Attentional scanning and space errors

Analogous cognitive strategies for tactile learning in the rodent and human brain

Evolution has molded individual species' sensory capacities and abilities. In rodents, who mostly inhabit dark tunnels and burrows, the whisker-based somatosensory system has developed as the dominant sensory modality, essential for environmental exploration and spatial navigation. In contrast, humans rely more on visual and auditory inputs when collecting information from their surrounding sensory space in everyday life. As a result of such species-specific differences in sensory dominance, cognitive relevance and capacities, the evidence for analogous sensory-cognitive mechanisms across species remains sparse. However, recent research in rodents and humans yielded surprisingly comparable processing rules for detecting tactile stimuli, integrating touch information into percepts, and goal-directed rule learning. Here, we review how the brain, across species, harnesses such processing rules to establish decision-making during tactile learning, following canonical circuits from the thalamus and the primary somatosensory cortex up to the frontal cortex. We discuss concordances between empirical and computational evidence from micro- and mesoscopic circuit studies in rodents to findings from macroscopic imaging in humans. Furthermore, we discuss the relevance and challenges for future cross-species research in addressing mutual context-dependent evaluation processes underpinning perceptual learning.

Tests of the abilities to judge ratios of extensive and intensive sensory magnitudes

The assumption that people are able to numerically judge ratios of sensory magnitude is often used to scale sensations. In this study, we tested this assumption for the extensive sensation of length and the intensive sensations of heaviness and brightness. A ratio model fit judged length ratios accurately and fit judged heaviness and brightness ratios inaccurately. Also, most participants could not judge brightness ratios, even if they seemed able to respond nonverbally to the brightness ratios. These results suggest that people may generally be able to judge extensity ratios but not intensity ratios. Participants used auxiliary judgment operations to compensate for their lack of ability to judge intensity ratios. These auxiliary, nonratio operations were found to yield linear scales of intensive sensory magnitude.

The Indecision Model of Psychophysical Performance in Dual-Presentation Tasks: Parameter Estimation and Comparative Analysis of Response Formats

Psychophysical data from dual-presentation tasks are often collected with the two-alternative forced-choice (2AFC) response format, asking observers to guess when uncertain. For an analytical description of performance, psychometric functions are then fitted to data aggregated across the two orders/positions in which stimuli were presented. Yet, order effects make aggregated data uninterpretable, and the bias with which observers guess when uncertain precludes separating sensory from decisional components of performance. A ternary response format in which observers are also allowed to report indecision should fix these problems, but a comparative analysis with the 2AFC format has never been conducted. In addition, fitting ternary data separated by presentation order poses serious challenges. To address these issues, we extended the indecision model of psychophysical performance to accommodate the ternary, 2AFC, and same-different response formats in detection and discrimination tasks. Relevant issues for parameter estimation are also discussed along with simulation results that document the superiority of the ternary format. These advantages are demonstrated by fitting the indecision model to published detection and discrimination data collected with the ternary, 2AFC, or same-different formats, which had been analyzed differently in the sources. These examples also show that 2AFC data are unsuitable for testing certain types of hypotheses. matlab and R routines written for our purposes are available as Supplementary Material, which should help spread the use of the ternary format for dependable collection and interpretation of psychophysical data.

Mental-Rotation Effect: A Function of Elementary Stimulus Discriminability?

It is well known that when humans have to decide whether two differently oriented shapes are identical or mirror images their performance deteriorates as a function of the orientation disparity (mental-rotation effect). Here it is shown that the effect can also be obtained reliably with non-mirror-image, arbitrarily different polygons provided they are previously selected to be hard to discriminate. The slope of the decision speed versus orientation disparity functions was found to be inversely related to the discriminability of shapes under conditions of no, ie 0°, orientation disparity. Easily discriminable polygon pairs yielded essentially flat, no-effect functions. The arbitrary polygons that were more difficult to discriminate produced a rotation effect that was similar to those of mirror-image polygon pairs. Mirror images in this context may only be a special case of hard-to-discriminate stimuli. We also show that the speed of judging whether simple lines were of the same or different length was similarly subject to a rotation effect provided that the length differences were sufficiently small, ie when their baseline dicriminability was poor enough. It is suggested that the mental rotation of complex shapes (eg polygons) may build on rotation effects pertaining to the simpler elements of which they are composed. Further, some special effects associated with the rotation of such simpler components may explain certain peculiarities apparent in orientation invariance functions obtained with complex stimuli.

