Attentional processes in time perception: effects of mental workload and event structure

The role of attention in timing was evaluated in 2 experiments. In Experiment 1, participants reproduced the durations of melodies with either a coherent or an incoherent structure. Participants were tested under control (timing only) and detection (timing plus target detection) workload conditions. Reproductions were shorter and more inaccurate under detection conditions, and incoherent event structure extended the effect to a wider range of durations. In Experiment 2, participants reproduced the durations of auditory prose passages that represented 3 levels of mental workload and 3 levels of event structure. Both increases in workload and the degradation of structure led to inaccurate reproductions. The results point to the central role of attention in temporal experience.     

Probability effects in choice reaction time tasks

This paper contains a short review of the main results that were obtained by the author in a series of experiments that constituted a study of the effects of signal probability on choice reaction time. The effects of stimulus probability are shown to be influenced by the following variables: (1) differences in the method of varying stimulus probability, (2) differences in task complexity, (3) differences in S-R code, and (4) differences in Ss’ motivation. The data that are considered here are the overall mean RT for particular signals and the mean RT for sequential repetitions. Two questions, related to the psychological “nature” of the probability effects in choice RT are discussed: (1) The question of the relationship between the relative frequency and the number of alternatives as two different ways of determining the probability effect in choice RT; and (2) the question of identifying the main determinants of the trial-to-trial variability of RT in such experiments.

     

Wavelength effects on simple reaction time

Simple reaction time was measured to spectral lights matched photometrically in luminance. When these lights were presented on a dimmer achromatic background, reaction time did not vary as a function of wavelength. Moreover, reaction times to white and chromatic lights were the same. When the luminance of the background was the same as that of the chromatic lights, reaction time increased and showed a strong effect of wavelength. Reaction time in this condition appeared to follow a saturation function. The results are described in terms of the operation of achromatic and chromatic processing channels.     

Modeling spatial effects in visual-tactile saccadic reaction time

Saccadic reaction time (SRT) to visual targets tends to be shorter when nonvisual stimuli are presented in close temporal or spatial proximity, even when subjects are instructed to ignore the accessory input. Here, we investigate visual-tactile interaction effects on SRT under varying spatial configurations. SRT to bimodal stimuli was reduced by up to 30 msec, in comparison with responses to unimodal visual targets. In contrast to previous findings, the amount of multisensory facilitation did not decrease with increases in the physical distance between the target and the nontarget but depended on (1) whether the target and the nontarget were presented in the same hemifield (ipsilateral) or in different hemifields (contralateral), (2) the eccentricity of the stimuli, and (3) the frequency of the vibrotactile nontarget. The time-window-of-integration (TWIN) model for SRT (Colonius & Diederich, 2004) is shown to yield an explicit characterization of the observed multisensory spatial interaction effects through the removal of the peripheral-processing effects of stimulus location and tactile frequency.     

Modeling spatial effects in visualtactile saccadic reaction time

Saccadic reaction time (SRT) to visual targets tends to be shorter when nonvisual stimuli are presented in close temporal or spatial proximity, even when subjects are instructed to ignore the accessory input. Here, we investigate visualtactile interaction effects on SRT under varying spatial configurations. SRT to bimodal stimuli was reduced by up to 30 msec, in comparison with responses to unimodal visual targets. In contrast to previous findings, the amount of multisensory facilitation did not decrease with increases in the physical distance between the target and the nontarget but depended on (1) whether the target and the nontarget were presented in the same hemifield (ipsilateral) or in different hemifields (contralateral), (2) the eccentricity of the stimuli, and (3) the frequency of the vibrotactile nontarget. The time-window-of-integration (TWIN) model for SRT (Colonius & Diederich, 2004) is shown to yield an explicit characterization of the observed multisensory spatial interaction effects through the removal of the peripheral-processing effects of stimulus location and tactile frequency.     

Sequential effects in auditory choice reaction time tasks

This paper concerns sequential effects in choice reaction time tasks. Performance in two interleaved auditory tasks was examined, and two general types of sequential effects were revealed. First, a response repetition effect occurred: Subjects were facilitated in responding when both the stimulus and the response were immediately repeated. Generally, it appeared that subjects were operating according to the bypass rule—that is, repeat the response if the stimulus or some aspect thereof is repeated from the preceding trial; otherwise, change the response. In addition, the experiment also revealed a second type of sequential effect, known as a task-switching effect. Subjects were overall slower to respond when the task changed between adjacent trials than when there was no task change. A final result was that subjects were markedly impaired when the stimulus changed but the same response had to be repeated. This finding has been reported elsewhere when purely visual tasks have been used. Hence, it seems that particular difficulties arise, in such sequential testing situations, when type-distinct stimuli are grouped into the same response categories.     

