Roberto Nicoletti

Spatial Stimulus-Response Compatibility

Publisher Summary This chapter describes the different aspects of the spatial stimulus-response (S-R) compatibility. A stimulus dimension is relevant when the required response depends on the value of the stimulus in that dimension, whereas a stimulus dimension is irrelevant if values on it are uncorrelated with the required response. It is found that by combining dimensional overlap with dimensional relevancy, four types of S-R ensembles are obtained. The type-I ensemble occurs when there is no dimensional overlap in either the relevant or the irrelevant dimension. Ensemble type II is characterized by the presence of dimensional overlap in the relevant dimension. It satisfies the condition for obtaining S-R compatibility effects. Most of the studies with Type II ensembles use spatial stimulus and response dimensions. A light is presented in the left or in the right visual field and the subject is required to press either the left or the right key in response. Response time is faster when the imperative stimulus and the response are on the same side than when they are on opposite sides. It is found that in all studies that showed S-R compatibility effects with Type III ensembles, the irrelevant dimension was spatial. The correspondence in space is a particularly powerful way of obtaining an overlap between stimulus set and response set.

Why are left-right spatial codes easier to form than above-below ones?

Previous studies have shown that spatial compatibility is stronger in the left-right than in the above-below dimension. This left-right dominance cannot be attributed to a better representation of the effectors in left-right than in above-below locational codes or to the fact that incompatible left-right stimulus-response pairings cross the body midline, whereas incompatible above-below ones do not. Nicoletti and Umiltà (1985) proposed that the left-right dominance should be attributed to the allocation of attention to the more difficult discrimination, which, in vision, is that concerning the left-right dimension. This attentional hypothesis was tested in the present study, in which we used the auditory modality. We reasoned that because in the auditory modality the above-below discriminations are more difficult than left-right ones, attention should be preferentially allocated to the former. Therefore, in audition an above-below dominance should replace the left-right dominance observed in vision. Experiments 1 and 2 showed a clear-cut compatibility effect in the auditory modality for both the left-right and above-below dimensions. Experiment 3 showed that spatial compatibility was still stronger for the left-right than for the above-below dimension. Since the left-right one proved to be the more discriminable dimension, this finding rules out the attentional hypothesis, at least in the version originally proposed.

The cost of a strategy

Abstract Experiment 1 demonstrated a new kind of dual-task interference effect. The primary task was a speeded left-right discrimination of stimulus position (R1). The un speeded secondary task consisted of reporting verbally whether the stimuli were the same or different (R2). Stimulus exposure time was either 150 or 2000 msec. Two groups of subjects performed the primary task only, whereas two other groups performed both tasks and were instructed to emit R1 before R2. It was reasoned that the decision would be made to emit R1 before R2, and that this decision would produce a lengthening of R1. The results supported this prediction. Experiment 2 showed that the interference effect also occurred when the subjects were not explicitly instructed to emit R1 before R2, and was not due to either the mere presence of the second task or to response grouping. Experiments 3 and 4 compared two possible models for explaining the interference effect, i.e. the capacity-sharing model and the postponement model. As pred...

Response strategies and the Simon effect

Abstractu2002The study investigated whether the Simon effect, and its facilitation and interference components, shows up in reaction time (RT) or in movement time (MT), depending on the response strategy. Experiment 1 replicated a study by Hietanen and Rämä. Subjects had to press one of two lateralised keys in response to one of two stimuli. The stimuli were presented in the center (neutral condition) or to the left or right side (corresponding or non-corresponding conditions). To press the response key, a reaching movement was necessary, and both RT and MT were recorded. One group of subjects showed an RT facilitation effect and an MT interference effect. Another group of subjects showed both MT facilitation and MT interference effects. It was hypothesized that the two groups used different response strategies. In Exps. 2 and 3, the subjects were explicitly instructed to use the two strategies that were hypothesized for Exp. 1. The results showed that whether facilitation and interference manifest themselves in RT or MT depends on the response strategy adopted by the subjects.