The Instructional Dependency of SNARC Effects Reveals Flexibility of the Space-Magnitude Association of Nonsymbolic and Symbolic Magnitudes

The Spatial-Numerical Association of Response Codes (SNARC) effect refers to the phenomenon that small versus large numbers are responded to faster in the left versus right side of space, respectively. Using a pairwise comparison task, Shaki et al. found that task instruction influences the pattern of SNARC effects of certain types of magnitudes which are less rigid in their space-magnitude association .The present study examined the generalizability of this instruction effect using pairwise comparison of nonsymbolic and symbolic stimuli within a wide range of magnitudes. We contrasted performance between trials in which subjects were instructed to select the stimulus representing the smaller versus larger magnitude within each pair. We found an instruction-dependent pattern of SNARC effects for both nonsymbolic and symbolic magnitudes. Specifically, we observed a SNARC effect for the “Select Smaller” instruction, but a reverse SNARC effect for the “Select Larger” instruction. Considered together with previous studies, our findings suggest that nonsymbolic magnitudes and relatively large symbolic magnitudes have greater flexibility in their space-magnitude association.

Beware how you compare: comparison direction dictates stimulus-valence-modulated presentation-order effects in preference judgment

Englund and Hellström (Journal of Behavioral Decision Making 25:82-94, 2012a) found a tendency to prefer the left (first-read) of two attractive alternatives but the right (second-read) of two unattractive alternatives-a valence-dependent word-order effect (WOE). They used stimulus pairs spaced horizontally, and preference was indicated by choosing one of several written statements (e.g., "apple I like more than pear"). The results were interpreted as being due to stimulus position, with the magnitude of the left stimulus having a greater impact on the comparison outcome than the magnitude of the right. Here we investigated the effects of the positioning of the stimuli versus the semantics of the response alternatives (i.e., comparison direction) on the relative impacts of the stimuli. Participants rated preferences for stimuli spaced horizontally with the response alternatives not dictating a comparison direction (Exp. 1), and stimuli spaced vertically using Englund and Hellström's (Journal of Behavioral Decision Making 25:82-94, 2012a) response alternatives, which dictate a comparison direction semantically (Exp. 2). The results showed that the valence-dependent WOE found by Englund and Hellström (Journal of Behavioral Decision Making 25:82-94, 2012a) was not due to the horizontal stimulus positioning per se, but to the induced comparison direction, with the effect probably being mediated by attention directed at the subject of the comparison. We concluded that a set comparison direction is required for the valence-dependent WOE to appear, and that using Hellström's sensation-weighting model to determine stimulus weights is a way to verify the comparison direction.

The human somatosensory system: from perception to decision making

Pioneering human and animal research has yielded a better understanding of the brain networks involved in somatosensory perception and decision making. New methodical achievements in combination with computational formalization allow research questions to be addressed which increasingly reflect not only the complex sensory demands of real environments, but also the cognitive ones. Here, we review the latest research on somatosensory perception and decision making with a special focus on the recruitment of supplementary brain networks which are dependent on the situation-associated sensory and cognitive demands. We also refer to literature on sensory-motor integration processes during visual decision making to delineate the complexity and dynamics of how sensory information is relayed to the motor output system. Finally, we review the latest literature which provides novel evidence that other everyday life situations, such as semantic decision making or social interactions, appear to depend on tactile experiences; suggesting that the sense of touch, being the first sense to develop ontogenetically, may essentially support later development of other conceptual knowledge.

Presentation-order effects for aesthetic stimulus preference

For preference comparisons of paired successive musical excerpts, Koh (American Journal of Psychology, 80, 171-185, 1967) found time-order effects (TOEs) that correlated negatively with stimulus valence-the first (vs. the second) of two unpleasant (vs. two pleasant) excerpts tended to be preferred. We present three experiments designed to investigate whether valence-level-dependent order effects for aesthetic preference (a) can be accounted for using Hellström's (e.g., Journal of Experimental Psychology: Human Perception and Performance, 5, 460-477, 1979) sensation-weighting (SW) model, (b) can be generalized to successive and to simultaneous visual stimuli, and (c) vary, in accordance with the stimulus weighting, with interstimulus interval (ISI; for successive stimuli) or stimulus duration (for simultaneous stimuli). Participants compared paired successive jingles (Exp. 1), successive color patterns (Exp. 2), and simultaneous color patterns (Exp. 3), selecting the preferred stimulus. The results were well described by the SW model, which provided a better fit than did two extended versions of the Bradley-Terry-Luce model. Experiments 1 and 2 revealed higher weights for the second stimulus than for the first, and negatively valence-level-dependent TOEs. In Experiment 3, there was no laterality effect on the stimulus weighting and no valence-level-dependent space-order effects (SOEs). In terms of the SW model, the valence-level-dependent TOEs can be explained as a consequence of differential stimulus weighting in combination with stimulus valence varying from low to high, and the absence of valence-level-dependent SOEs as a consequence of the absence of differential weighting. For successive stimuli, there were no important effects of ISI on weightings and TOEs, and, for simultaneous stimuli, duration had only a small effect on the weighting.

