Frequency correlates in grapheme-color synaesthesia

Individuals with synaesthesia experience certain stimuli in more than one sensory modality. Most common is the linkage of letters and digits (graphemes) to colors. Whereas synaesthesia might be partly genetically determined, the linkages to specific colors are assumed to be learned. We present a systematic statistical analysis of synaesthetic color perception based on subjects' reproduction of individual colors for each grapheme, instead of simple verbal categorizations. The statistical analysis revealed that the color perceptions, measured with the HSL (hue, saturation, and luminance) scale, varied systematically among the different digits and letters. The frequencies of the digits and letters (in the German language) partly explained these systematic variations. However, digit frequency was more strongly related to color perception in the synaesthetes than was letter frequency. The results for digit and letter frequency indicate that experience with graphemes may shape synaesthetic color perception.     

Ovals of time: time-space associations in synaesthesia

We examine a condition in which units of time, such as months of the year, are associated with specific locations in space. For individuals with this time-space synaesthesia, contiguous time units such as months are spatially linked forming idiosyncratically shaped patterns such as ovals, oblongs or circles. For some individuals, each time unit appears in a highly specific colour. For instance, one of the synaesthetes we studied experienced December as a red area located at arms length to the left of their body. For the same individual May was a blue area located roughly at arms length to the right of their body. We studied four synaesthetes who report spatial associations for the months of the year. We found that the time-space associations experienced by these individuals were consistent across test-retest. In addition, month names directed visual attention to particular locations in space. For some synaesthetes, this directing of spatial attention was quite rapid-in accord with their reports that month names involuntarily bring to mind spatial locations.     

Levels of selective attention revealed through analyses of response time distributions

The present research examines the nature of the interference effects in a number of selective attention tasks. All of these tasks result in interference in performance by presenting information that is irrelevant to task performance but competes for selection. The interference from this competing information slows the response time (RT) of participants relative to a condition where the competition is minimized. The authors use a convolution of an exponential and a Gaussian (ex-Gaussian) distribution to examine the influence of interference on the characteristics of RT distributions. Consistent with previous research, the authors show that interference in the Stroop task is reflected by both the Gaussian and exponential portions of the ex-Gaussian. In contrast, in 4 experiments they show that several other interference tasks evidence interference that is reflected only in the Gaussian portion of the ex-Gaussian distribution. The authors suggest that these differences reflect the operation of different selection mechanisms, and they examine how sequential sampling models accommodate these effects.     

How to fit a response time distribution

Among the most valuable tools in behavioral science is statistically fitting mathematical models of cognition to data—response time distributions, in particular. However, techniques for fitting distributions vary widely, and little is known about the efficacy of different techniques. In this article, we assess several fitting techniques by simulating six widely cited models of response time and using the fitting procedures to recover model parameters. The techniques include the maximization of likelihood and least squares fits of the theoretical distributions to different empirical estimates of the simulated distributions. A running example is used to illustrate the different estimation and fitting procedures. The simulation studies reveal that empirical density estimates are biased even for very large sample sizes. Some fitting techniques yield more accurate and less variable parameter estimates than do others. Methods that involve least squares fits to density estimates generally yield very poor parameter estimates.     

Multifractal analyses of response time series: A comparative study

Response time series with a non-Gaussian distribution and long-range dependent dynamics have been reported for several cognitive tasks. Conventional monofractal analyses numerically define a long-range dependency as a single scaling exponent, but they assume that the response times are Gaussian distributed. Ihlen and Vereijken (Journal of Experimental Psychology: General, 139, 436–463, 2010) suggested multifractal extensions of the conventional monofractal analyses that are more suitable when the response time has a non-Gaussian distribution. Multifractal analyses estimate a multifractal spectrum of scaling exponents that contain the single exponent estimated by the conventional monofractal analyses. However, a comparison of the performance of multifractal analyses with behavioral variables has not yet been addressed. The present study compares the performance of seven multifractal analyses. The multifractal analyses were tested on multiplicative cascading noise that generates time series with a predefined multifractal spectrum and with a structure of variation that mimics intermittent response time variation. Time series with 1,024 and 4,096 samples were generated with additive noise and multiharmonic trends of two different magnitudes (signal-to-noise/trend ratio; 0.33 and 1). The results indicate that all multifractal analysis has individual pros and cons related to sample size, multifractality, and the presence of additive noise and trends in the response time series. The summary of pros and cons of the seven multifractal analyses provides a guideline for the choice of multifractal analyses of response time series and other behavioral variables.     