Right—left prevalence effect with horizontal and vertical effectors

We investigated the right-left prevalence effect in spatial compatibility tasks by assessing subjects’ performance on a two-dimensional task in which both the horizontal and vertical spatial dimensions were task relevant. Two experiments were performed, in which stimulus-response mappings were one-dimensional (Experiment 1) and two-dimensional (Experiment 2). The subjects responded by using either horizontal or vertical effectors to stimuli appearing in four possible locations. With the one-dimensional mapping, the spatial compatibility effect was present only in the dimension relevant to the mapping. With the two-dimensional mapping, the horizontal compatibility effect was always present, whereas the vertical compatibility effect was present only when vertical effectors were used. This pattern of results indicates that horizontal coding takes place with either horizontal or vertical effectors, whereas vertical coding takes place only when vertical effectors are used.

New evidence for the perceptual precedence of global information

Two experiments are reported investigating the order in which global and local information of visual forms is processed. Subjects were presented with compound stimuli and were asked to identify the local level, always consisting of small letters. At the global level, the stimuli could be either large letters, consistent or inconsistent with the local level, or meaningless patterns derived from the large letters by modifying the spatial relations among segments. Results showed that inconsistent stimuli were responded to more slowly than both consistent stimuli and meaningless patterns, which did not differ from each other. This was true both when letters and patterns were presented intermixed, as in experiment 1 or separately, as in experiment 2. The pattern obtained accords well with predictions derived from the perceptual precedence hypothesis which states that global information becomes available at a faster rate than local information. No support for the alternative, post-perceptual, hypothesis was found.

Shifting attention between objects

Experiment 1 used a modified spatial cueing paradigm that was introduced by Egly et al. [J. Exp. Psychol. Gen. 123 (1994) 161] to investigate the cost incurred in shifting attention within an object as opposed to shifting attention between objects. Subjects were presented with two outline rectangles and had to detect a target (a luminance increment) that could appear in the cued location (valid trials), in an uncued location inside the cued rectangle (inside-invalid trials), or in an uncued location inside the uncued rectangle (outside-invalid trials). Valid trials were faster than invalid trials, and inside-invalid trials were faster than outside-invalid trials. In Experiment 2, the two rectangles were joined to form a unitary object. Here, no difference was found between outside-invalid trials and inside-invalid trials. Experiment 3 showed that the delayed response on outside-invalid trials in Experiment 1 was not due to attention needing to cross the figural borders in order to re-orient to the uncued rectangle. The results were interpreted as showing that an extra cost is incurred for shifting attention between different objects.

Age-related slowing of control processes: evidence from a response coordination task.

Normal aging is associated with slowing of performance mostly due to a slowed functioning of central response-related processes. In this paper we set out to discover whether slowing occurs also when the process controlling the coordination of responses is engaged by the task. To this end, we compared the mean-reaction time performance of two groups of subjects (young vs. elderly) in single- and dual-task experimental paradigm. The response coordination process is required only by the dual-task paradigm. The results indicate that, in the dual-task situation, the elderly are markedly slower than young subjects. The eventual relevance of information-processing speed in determining the cognitive performance of the elderly is considered in the discussion of the results.

Modulation of the vertical Simon effect in two-dimensional tasks: The effect of learning

The present work was aimed at investigating whether automatic two-dimensional spatial coding, as indexed by the Simon task, is affected by prior practice with a vertical spatial compatibility task. One group of subjects performed a two-dimensional Simon task in which the vertical Simon effect was absent. The other group practised the vertical dimension by performing a vertical spatial compatibility task before the two-dimensional Simon task. With prior practice, the vertical Simon effect was significant. These results are discussed in the framework of the factors that affect two-dimensional spatial coding.

Processing of global and local information in memory

The experiments reported in this paper were designed to test how global and local information are processed by the memory system. When subjects are required to match a given letter with either a previously presented large capital letter or the small capital letters comprising it, (1) responses to the global level (i.e. the big letter) are faster than responses to the local level (i.e. the small letters), and (2) responses to the latter level only are affected by the consistency between the large and the small letters (Experiment 2), a pattern similar to that obtained in perception (Experiment 1). Such results obtain when subjects are required to attend to only one level with a short ISI between the first and second stimulus, but not when a longer ISI is used (Experiment 5) or when subjects are required to attend to both levels at the same time (Experiments 3 and 4). The results are discussed in the light of a model that postulates a temporal precedence of the global information over the local one at the perceptual level.