Sensory-modality opinion scales for individual subjects

In two sessions each, 16 subjects were asked to match apparent handgrip force and apparent duration in a counterbalanced order to the pronounceability of 12 trigrams in order to assess sensory modality opinion scales for individuals. Scales for individuals, like those for group data, were consistent across tasks and showed reliability across sessions. Subjects displayed strong agreement on the relative pronounceabilities of the trigrams according to Kendall’s test for concordance. A significant intersession correlation for subjects’ multimodality exponents indicated reliable differences in these exponents among individuals. Comparisons with psychophysical scales were made and discussed.     

Individual differences in power functions for a 1-week intersession interval

Two experiments examined correlations of the power function exponents of individual Ss obtained in each of two sessions. Half the Ss for any task performed second sessions immediately after the first, the other half after a week’s delay. In Experiment I, groups of 16 Ss gave magnitude estimations of apparent area, or else of area and loudness. In Experiment II, groups of 16 Ss made cross-modality matches of apparent time duration to area. Significant correlations in all cases indicated consistent and persisting S differences in exponents. The results are related to the findings of other studies of such individual differences.     

Intraindividual consistencies in cross-modal matching across several continua

To determine the relationship between individual exponents for cross-modal stimulus matches for both directions of matching, and to assess the transitivity of individual exponents, subjects were asked to adjust both the judgment and criterion stimuli. Experiment 1 involved four continua paired in 12 ordered combinations; Experiment 2 involved five continua and 20 ordered combinations. Two subjects served in each experiment. The individual exponent of the power function for matches of A to B was close to the inverse of the exponent for matches of B to A, but there was systematic deviation, indicating the presence of a small regression effect. Transitivity of individual exponents was determined by forming ratios of exponents from matches involving other continuum pairs to predict obtained exponents; the means of the distribution of deviations of obtained from predicted values was ?.02 log units, and the standard deviation was .15 log units, indicating that, on the average, predicted values were close to obtained exponents—that is, transitivity of exponents holds for individuals.     

Consistency of individual exponents in cross-modal matching

An important question about individual differences in the exponent of the psychophysical power law is how they should be interpreted. The differences may reflect permanent characteristics of individuals, and it has been argued that, if this is so, the range of these differences is so great as to identify the class of data as exceptional among the physical and biological sciences. Cited as evidence of such permanence has been the correlation between individual exponents obtained on two separate occasions. In a previous paper, we showed that increasing the time interval between occasions reduced the correlation to a nonsignificant level; we argued, therefore, that obtained individual differences in exponents, even though large, depended upon the operation of factors only incidentally associated with the particular observer. In a series of new studies of session-to-session correlation between individual exponents, we provide evidence that: (1) our original finding for magnitude estimates of visual size is repeatable, with the correlation dropping to nearly zero after 1 week; (2) when judged line length is matched to brightness, a delay of I week is sufficient to produce a nonsignificant correlation; (3) in contrast, magnitude estimates of loudness yield significant correlations after a week’s delay; (4) but, when moduli are arbitrarily changed between sessions by the experimenter, these correlations for magnitude estimates of loudness drop to a nonsignificant level, even for a zero-delay condition. We conclude that, whereas in some scaling tasks the passage of time alone between sessions is sufficient to disrupt what appears to be the mnemonic basis for session-to-session correlation, in other (less familiar) tasks, more positive interference (in the form of a modulus change) is needed to achieve the same end. The evidence is consistent with the belief that enduring characteristics of the observer contribute only a small portion of the variability in individual power law exponents.     

How repeatable are Stevens’s power law exponents for individual subjects?

Magnitude estimations of apparent length and apparent area were obtained for the same group of Ss over successive experimental sessions. Session-to-session correlations between individual exponents on a given continuum were positive and reliable for successive 24-h intersession intervals, but were not significant for a 1-year interval. In a second experiment on judgments of apparent area, when each stimulus was judged only once per session, the session-to-session correlation was reliable only when the intersession interval was zero. Six other intervals, ranging from 1 to 77 days, yielded nonsignificant correlations. When the constraints exerted by repeated judging are removed, the location of S’s exponent in a distribution of exponents is stable only for brief intervals. Thus the differences among exponents cannot reflect any persisting attributes of Ss’ sensory or judgmental processes.     