Experience-dependent effects in unimanual and bimanual reaction time tasks in musicians

Engaging in musical training has been shown to result in long-term cognitive benefits. The authors examined whether basic cognitive-motor processes differ in people with extensive musical training and in nonmusicians. Musicians (n = 20) and nonmusicians (n = 20) performed a simple reaction time (RT) task under unimanual and bimanual conditions. Musicians' RTs were faster overall than were those of nonmusicians, and those who began their musical training at an earlier age (around age 7-8 years, on average) exhibited a larger bimanual cost than did those who began later (around 12 years, on average). The authors conclude that experience-dependent changes associated with musical training can result in greater efficacy of interhemispheric connections if those changes occur during certain critical periods of brain development.     

Online psychophysics: reaction time effects in cognitive experiments

Using the Internet to acquire behavioral data is currently on the rise. However, very basic questions regarding the feasibility of online psychophysics are still open. Here, we aimed to replicate five well-known paradigms in experimental psychology (Stroop, Flanker, visual search, masked priming, attentional blink) in three settings (classical “lab”, “web-in-lab”, “web”) to account for possible changes in technology and environment. Lab and web-in-lab data were both acquired in an in-lab setting with lab using “Gold Standard” methods, while web-in-lab used web technology. This allowed for a direct comparison of potential differences in acquisition software. To account for additional environmental differences, the web technology experiments were published online to participate from home (setting web), thereby keeping the software and experimental design identical and only changing the environmental setting. Our main results are: First, we found an expected fixed additive timing offset when using web technology (M = 37 ms, SD = 8.14) and recording online (M = 87 ms, SD = 16.04) in comparison to lab data. Second, all task-specific effects were reproduced except for the priming paradigm, which couldn’t be replicated in any setting. Third, there were no differences in error rates, which are independent of the timing offset. This finding further supports the assumption of data equality over all settings. Fourth, we found that browser type might be influencing absolute reaction times. Together, these results contribute to the slowly but steadily growing literature that online psychophysics is a suitable complement – or even substitute – to lab data acquisition.     

Identification and pronunciation effects in a verbal reaction time task for words,pseudowords, and letters

The question addressed in this investigation was whether faster reading and pronunciation of words than orthographically regular pseudowords is due to faster identification or to faster programming and execution of the motor response. In Experiment I, three different response conditions (naming, threechoice signaled responding, and one-choice signaled responding) were employed to separate the identification and articulation processes in a verbal reaction time task. It was found that, for all intents and purposes, single, isolated letters are processed as if they were very short words. Words are read and pronounced 72 msec faster than pseudowords. Words are also pronounced 30 msec faster than pseudowords even if the reader has longer than 1 sec to identify the stimulus (three-choice condition) or to both identify the stimulus and preprogram the response (one-choice condition). The data indicate that words are identified about 52 msec faster and articulated about 30 msec faster than pseudowords. Since the number of response alternatives (one or three) does not interact with stimulus type (letter, word, or pseudoword) in the signaled response control condition, the 30-msec difference is due to response execution and not to differential response programming. Response programming takes in the neighborhood of 236 msec. Experiment 2 investigated the effect of local orthographic context upon the identification of the first letter of a string of letters. No difference was found in identifying the initial letter of words and pseudowords, but the initial letter of these orthographically regular letter strings was identified and named 10 msec faster than the initial letter of orthographically anomalous strings of letters (anagrams). The data from the two experiments are supportive of theories of reading that assume (1) that the letters of visually presented words are processed simultaneously, in parallel, (2) that there is a relatively direct access and retrieval of the phonological memory codes for the names of words, and (3) that orthographically regular pseudowords having no representation in the phonological lexicon undergo a grapheme-to-phoneme transformation that takes longer to finish than the direct spelling-to-sound process used for words.     

