e.g., Sternberg, 1969a) and continuous (e.g., McClelland, 1979) models of human information processing. Stimulus sets were chosen so that recognition processes could extract incomplete preliminary information about a stimulus much faster than they could extract secondary information needed for unique stimulus identification. Discriminability of the secondary information was manipulated to vary the opportunity for response preparation based on preliminary information, with difficult secondary discriminations providing more time for response preparation than easy ones. Precues were given on some trials to allow response preparation to occur before the stimulus was presented, thereby reducing any difference in response preparation as a function of discriminability. Continuous models predict that precues should facilitate response preparation less when the secondary discrimination is difficult than when it is easy, and discrete models predict equal facilitation regardless of secondary discrimination difficulty. Evidence of response preparation was obtained with some but not all stimulus sets. The results were interpreted as support for the asynchronous discrete coding model (Miller, 1982a), in which response preparation can begin only after recognition processes have completely activated a code used in categorizing the stimulus.     

Does previewing one stimulus feature help conjunction search?

We examined the effects of previewing one aspect of a search display, in order to determine what subset of display information is most useful as a prelude to a search task. Observers were asked to indicate the presence or absence of a known target, in a conjunction search where the target was defined by the combination of colour and orientation (a yellow horizontal line presented among yellow vertical and pink horizontal distractors). In the colour preview condition of experiment 1, observers were first shown a 1 s preview of the locations and colours of the search items before the actual search set was presented. That is, search items first appeared as yellow and pink squares for 1 s, which each then turned into yellow and pink oriented lines (in the same locations) which comprised the display to be searched. In the orientation preview condition, observers were first shown a 1 s preview of the locations and orientations of the search items before the actual search display was presented. These two conditions were compared to a control condition consisting of standard conjunction search without any preview display. There was no effect of colour preview; there was a marginal effect of orientation preview, but in the opposite direction from what was expected reaction time increased for orientation preview searches. In experiment 2 these previews were compared to two spatial cueing conditions; in this experiment the colour preview did provide a small amount of help. Finally, in experiment 3 both previews were presented in succession, and increased facilitation was found, in particular when the colour preview preceded the orientation preview. These findings are discussed in relation to the literature, in particular the Guided Search model (Wolfe et al 1989 Journal of Experimental Psychology: Human Perception and Performance 15 419-433; Wolfe 1994 Psychonomic Bulletin & Review 1 202-238).     

Does stimulus context affect loudness or only loudness judgments?

Marks (1988) reported that when equal-loudness matches were inferred from magnitude estimates of loudness for tones of two different frequencies, the matches were affected by changes in the stimulus intensity range at both frequencies. Marks interpreted these results as reflecting the operation of response biases in the subjects' estimates; that is, the effect of range was to alter subjects' judgments but not necessarily the perception of loudness itself. We investigated this effect by having subjects choose which of two tone pairs defined the larger loudness interval. By using tones of two frequencies, and varying their respective intensity ranges, we reproduced Marks' result in a procedure devoid of numerical responses. When the tones at one frequency are all soft, but the tones at the other frequency are not all soft, cross-frequency loudness matches are different from those obtained with other intensity range combinations. This suggests that stimulus range affects the perception of loudness in addition to whatever effects it may have on numerical judgments of loudness.     

Implicit sequence learning is represented by stimulus—response rules

For nearly two decades, researchers have investigated spatial sequence learning in an attempt to identify what specifically is learned during sequential tasks (e.g., stimulus order, response order, etc.). Despite extensive research, controversy remains concerning the information-processing locus of this learning effect. There are three main theories concerning the nature of spatial sequence learning, corresponding to the perceptual, motor, or response selection (i.e., central mechanisms underlying the association between stimulus and response pairs) processes required for successful task performance. The present data investigate this controversy and support the theory that stimulus—response (S—R) rules are critical for sequence learning. The results from two experiments demonstrate that sequence learning is disrupted only when the S—R rules for the task are altered. When the S—R rules remain constant or involve only a minor transformation, significant sequence learning occurs. These data implicate spatial response selection as a likely mechanism mediating spatial sequential learning.     

Responding to a positive stimulus by “satiated” pigeons

Skinner (1938) found that rats given discrimination training (Phase I) and then reinforced to “satiation” for responses in the presence of the negative stimulus (S?) (Phase II), began to respond again when the positive stimulus (S+) was reintroduced (Phase III). Experiment I replicated Skinner's finding with pigeons, alternating S+ and S? presentations during Phase III. In Experiment II, Phase II was extended, and Phase III results were similar to those of Experiment I, demonstrating that the recovery of S+ responding could not be attributed to a lax Phase II satiation criterion. In Experiment III, a uniform schedule of reinforcement was maintained throughout the three phases, and results similar to those of Experiment I were found, indicating that renewed S+ responding was not due to the shift in schedule between phases. In Experiment IV, Phase I consisted of discrimination training with two positive stimuli (S+_s and S+_n), and Phase II consisted of reinforcement for responses in the presence of S? and S+_s. During Phase III, significantly more responding was found to S+_s and S+_n than to S?, but no difference in responding was found between the two positive stimuli. In Experiment V, Phase I consisted of simple discrimination training, and during Phase II, responses in the presence of both S? and a novel stimulus (So) were reinforced. During Phase III, significantly more responding was found to S+ than to either S? or So, with no difference found between S? and So responding. Renewed responding to S+ during Phase III in the present experiments is best explained by behavioral contrast developed during Phase I.     

Does backward masking by visual noise stop stimulus processing?

The identification of one, two, and four random letters was studied under three procedures: (1) backward masking by a visual noise; (2) concurrent masking by a visual noise; and (3) no masking. With backward masking the number of letters correctly identified was independent of the number presented. Direct judgments of the duration, brightness, contrast, sharpness, and texture of the letters were also made. Under backward masking the letters appeared to be on for a very brief duration, but with high apparent contrast. The results indicate that backward masking impairs identification by interrupting the stimulus processing, not by degrading the stimulus input.     

Effects of face and inanimate-object contexts on stimulus–response compatibility

Prior studies have shown that a left–right spatial compatibility effect occurs for vertically oriented stimuli relative to a background context of a face rotated 90° clockwise or counterclockwise from upright. For stimuli presented at the location of the eyes, the mapping of the right eye to a right response and the left eye to a left response, as would be viewed by the participant, yields better performance than does the opposite mapping. An issue of current interest in social cognition is whether animate objects are processed differently from inanimate ones. We investigated this issue in two experiments in which we compared the compatibility effects obtained with inanimate objects to those obtained with animate, face stimuli. The results showed left–right compatibility effects from the participant’s perspective for vehicles and faces from frontal and profile views, as well as for a road sign. Our findings indicate that coding of stimulus location relative to an external frame of reference is not restricted to face backgrounds.     

Influence of stimulus–response assignment on the joint-action correspondence effect

Sebanz et al. (Cognition 88:B11–B21, 2003) have shown that spatial correspondence effects are observed even when the two-choice reaction time task is distributed between two people, such that each person is assigned only one of two possible stimulus–response (S–R) pairings. The effect is similar to when one person is assigned and responds to both S–R pairings. These results have been taken to suggest that two people performing a complementary task co-represent each other’s response alternatives. In our experiment, we examined performance when paired participants responded to the same S–R alternative. We reasoned that co-representation would be of little advantage as the task alternatives would be the same for both participants. Correspondence effects were absent when paired participants responded to the same S–R alternative but emerged when they responded to different alternatives.