Aging and intraindividual variability in performance: analyses of response time distributions

It has been suggested that older adults are more variable in their performance because they are more prone to lapses of either attention or intention. In the present experiment, 9 young and 9 older adults each performed nearly 2000 trials of a same-different judgment task. As expected, older adults were slower and more variable than young adults. When the age-related difference in speed was taken into account, however, the older adults were, if anything, less variable than the young adults. When younger and older adults' RT distributions were analyzed using quantile-quantile plots and by fitting ex-Gaussian and Weibull functions, there was no consistent evidence that older adults' distributions were more skewed than young adults', as would be predicted by age-related increases in lapses of attention or intention. Importantly, there was a positive, linear relation between RT and intraindividual variability, and the same relation was observed both within subjects (practice increased speed and reduced variability) as well as between subjects (regardless of age, slower individuals were more variable). Thus, the present results suggest that there may be a general law governing the relation between average RT and variability, and that the greater performance variability of older adults primarily reflects their greater average RTs.     

Reaction time and intelligence: Comparing associations based on two response modes

People who score highly on intelligence tests also tend to have faster and less variable reaction times. Effect size estimates for the reaction time–intelligence association are larger in samples that are more representative of the population. However, such samples have often been tested on a reaction time device that requires reading a number and processing its association with a specific response location (Cox, Huppert, & Whichelow, 1993). Here, we use this device and another reaction time device (Dykiert et al., 2010) that is similar, except that the responses require less processing; subjects simply press a button that is adjacent to the stimulus light. We focus on the possibility that lights as stimuli require less higher-order cognitive engagement than numbers, and then test whether parameters from these two tasks are highly correlated and similarly associated with age and higher cognitive abilities. Both tasks measured simple and choice reaction times and their intra-individual variation across trials. The parameters of the two tasks were very highly correlated and parameters from both tasks were similarly associated with age, social factors, and differences in higher cognitive abilities. The respective choice reaction time parameters from either task accounted for much of the age- and higher cognitive ability-associations of the other task's parameters. These findings are important in establishing that the effect sizes of higher cognitive ability associations with processing speed measures may be found when the processing demands are minimal.     

Inter-hemispheric dynamics revealed by reaction time in the Dimond paradigm

The reminiscence bump is the tendency to recall more autobiographical memories from adolescence and early adulthood than from adjacent lifetime periods. In this online study, the robustness of the reminiscence bump was examined by looking at participants' judgements about the quality of football players. Dutch participants (N?=?619) were asked who they thought the five best players of all time were. The participants could select the names from a list or enter the names when their favourite players were not on the list. Johan Cruijff, Pelé, and Diego Maradona were the three most often mentioned players. Participants frequently named football players who reached the midpoint of their career when the participants were adolescents (mode?=?17). The results indicate that the reminiscence bump can also be identified outside the autobiographical memory domain.     

A systematic, large-scale study of synaesthesia: implications for the role of early experience in lexical-colour associations

For individuals with synaesthesia, stimuli in one sensory modality elicit anomalous experiences in another modality. For example, the sound of a particular piano note may be 'seen' as a unique colour, or the taste of a familiar food may be 'felt' as a distinct bodily sensation. We report a study of 192 adult synaesthetes, in which we administered a structured questionnaire to determine the relative frequency and characteristics of different types of synaesthetic experience. Our data suggest the prevalence of synaesthesia in the adult population is approximately 1 in 1150 females and 1 in 7150 males. The incidence of left-handedness in our sample was within the normal range, contrary to previous claims. We did, however, find that synaesthetes are more likely to be involved in artistic pursuits, consistent with anecdotal reports. We also examined responses from a subset of 150 synaesthetes for whom letters, digits and words induce colour experiences ('lexical-colour' synaesthesia). There was a striking consistency in the colours induced by certain letters and digits in these individuals. For example, 'R' elicited red for 36% of the sample, 'Y' elicited yellow for 45%, and 'D' elicited brown for 47%. Similar trends were apparent for a group of non-synaesthetic controls who were asked to associate colours with letters and digits. Based on these findings, we suggest that the development of lexical-colour synaesthesia in many cases incorporates early learning experiences common to all individuals. Moreover, many of our synaesthetes experienced colours only for days of the week, letters or digits, suggesting that inducers that are part of a conventional sequence (e.g. Monday, Tuesday, Wednesday...; A, B, C...; 1, 2, 3...) may be particularly important in the development of synaesthetic inducer-colour pairs. We speculate that the learning of such sequences during an early critical period determines the particular pattern of lexical-colour links, and that this pattern then generalises to other words.     