Prior Information biases stimulus representations during vibrotactile decision making

Neurophysiological data suggest that the integration of prior information and incoming sensory evidence represents the neural basis of the decision-making process. Here, we aimed to identify the brain structures involved in the integration of prior information about the average magnitude of a stimulus set and current sensory evidence. Specifically, we investigated whether prior average information already biases vibrotactile decision making during stimulus perception and maintenance before the comparison process. For this purpose, we used a vibrotactile delayed discrimination task and fMRI. At the behavioral level, participants showed the time-order effect. This psychophysical phenomenon has been shown to result from the influence of prior information on the perception of and the memory for currently presented stimuli. Similarly, the fMRI signal reflected the integration of prior information about the average vibration frequency and the currently presented vibration frequency. During stimulus encoding, the fMRI signal in primary and secondary somatosensory (S2) cortex, thalamus, and ventral premotor cortex mirrored an integration process. During stimulus maintenance, only a region in the intraparietal sulcus showed this modulation by prior average information. Importantly, the fMRI signal in S2 and intraparietal sulcus correlated with individual differences in the degree to which participants integrated prior average information. This strongly suggests that these two regions play a pivotal role in the integration process. Taken together, these results support the notion that the integration of current sensory and prior average information is a major feature of how the human brain perceives, remembers, and judges magnitude stimuli.

Voluntary visual attention and phenomenal line length

In 1956, Fraisse, et al. reported subjects judged that lines were longer when voluntary attention was focused on the lines than when attention was distracted from the lines. In the many attempts to repeat these results, none has ascertained whether attention on reported line length was a phenomenal effect. In the present study, 46 subjects were shown as stimuli pairs of horizontal or vertical briefly flashed lines with a fixation cross placed equidistant between the lines but far from each one. A change in color of one arm of the cross was used as a cue to focus subjects' voluntary attention on one line. Analysis showed attention increased the judged length of attended lines. Since this effect of attention also occurred when subjects were absolutely certain they saw the stimulus lines differed in length, this effect indicates that attention increased the phenomenal length of the attended lines. This lengthening was quite small: it involved a maximum mean increase of about .15 in the probability of the comparative response that the attended line was longer. This effect occurred in the horizontal dimension and was almost absent in the vertical dimension. In agreement with data indicating that flashed lines expand phenomenally by activating motion detectors and that focused attention makes neural motion responses increase in amplitude, the present results suggest that focused attention makes attended lines look longer because it makes these lines expand phenomenally more rapidly.

Attention and Perception, Memory, and Judgment of Line Length

The literature reports that focused attention alters perceived length of lines. Some tests of this attentional effect require that subjects compare line lengths. This note shows that conceptual confusions inherent in this comparison make the tests invalid.

Comparison is not just subtraction: Effects of time- and space-order on subjective stimulus difference

In five experiments, participants made comparative judgments of paired successive or simultaneous stimuli. Time- or space-order errors were obtained, which varied with the interstimulus interval (ISI) or stimulus duration, as well as with the stimulus level. The results, in terms of scaled subjective differences, are well described by Hellström's (1979) sensation-weighting model. With successive presentation, in comparisons of line length and tone loudness, the first stimulus had the greater weight in determining the subjective difference for short ISIs, the second for longer ISIs. In comparisons of duration (auditory and visual), the second stimulus had the greater weight. For simultaneously presented line lengths, the left stimulus had the greater weight.

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.

Attention and estimated line length

Whether attention affects the estimated length of a line has been debated for a long time. Some authors have found estimated length to increase with attention; others have found that it decreased. The present study further investigated this problem with two experiments. The first confirmed that estimated length decreased with attention; however, this result had low reliability. The second experiment indicated that estimated length significantly decreased with attention for some participants and significantly increased for others. This finding accounts for the low reliability of the first experiment and for the conflicting results of previous studies. Implications of opposite effects of attention for models of sensory intensity are discussed. An interpretation of these effects in terms of response preferences is proposed.