Magnitude scales for cold pressor pain

Subjects in two experiments immersed a hand and forearm in ice water (cold pressor test) for 60 sec and gave magnitude estimates of pain every 5 sec. Forty subjects immersed an arm for three trials in Experiment 1, and 60 subjects immersed an arm for two trials in Experiment 2. Linear, power, or additive constant functions fitted the data almost equally well. Exponents of the two-constant power function differed from those of the additive constant function. Individual differences in exponents were marked, but various psychological manipulations aimed at reducing pain failed to affect the exponents. The utility of power functions to describe cold pressor pain has yet to be determined.     

Adaptive decision processes in perceptual comparisons: effects of changes in the global difficulty context

Adaptive decision processes were investigated in experiments involving an unexpected change in the global ease or difficulty of the task. Under accuracy stress, a shift from an easy to a difficult context induced a marked increase in decision time, but a shift from a difficult to an easy context did not. Under speed stress, a shift to a more difficult context induced lower accuracy and rated confidence, depending on the difficulty of the decisions. A view of caution developed in D. Vickers's (1979) accumulator theory--whereby one seeks to base decisions on more information--is compared with a view based on slow and fast guessing theory (W. M. Petrusic, 1992; W. M. Petrusic & J. V. Baranski, 1989a)--whereby one seeks to base decisions on more diagnostic information. On balance, the findings support the latter view.     

Resolution time and the coding of arithmetic relations on supraliminally different visual extents

Comparison time for pairs of vertical-line stimuli, sufficiently different that they can be errorlessly discriminated with respect to visual extent, was examined as a function of arithmetic relations (physical ratio and difference) on members of the pair. Arithmetic relations are coded very precisely by judgment time: Responses slow as stimulus ratios approach one with difference fixed, and as stimulus differences approach zero with ratio fixed. Most models which assume a simple (Difference or Ratio) resolution rule operating on independent sensations require judgment time to depend on either ratios or on differences but not on both. Further tests showed both an index based on median judgment times and a confusion index based on pairs of observed judgment times, satisfied the requirements for a Positive Difference Structure. One representation of these data, which remains acceptable through all analyses, is a Difference resolution rule operating on sensations determined by a power psychophysical function with β < 1. Specifically, L(x, y) = F{ψ(x) ? ψ(y)} + R, where L(x, y) is the judgment time with the stimulus pair x and y, ψ(x) = Ax^β + C, R is a positive constant, and F is a continuous monotone decreasing function.     

Selective attention and subjective confidence calibration

In the present experiments, failures of selective visual attention were invoked using the B. A. Eriksen and C. W. Eriksen (1974) flanker task. On each trial, a three-letter stimulus array was flashed briefly, followed by a mask. The identity of the two flanking letters was response congruent, neutral, or incongruent with the identity of the middle target letter. On half of the trials, confidence ratings were obtained after each response. In the first three experiments, participants were highly overconfident in the accuracy of their responding to incongruent flanker stimulus arrays. In a final experiment, presenting a prestimulus target location cue greatly reduced both selective attention failure and overconfidence. The findings demonstrate that participants are often unaware of such selective attention failures and provide support for the notion that, in these cases, decisional processing is driven largely by the identities of the incongruent flankers. In addition, responding was invariably slower and sometimes more accurate when confidence was required than when it was not required, demonstrating that the need to provide posttrial confidence reports can affect decisional processing. Moreover, there was some evidence that the presence of neutral contextual flanking information can slow responding, suggesting that such nondiagnostic information can, indeed, contribute to decisional processing.     

Remembered instructions with symbolic and perceptual comparisons

Semantic congruity effects (SCEs) were obtained in each of two experiments, one with symbolic comparisons and the other with comparisons of visual extents. SCEs were reliably larger when the instructions indicating the direction of the comparison were represented by consonant-vowel-consonant (CVC) nonsense syllables, which had been associated with the conventional instructions in a preliminary learning phase of the experiment. Enhanced SCEs with the CVC instructions were evident, especially when stimulus pair location and instruction direction did not match. This finding is not readily explained by any non-evidence-accrual theories of the SCE (e.g., expectancy, semantic coding, and reference point) or by their accrual-based extensions. On the other hand, the general class of evidence-accrual views of SCEs, such as those developed in Leth-Steensen and Marley (2000) and in Petrusic (1992), receive considerable empirical support when the locus of the SCE is specified in terms of the congruency of stimulus pair location and the direction of the instruction.     