Repetition effects in choice reaction time to multidimensional stimuli

Ss classified as quickly as possible stimuli back-projected one at a time on a small screen by pressing one of two levers in response to each stimulus, according to the levels of a single specified binary stimulus dimension. Stimuli were rectangles varying in height alone, in width alone, or in both dimensions, in either a correlated or an orthogonal fashion. Stimuli followed responses by a fixed interval of 82, 580, or 1,080 msec. Response time was longer when both dimensions varied orthogonally than when only one dimension varied, indicating that Ss were unable to avoid perceiving the rectangle figures as wholes. Repeated stimuli were responded to more quickly than stimuli which were different from the immediately preceding stimulus in all conditions. With orthogonally combined dimensions, response time to stimulus repetitions was lowest, increased when the stimulus changed while the response was repeated, and increased still further when both the stimulus and the response changed. Increasing the time interval between stimuli decreased response time for nonrepetitions, while response time for repetitions was relatively unaffected. The results were discussed in terms of two models of serial choice reaction time.     

Specific sequence effects in the serial reaction time task

The Serial Reaction Time (SRT) task was used in 2 experiments to determine if the specific sequence used by the task influences implicit learning. In Experiment 1, participants performed the SRT task with the locations of the stimuli determined by a commonly used fixed sequence (taken from P. J. Reber & L. R. Squire, 1998), by a fixed sequence that was uniquely generated for each participant, or at random. Experiment 2 used the same basic design, but the random condition was changed so that each possible transition between responses was seen the same number of times, making it more comparable to the fixed-sequence conditions. Results from both experiments indicate that the specific sequence used in the SRT task influences the strength of implicit learning effects. Follow-up analyses show that the strength of implicit learning can be linked to the presence of particular types of triads within the sequence. The authors suggest that future researchers should not use on a single fixed sequence across all participants when using the SRT task but should instead generate different fixed sequences for each participant to enhance the generalizability of their results.     

On quantifying multisensory interaction effects in reaction time and detection rate

Both mean reaction time (RT) and detection rate (DR) are important measures for assessing the amount of multisensory interaction occurring in crossmodal experiments, but they are often applied separately. Here we demonstrate that measuring multisensory performance using either RT or DR alone misses out on important information. We suggest an integration of RT and DR into a single measure of multisensory performance: the first index (MRE*) is based on an arithmetic combination of RT and DR, the second (MPE) is constructed from parameters derived from fitting a sequential sampling model to RT and DR data simultaneously. Our approach is illustrated by data from two audio–visual experiments. In the first, a redundant targets detection experiment using stimuli of different intensity, both measures yield similar pattern of results supporting the “principle of inverse effectiveness”. The second experiment, introducing stimulus onset asynchrony and differing instructions (focused attention vs. redundant targets task) further supports the usefulness of both indices. Statistical properties of both measures are investigated via bootstrapping procedures.     

Sequential effects of catch-trials on choice reaction time

The aim of the study was to examine whether or not choice reaction time (RT) depends on catch-trial frequency. The results show a significant increase of mean RT as the catch-trial frequency increases from zero to 0.77. A similar effect has been shown previously in simple RT experiments. The interpretation of these effects on simple RT supposes the existence of an inverse relationship between catch-trial frequency and anticipated response frequency. This cannot be extended to a choice RT task since the subject must wait for the stimulus to arrive before deciding which is the appropriate response. The interpretation of the present results proposes preparatory adjustments prior to the arrival of the stimulus. Sequential effects found suggest that (1) the tendency to prepare for a stimulus at a trial was stronger when a stimulus was presented at the preceding trial than after a catch-trial, and (2) the frequency effects of catch-trials can be explained completely in terms of sequential effects.     

Sequential effects in an eight choice serial reaction time task

Data from an eight choice serial reaction time experiment using two different response-stimulus intervals were examined for sequential effects by separating out the mean reaction times for each stimulus following every other stimulus. This analysis revealed differences in performance under the two response-stimulus interval conditions not shown by the conventional partitioning of the reaction times into those for repetitions and for non-repetitions.     

Variable criterion analysis of brightness effects in simple reaction time

Using light onset as the stimulus in simple reaction time (SRT), the effect of stimulus intensity was studied in both between-subjects and within-subjects experimental designs. There was a strong intensity effect in both conditions but no significant interaction between the effect of stimulus intensity and the type of design. This differs from previous results with auditory stimuli where such an interaction has been demonstrated. When the criterion parameters of variable criterion theory were evaluated directly, the only significant effect was greater criterion variability in the between-subjects condition. Theoretical functions describing the growth of sensory strength for each intensity had different starting points and were largely parallel, showing only late temporal divergence. This provides an explanation of the rarity, in the SRT literature, of interactions between visual intensity and criterion variables. Correlations illustrating the relations between reaction time (RT) measures and theoretical criterion parameters are presented. Absence of the predicted relation between intensity and RT variability is evidence against theories relating RT to impulse rate treated as a Poisson process.