Associative symmetry of the memory for object-location associations as revealed by the testing effect

The nature of episodic associations has been subject to a long standing debate, where the two opposing positions postulate associations as either a holistic representation of the constituent elements or as independently modifiable pointers between them. In spite of a history of inconsistent findings, evidence in favour of the theory of symmetric associations has accumulated, yet only for verbal memory [Caplan, J. B., Glaholt, M. G., & McIntosh, A. R. (2006). Linking associative and serial list memory: Pairs versus triples. Journal of Experimental Psychology: Learning, Memory, and Cognition, 32(6), 1244-1265; Kahana, M. J. (2002). Associative symmetry and memory theory. Memory and Cognition, 30(6), 823-840]. Although object-location associations differ in several fundamental characteristics from verbal paired-associates, we recently found associative symmetry in the memory for this class of associations as well [Sommer, T., Rose, M., & Büchel, C. (2007). Associative symmetry vs. independent associations in the memory for object-location associations. Journal of Experimental Psychology: Learning, Memory, and Cognition, 33(1), 90-106]. Due to the inconsistencies in the verbal literature, we felt it to be pertinent to confirm this finding using another experimental approach. Based on recent advances in understanding the effects of successive testing, we were able to make use of this knowledge and introduce this effect as an experimental manipulation in the study of associative symmetry. In particular, we investigated whether the influence of a prior memory test on a subsequent memory test differs when the same or opposite constituent element of an object-location paired-associate cues the retrieval on each test. We observed an identical testing effect for both conditions, which was exclusively driven by reminiscence, the recovery of previously inaccessible information. This finding lends strong support in favour of holistically or symmetrically represented object-location associations and suggests, given the verbal memory literature, a general principle of associative symmetry [Asch, S. E., & Ebenholtz, S. M. (1962). The principle of associative symmetry. Proceedings of the American Philosophical Society, 106, 135-163].     

Changes in self- and object representation as revealed by reflection response

This article considers the three Rorschach tests obtained over an 8-year period for one female patient who struggled around her image of herself and others. Her struggle is revealed in the vicissitudes of the reflection responses over the three testings. A formulation is advanced regarding the meaning and significance of the reflection response as an indication of an emerging self-experience.     

Dynamics of the attentional control of word retrieval: analyses of response time distributions

Since W. Wundt (1904) and H. J. Watt (1906), researchers have found no agreement on how goals direct word retrieval. A prevailing associative account (E. K. Miller & J. D. Cohen, 2001) holds that goals bias association strength, which determines retrieval latency and whether irrelevant words interfere. A symbolic account (A. Roelofs, 2003) holds that goals enable retrieval rules and predicts no strict dependence of interference on latency. Here, 3 chronometric experiments in which the role of relative retrieval latency was investigated through distributional analyses, following Watt, are reported. Participants verbally categorized picture-word pairs that were semantically related or unrelated, or they categorized single pictures or words. The pairs yielded semantic latency effects in both word and picture categorizing, although single words were categorized slower than single pictures. Semantic effects occurred in word categorizing even when postexposure of the pictures compensated for the difference in categorizing latency. Vincentile and ex-Gaussian analyses revealed that the semantic effects occurred throughout the latency distributions, excluding goal neglect as the cause of the effects. The results were interpreted as most consistent with the symbolic account, which was corroborated by computer simulations.     

Covert signs of expectancy in serial reaction time tasks revealed by event-related potentials

Choice reaction time is strongly determined by the sequence of preceding stimuli. With long response-stimulus intervals (RSIs), a cost-benefit pattern is observed, which has been related to expectancy, whereas with short RSIs a benefit-only pattern emerges, possibly because of automatic facilitation. In the present study, event-related potentials were recorded while subjects performed serial choice responses to visual and auditory stimuli at long and short RSIs. As expected, reaction times displayed cost-benefit and benefit-only patterns at long and short RSIs, respectively. In contrast, sequential effects in event-related potential amplitudes displayed a cost-benefit pattern, unaffected by the RSI. The results demonstrate that an expectancy-like mechanism is always active in serial tasks but appears to influence performance only when the RSI is long.     

Attention control and the antisaccade task: a response time distribution analysis

In three experiments response time (RT) differences between correct prosaccade and antisaccade trials were examined via distribution analyses by fitting an ex-Gaussian function to individual RT distributions. Experiment 1 demonstrated that antisaccades are slower than prosaccades and this difference is due to both a shift in the overall distribution as well as a lengthening of the tail of the distribution. Experiment 2 demonstrated that manipulating foreperiod duration led to changes in both accuracy and RT for antisaccades but not prosaccades. Furthermore, the change in RT for antisaccades resulted in a lengthening in the tail of the distribution but not a shift in the distribution. Finally, Experiment 3 demonstrated that with sufficient practice performance on antisaccades was equated with performance on prosaccades in terms of both accuracy and RT. An examination of the RT distributions suggested that practice led to parallel changes in both the mean of the distribution and the tail of the antisaccade distribution. These results are interpreted within a two-factor theory of attention control that suggests that performance on antisaccades is driven by both competition resolution and goal-maintenance abilities.     