Constancy of individual exponents for category production of inspired lung volume

Individual exponents for production of inspired lung volume were compared both within experimental sessions (after a delay of 5 to 10 min.) and between sessions (after a delay of 1 yr.). Reliable correlations were observed between pairs of individual exponents regardless of the time elapsed between repetitions of the task. Constancy of exponents may reflect a propensity for subjects to respond in characteristic ways to psychophysical scaling tasks.     

Temporal precision in tapping and circle drawing movements at preferred rates is not correlated: further evidence against timing as a general-purpose ability

Recently, researchers have discovered that individuals who are consistent timers in a tapping task are not necessarily consistent timers when they perform a continuous drawing task. In other words, nonsignificant correlations were found among tapping and drawing movements for timing precision (S. D. Robertson et al., 1999). In the present experiment, the authors investigated whether or not consistency in timing for tapping and drawing was correlated when participants (N = 24) were allowed to move at their preferred rate of movement. There were no significant correlations between tapping and drawing in terms of timing precision. That result lends further support to the notion that timing behavior is specific to the nature of the task, and thus further weakens the idea that timing is a generalized ability that can be imposed on a variety of different types of tasks.     

Temporal Precision in Tapping and Circle Drawing Movements at Preferred Rates is Not Correlated: Further Evidence Against Timing as a General-Purpose Ability

Recently, researchers have discovered that individuals who are consistent timers in a tapping task are not necessarily consistent timers when they perform a continuous drawing task. In other words, nonsignificant correlations were found among tapping and drawing movements for timing precision (S. D. Robertson et al., 1999). In the present experiment, the authors investigated whether or not consistency in timing for tapping and drawing was correlated when participants (N = 24) were allowed to move at their preferred rate of movement. There were no significant correlations between tapping and drawing in terms of timing precision. That result lends further support to the notion that timing behavior is specific to the nature of the task, and thus further weakens the idea that timing is a generalized ability that can be imposed on a variety of different types of tasks.     

Limitations to the spacing effect: demonstration of an inverted u-shaped relationship between interrepetition spacing and free recall

The spacing effect refers to the finding that memory for repeated items improves when the interrepetition interval increases. To explain the spacing effect in free-recall tasks, a two-factor model has been put forward that combines mechanisms of contextual variability and study-phase retrieval (e.g., Raaijmakers, 2003; Verkoeijen, Rikers, & Schmidt, 2004). An important, yet untested, implication of this model is that free recall of repetitions should follow an inverted u-shaped relationship with interrepetition spacing. To demonstrate the suggested relationship an experiment was conducted. Participants studied a word list, consisting of items repeated at different interrepetition intervals, either under incidental or under intentional learn instructions. Subsequently, participants received a free-recall test. The results revealed an inverted u-shaped relationship between free recall and interrepetition spacing in both the incidental-learning condition and the intentional-learning condition. Moreover, for intentionally learned repetitions, the maximum free-recall performance was located at a longer interrepetition interval than for incidentally learned repetitions. These findings are interpreted in terms of the two-factor model of spacing effects in free-recall tasks.     

Psychophysical scales of the olfactory pleasantness of homologous alcohols

A category, a ratio estimation, and three magnitude scales were constructed from the observations of 10 Os who judged the pleasantness of a homologous series of n-aliphatic alcohols. Magnitude scaling indicated that pleasantness generally varies inversely with chain length, which is consistent with the findings of earlier investigators who used different methods; ratio estimation also indicated an inverse relationship. Stable magnitude scales resembled power functions with exponents of ?0.262 to ?0.587; the adjusted ratio estimation’s was ?0.138. Pleasantness seemed to be unexpectedly prothetic, some evidence of which had also been reported in an earlier study involving a more diverse set of odorants. Yet in the present study the hedonic range was small and in the earlier, large. More than the size of range appears to account for the puzzling prothetic evidence.     