Realism of confidence in sensory discrimination

Is there a common and general basis for confidence in human judgment? Recently, we found that the properties of confidence judgments in the sensory domain mirror those previously established in the cognitive domain; notably, we found underconfidence on easy sensory judgments and overconfidence on hard sensory judgments. In contrast, data from the Uppsala laboratory in Sweden suggest that sensory judgments are unique; they found a pervasive underconfidence bias, with overconfidence being evident only on very hard sensory judgments. Olsson and Winman (1996) attempted to resolve the debate on the basis of methodological issues related to features of the stimulus display in a visual discrimination task. A reanalysis of the data reported in Baranski and Petrusic (1994), together with the findings of a new experiment that controlled stimulus display characteristics, supports the position that the difference between the Canadian and the Swedish data is real and, thus, may reflect cross-national differences in confidence in sensory discrimination.     

Relational judgments with remembered stimuli

Two experiments investigating the effect of the direction of a relational judgment on the speed of the judgment are reported. In both experiments, college students required more time to select the smaller of a pair of large animals than to select the larger. Conversely, the smaller of a pair of small animals was selected more quickly than was the larger. The magnitude of this “cross-over effect” was fully graded, increasing regularly with extremity, but the variability of the response times in each direction was unrelated to extremity. Individual animals were classified as “small” or “large” with almost perfect consistency. This pattern of results is used to evaluate several models of relational judgment; of these, the congruency model is shown to be inconsistent with these data.

     

Similarity comparisons with remembered and perceived magnitudes: Memory psychophysics and fundamental measurement

At the outset, subjects learned to associate a label with each element in a set of perceptual magnitudes (visual extents), using traditional paired-associate learning methods. Subsequently, on some trials, subjects indicated which pair of two pairs of labels corresponded to the more similar perceptual referents, and, on other trials, they selected the more dissimilar pair. It is shown that these similarity comparisons satisfy the axioms (transitivity and intradimensional subtractivity) necessary to conclude that they are based on computation of the difference of the differences of analogue-based interval scale representations.The findings also permitted refutation of the idea that memory for elementary percepts arises from their reperception. Notably, the memory exponent was 0.697, but the perception exponent was 0.546, and the reperception idea requires that the memory exponent be the square of the perception exponent (0.546²=0.298). Symbolic distance effects and enhanced response time-based semantic congruity effects, typically found with binary comparisons, extend the range of commonalties found between perceptual and memory psychophysics.     

Long-term memory for elementary visual percepts: memory psychophysics of context and acquisition effects

In the first phase of each of two experiments, participants learned to associate a set of labels (i.e., consonant-vowel-consonant [CVC]) with a set of line lengths by using a paired-associate learning procedure. In the second phase of each experiment, these learned labels were used as memorial standards in the method of constant stimuli. Psychometric functions and the associated indices of discriminative performance (i.e., Weber fractions [WFs], just noticeable difference, and point of subjective equality) were then obtained for the remembered standards. In Experiment 1, WFs (i.e., the indices of memory precision) obtained with remembered standards were found to be higher (i.e., had poorer discriminability) than were WFs obtained with perceptual standards. In addition, WFs obtained with the remembered standards exhibited serial position effects (i.e., poorer discriminability for central items in the memory ensemble) and systematically varied with set size (i.e., the number of standards in the memory set), but WFs obtained with perceptual standards did not depend on serial position or set size. In Experiment 2, increasing the number of acquisition trials reduced WFs and diminished serial position effects. In addition, WFs did not vary systematically with the "physical" spacing between the standards in memory, but they did with the ordinal spacing. The results are consistent with a noisy analogue representation of remembered magnitudes, whereby central items in a memory ensemble are subject to lateral inhibition and thus reduced discriminability. Finally, presentation order effects, as defined by the classic time-order error, were observed with purely perceptual comparisons but not with comparisons involving a remembered standard. This latter finding is inconsistent with a strong form of the functional equivalence view of perception and memory.