Hemispheric processing differences revealed by differential conditioning and reaction time performance.

Two different experimental procedures were used to examine (a) information-processing differences between two groups of subjects (Cs versus Vs) identified by the form of their conditioned eyeblinks; (b) information-processing differences between the right and left cerebral hemispheres; and (c) parallels between hypothesized C-V differences and right-left hemisphere differences. In the first experiment, the evocative command words BLINK and DON'T BLINK served as positive and negative conditioned stimuli. It was found that Vs gave more conditioned eyeblinks than Cs and that differential eyelid conditioning of Vs more than Cs was influenced by the semantic content of the stimuli. More importantly, the conditioning performance of Cs was more influenced by the semantic attributes of the stimuli when they were presented directly to the right visual field (left hemisphere) than when they were presented directly to the left visual field (right hemisphere). In contrast, the conditioning performance of Vs was equally influenced by the semantic attributes regardless of which hemisphere received direct stimulation. A second experiment was designed to determine whether such hemisphere-of-presentation differences for Cs versus Vs could also be obtained in a very different task. Subjects classified as Cs or Vs during a differential eyelid conditioning task then performed two same-different reaction time (RT) tasks that required discrimination of complex polygons in one case and the names of letters in another. On each RT trial both stimuli of a pair appeared briefly either in the center, left, or right visual field. For both Cs and Vs RTs to complex polygon pairs averaged 20 msec faster on left visual field trials than on right visual field trials, consistent with current hypotheses about right-hemisphere specialization for visuospatial processing. In contrast, the results for letter pairs generally confirmed the C-V differences found in Experiment 1. That is, the right visual field (left-hemisphere) advantage for these verbal stimuli was once again larger for Cs than for Vs. The present results suggest that the two groups of subjects (Cs versus Vs) differ qualitatively in the modes of information processing that they typically employ. The results also suggest that these different modes of processing are related to aspects of cerebral hemisphere organization and that even right-handed individuals may differ from each other in the extent to which each cerebral hemisphere is mobilized for a given experimental task. Such individual differences must be incorporated into both models of classical eyelid conditioning and models of cerebral hemisphere specialization.     

Dissociable stages of problem solving (I): temporal characteristics revealed by eye-movement analyses

Understanding the functional neuroanatomy of planning and problem solving may substantially benefit from better insight into the chronology of the cognitive processes involved. Based on the assumption that regularities in cognitive processing are reflected in overtly observable eye-movement patterns, here we recorded eye movements while participants worked on Tower of London (TOL) problems that comprised an experimental manipulation of different task demands. Single-trial saccade-locked analyses revealed that higher demands on forming an internal problem representation were associated with an increased number of gaze alternations between start state and goal state, but did not show any effect on the durations of these inspections of the states. In contrast, higher demands on actual planning in terms of mental manipulations of working memory contents coincided with a prolonged duration of the very last inspection of the start state (i.e., immediately preceding movement execution) but did not show any effect on the number of gaze alterations. Differential task demands on internalization and planning processes during problem solving hence selectively affect different eye-movement parameters. Moreover, these findings complement previous neuroimaging data on dissociable contributions of left and right dorsolateral prefrontal cortex in problem solving with novel evidence for a corresponding dissociation in the eye-movement patterns reflecting the associated cognitive processes.     

Response-specific slowing in older age revealed through differential stimulus and response effects on P300 latency and reaction time

Older age produces numerous changes in cognitive processes, including slowing in the rate of mental processing speed. There has been controversy over the past three decades about whether this slowing is generalized or process-specific. A growing literature indicates that it is process-specific and suggests it is most dramatic at the interface where a stimulus input is translated into a response output. We tested this hypothesis using a task in which young and older adult males made either compatible or incompatible responses to the word LEFT or RIGHT shown briefly and variously located in a 4 row × 6 column matrix surrounded by # signs or by letters chosen randomly from the sets A-G or A-Z. Processing speed was measured using P300 latency and reaction time. Experimental effects on these two measures provided support for the hypothesis in revealing that stimulus identification processes were preserved, whereas processes related to translating a stimulus input into a designated response output and then selecting that response were compromised in the elderly.