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Hysteresis as an implicit prior in tactile spatial decision making.

Thiel SD, Bitzer S, Nierhaus T, Kalberlah C, Preusser S, Neumann J, Nikulin VV, van der Meer E, Villringer A, Pleger B - PLoS ONE (2014)

Bottom Line: We applied a variant of the classical 2-point discrimination task and found that hysteresis influenced perceptual decision making: Participants were more likely to decide 'same' rather than 'different' on successively presented pin distances.In a direct comparison between the influence of applied pin distances (explicit stimulus property) and hysteresis, we found that on average, stimulus property explained significantly more variance of participants' decisions than hysteresis.However, when focusing on pin distances at threshold, we found a trend for hysteresis to explain more variance.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany ; Department of Psychology, Faculty of Mathematics and Natural Sciences II, Humboldt-University, Berlin, Germany.

ABSTRACT
Perceptual decisions not only depend on the incoming information from sensory systems but constitute a combination of current sensory evidence and internally accumulated information from past encounters. Although recent evidence emphasizes the fundamental role of prior knowledge for perceptual decision making, only few studies have quantified the relevance of such priors on perceptual decisions and examined their interplay with other decision-relevant factors, such as the stimulus properties. In the present study we asked whether hysteresis, describing the stability of a percept despite a change in stimulus property and known to occur at perceptual thresholds, also acts as a form of an implicit prior in tactile spatial decision making, supporting the stability of a decision across successively presented random stimuli (i.e., decision hysteresis). We applied a variant of the classical 2-point discrimination task and found that hysteresis influenced perceptual decision making: Participants were more likely to decide 'same' rather than 'different' on successively presented pin distances. In a direct comparison between the influence of applied pin distances (explicit stimulus property) and hysteresis, we found that on average, stimulus property explained significantly more variance of participants' decisions than hysteresis. However, when focusing on pin distances at threshold, we found a trend for hysteresis to explain more variance. Furthermore, the less variance was explained by the pin distance on a given decision, the more variance was explained by hysteresis, and vice versa. Our findings suggest that hysteresis acts as an implicit prior in tactile spatial decision making that becomes increasingly important when explicit stimulus properties provide decreasing evidence.

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Individual psychometric functions of the 2-point discrimination task.The figure shows individual psychometric functions for each of the 26 participants. The percentages of ‘distance felt’ answers across pin distances (depicted as dots) were fitted with a binary logistic regression and the spatial discrimination threshold was defined as the pin distance closest to the 50% crossing of the fitted sigmoid curve. Error bars are confidence limits derived from bootstrapping 1999 curve fitting simulations. Subjects 3, 4, 11, 13, 14, 15, and 21 were excluded from further analyses (see Materials and Methods).
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pone-0089802-g001: Individual psychometric functions of the 2-point discrimination task.The figure shows individual psychometric functions for each of the 26 participants. The percentages of ‘distance felt’ answers across pin distances (depicted as dots) were fitted with a binary logistic regression and the spatial discrimination threshold was defined as the pin distance closest to the 50% crossing of the fitted sigmoid curve. Error bars are confidence limits derived from bootstrapping 1999 curve fitting simulations. Subjects 3, 4, 11, 13, 14, 15, and 21 were excluded from further analyses (see Materials and Methods).

Mentions: We calculated psychometric functions using the psignifit toolbox version 2.5.6 for Matlab (see http://bootstrap-software.org/psignifit/) offering the maximum-likelihood method by Wichmann and Hill [26]. The percentages of ‘distance felt’ answers across increasing pin distances were fitted using a binary logistic regression (see e.g., [27]–[29]). The spatial discrimination threshold was defined as the pin distance closest to the 50% crossing of the fitted sigmoid curve. First, we estimated the discrimination threshold for each participant and each of the five sessions to assess stability of discrimination thresholds. Then, we estimated the discrimination threshold of the fitted binary logistic regression for pooled sessions which we used for further analyses (see Figure 1 for individual psychometric functions). Subsequent analyses were carried out for pin distances grouped according to the individual discrimination threshold (pin distance group ‘threshold’), the next two larger (‘threshold+1’, ‘threshold+2’) and the next two smaller pin distances (‘threshold−1’, ‘threshold−2’). We only included participants whose discrimination performance covered the full range of the applied pin distances (i.e., not more than 30% of ‘distance felt’ answers for the smallest distance 0.7 mm and more than 70% ‘distance felt’ answers for the largest pin distance 2.5 mm, respectively). Accordingly, data from seven participants were excluded and group analyses were based on the remaining 19 participants (see Figure 1 for psychometric functions of subjects which were excluded and included). As the maximum trial length was set to 2400 ms, trials with reaction times slower than 2400 ms were discarded from group analyses (out of 2170 trials from 19 participants, 109 trials in 9 participants were discarded).