Stability and consistency of children’s event recall

The purpose of the study was to investigate consistency of recall across different tasks of event recall (similar to eyewitness tasks) and stability of performance across two different events. Additionally, developmental differences in consistency and stability were explored. 6-, 8-, and 10-year-old children were subsequently shown two different events (videos) and were questioned about each event in two separate interviews. For both videos, performance levels in free recall, unbiased cued recall, and suggestibility were at similar levels, with older children generally outperforming younger children. As to intertask consistency of recall, there were significant correlations between correct free recall and correct unbiased cued recall but not between correct free recall and yielding to suggestive questions. All three measures of eyewitness performance showed significant group stability (test-retest correlations) across the two interviews, regardless of age. However, individual stability (lability) was lower, which points to moderate individual differences in stability across the two interviews. The findings are discussed in terms of underlying cognitive skills and the problem of predicting a single child’s memory performance in real cases of eyewitness testimony.     

Population norms of top sensory magnitudes and S. S. Stevens’ exponents

If S. S. Stevens’ exponents indicate the rates at which sensations grow with increases in sensory intensity, they ought to correlate with the population norms of top sensory magnitudes. Using a comprehensive sample of eight sensory dimensions, the tau coefficient of rank correlation between Stevens’ exponents and the medians of the top sensory magnitudes reported by 305 observers was found to be only +.15 (p>05). With the geometric means tau fell to ?.04. A split-half consistency check on the medians of the population norms suggested that they were not to blame for the low correlation. Direct comparisons of pairs of sensory dimensions on 146 additional observers produced results which confirmed the population norms. Since there is no way of comparing most of the top physical stimuli experienced in everyday life, it is not possible to make a joint prediction from exponents and top stimuli. S. S. Stevens’ exponents thus appear to have little predictive value outside the experimental conditions under which they were measured.     

Individual differences in the verbal coding of familiar visual stimuli

Two experiments were performed both of which involved the same-different comparison of pairs of alphabet letters. "Same" reaction times were obtained for both physical matches (e.g., AA) and name matches (e.g., aA). The results of both experiments supported the hypothesis that individual subjects would differ with respect to whether or not they based their physical matches on a comparison of verbal codes. In Experiment I, subjects differed in the size of their reaction time difference between physical and name matches, and in Experiment II, individuals differed with respect to whether or not the frequency of usage of the letters affected their reaction time for physical matches. In both experiments, the individual differences in verbally coding physical matches were related to Hock's (1973) individual differences distinction between subjects emphasizing analytic processes and subjects emphasizing structural processes.     

Judgments of differences and ratios of numerals

Each subject performed two tasks, dividing a line segment so that either (a) theratio of subjective lengths corresponded to the ratio of the magnitudes of two numerals or (b) thedifference in length was proportional to the numerical difference. Had subjects actually performed two operations on the same scale, the responses would have been nonmonotonically related. Instead, data for the two tasks were nearly identical and ordinally compatible with either a ratio or a subtractive model. The ratio model implied scale values for numerals that were a positively accelerated function of numerical value, inconsistent with previous results. With a nonlinear response function for graphic length, the subtractive model fit well, yielding scale values that were a negatively accelerated function of numerical value and a linear function of previously obtained scales. These results, together with other recent findings, suggest that subjects may perform the same operation in spite of instructions to judge “ratios” or “differences” and that this operation can be best represented by a subtractive model.     

Subject differences in cross-modality matching

Forty-eight Ss performed four tasks each: (1) magnitude estimation of area, (2) magnitude estimation of numerousness, (3) cross-modality matching of force of handgrip to area, and (4) cross-modality matching of force of handgrip to numerousness. An additional 48 Ss performed Tasks 2 and 4. Psychophysical power functions were fitted to the data of each S for each condition. Higher correlations between individual exponents were found for conditions employing a common response (i.e., estimating or squeezing) than were found for conditions with the same set of stimuli. Individual differences among exponents stem more from the idiosyncratic use of the dependent variable than from different sensory characteristics.     

Thinking aloud performance: Individual consistencies over tasks

Previous research (Gilhooly, 1987) indicated considerable individual consistency in quantity and quality of thinking aloud performance over three 8-puzzle tasks. The present study investigated the consistency of individual thinking aloud performance over two types of tasks. One type was largely spatial (the 8-puzzle) and the other largely verbal (the Poisoned Foods task). Considerable individual consistency in thinking aloud performance was found within each task type and, more importantly, between types of task. Thus, subjects who produced lengthy and complete protocols on the 8-puzzle problems also did so in the Poisoned Foods task. These results are discussed in the context of Ericsson and Simon’s (1984) model of thinking aloud.     

Binaural summation after learning psychophysical functions for loudness

Do response-related processes affect perceptual processes? Sometimes they may: Algom and Marks (1990) produced different loudness exponents by manipulating stimulus range, and thereby also modified the rules of loudness summation determined by magnitude scaling. The present study manipulated exponents by having a dozen subjects learn prescribed power functions with exponents of 0.3, 0.6, or 1.2 (re sound pressure). Subjects gave magnitude estimates of the loudness of binaural signals during training, and of monaural and binaural signals after training. During training, subjects’ responses followed the nominal functions reasonably well. Immediately following training, subjects applied the numeric response scales uniformly to binaural and monaural signals alike; the implicit monaural-binaural loudness matches, and thus the basic rules underlying binaural summation, were unaffected by the exponent learned. Comparison of these results with those of Algom and Marks leads us to conclude that changing stimulus range likely influences underlying perceptual events, whereas “calibrating” a loudness scale through pretraining leaves the perceptual processes unaffected.     

Testing problem-solving capacities: differences between individual testing and social group setting

Testing animals individually in problem-solving tasks limits distractions of the subjects during the test, so that they can fully concentrate on the problem. However, such individual performance may not indicate the problem-solving capacity that is commonly employed in the wild when individuals are faced with a novel problem in their social groups, where the presence of a conspecific influences an individual’s behaviour. To assess the validity of data gathered from parrots when tested individually, we compared the performance on patterned-string tasks among parrots tested singly and parrots tested in social context. We tested two captive groups of orange-winged amazons (Amazona amazonica) with several patterned-string tasks. Despite the differences in the testing environment (singly vs. social context), parrots from both groups performed similarly. However, we found that the willingness to participate in the tasks was significantly higher for the individuals tested in social context. The study provides further evidence for the crucial influence of social context on individual’s response to a challenging situation such as a problem-solving test.     

Thinking aloud performance: Individual consistencies over tasks

Previous research (Gilhooly, 1987) indicated considerable individual consistency in quantity and quality of thinking aloud performance over three 8-puzzle tasks. The present study investigated the consistency of individual thinking aloud performance over two types of tasks. One type was largely spatial (the 8-puzzle) and the other largely verbal (the Poisoned Foods task). Considerable individual consistency in thinking aloud performance was found within each task type and, more importantly, between types of task. Thus, subjects who produced lengthy and complete protocols on the 8-puzzle problems also did so in the Poisoned Foods task. These results are discussed in the context of Ericsson and Simon’s (1984) model of thinking aloud.     

Aging and Individual Variation in Interhemispheric Collaboration and Hemispheric Asymmetry

ABSTRACT

Thirty younger (Mean Age = 19.9 years) and 20 older adults (Mean Age = 74.7 years) performed Physical and Name Identity letter-matching tasks (matches were either within or between hemispheres) to study age-related changes in 1) the efficiency with which the two hemispheres interact with each other and 2) hemispheric asymmetry. In order to determine whether age-related effects were associated with differences in cognitive resources, the same individuals completed a set of memory span tasks. Performance on the letter-matching tasks indicated that the costs of interhemispheric collaboration were greater for older than for younger participants. However, within the older group, the advantage of spreading processing across both hemispheres increased as memory span decreased, suggesting that older individuals who are challenged by cognitive complexity are more likely to show increased benefits from between-hemisphere processing than individuals who are not so challenged. There was also an overall left visual field/right hemisphere advantage for the younger but not for the older group, suggesting greater age-related declines in right- than left-hemisphere function.