Hysteresis as an implicit prior in tactile spatial decision making.

Thiel SD, Bitzer S, Nierhaus T, Kalberlah C, Preusser S, Neumann J, Nikulin VV, van der Meer E, Villringer A, Pleger B - PLoS ONE (2014)

Individual psychometric functions of the 2-point discrimination task.The figure shows individual psychometric functions for each of the 26 participants. The percentages of ‘distance felt’ answers across pin distances (depicted as dots) were fitted with a binary logistic regression and the spatial discrimination threshold was defined as the pin distance closest to the 50% crossing of the fitted sigmoid curve. Error bars are confidence limits derived from bootstrapping 1999 curve fitting simulations. Subjects 3, 4, 11, 13, 14, 15, and 21 were excluded from further analyses (see Materials and Methods).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3935932&req=5

pone-0089802-g001: Individual psychometric functions of the 2-point discrimination task.The figure shows individual psychometric functions for each of the 26 participants. The percentages of ‘distance felt’ answers across pin distances (depicted as dots) were fitted with a binary logistic regression and the spatial discrimination threshold was defined as the pin distance closest to the 50% crossing of the fitted sigmoid curve. Error bars are confidence limits derived from bootstrapping 1999 curve fitting simulations. Subjects 3, 4, 11, 13, 14, 15, and 21 were excluded from further analyses (see Materials and Methods).
Mentions: We calculated psychometric functions using the psignifit toolbox version 2.5.6 for Matlab (see http://bootstrap-software.org/psignifit/) offering the maximum-likelihood method by Wichmann and Hill [26]. The percentages of ‘distance felt’ answers across increasing pin distances were fitted using a binary logistic regression (see e.g., [27]–[29]). The spatial discrimination threshold was defined as the pin distance closest to the 50% crossing of the fitted sigmoid curve. First, we estimated the discrimination threshold for each participant and each of the five sessions to assess stability of discrimination thresholds. Then, we estimated the discrimination threshold of the fitted binary logistic regression for pooled sessions which we used for further analyses (see Figure 1 for individual psychometric functions). Subsequent analyses were carried out for pin distances grouped according to the individual discrimination threshold (pin distance group ‘threshold’), the next two larger (‘threshold+1’, ‘threshold+2’) and the next two smaller pin distances (‘threshold−1’, ‘threshold−2’). We only included participants whose discrimination performance covered the full range of the applied pin distances (i.e., not more than 30% of ‘distance felt’ answers for the smallest distance 0.7 mm and more than 70% ‘distance felt’ answers for the largest pin distance 2.5 mm, respectively). Accordingly, data from seven participants were excluded and group analyses were based on the remaining 19 participants (see Figure 1 for psychometric functions of subjects which were excluded and included). As the maximum trial length was set to 2400 ms, trials with reaction times slower than 2400 ms were discarded from group analyses (out of 2170 trials from 19 participants, 109 trials in 9 participants were discarded).

Bottom Line: We applied a variant of the classical 2-point discrimination task and found that hysteresis influenced perceptual decision making: Participants were more likely to decide 'same' rather than 'different' on successively presented pin distances.In a direct comparison between the influence of applied pin distances (explicit stimulus property) and hysteresis, we found that on average, stimulus property explained significantly more variance of participants' decisions than hysteresis.However, when focusing on pin distances at threshold, we found a trend for hysteresis to explain more variance.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany ; Department of Psychology, Faculty of Mathematics and Natural Sciences II, Humboldt-University, Berlin, Germany.

ABSTRACT
Perceptual decisions not only depend on the incoming information from sensory systems but constitute a combination of current sensory evidence and internally accumulated information from past encounters. Although recent evidence emphasizes the fundamental role of prior knowledge for perceptual decision making, only few studies have quantified the relevance of such priors on perceptual decisions and examined their interplay with other decision-relevant factors, such as the stimulus properties. In the present study we asked whether hysteresis, describing the stability of a percept despite a change in stimulus property and known to occur at perceptual thresholds, also acts as a form of an implicit prior in tactile spatial decision making, supporting the stability of a decision across successively presented random stimuli (i.e., decision hysteresis). We applied a variant of the classical 2-point discrimination task and found that hysteresis influenced perceptual decision making: Participants were more likely to decide 'same' rather than 'different' on successively presented pin distances. In a direct comparison between the influence of applied pin distances (explicit stimulus property) and hysteresis, we found that on average, stimulus property explained significantly more variance of participants' decisions than hysteresis. However, when focusing on pin distances at threshold, we found a trend for hysteresis to explain more variance. Furthermore, the less variance was explained by the pin distance on a given decision, the more variance was explained by hysteresis, and vice versa. Our findings suggest that hysteresis acts as an implicit prior in tactile spatial decision making that becomes increasingly important when explicit stimulus properties provide decreasing evidence.

Show MeSH
Related in: MedlinePlus