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Memory bias in the temporal bisection point.

Levy JM, Namboodiri VM, Hussain Shuler MG - Front Integr Neurosci (2015)

Bottom Line: The ability to time intervals confers organisms, including humans, with many remarkable capabilities.Finally, by using two sets of referent durations, we showed that only memory bias-corrected measures were consistent with a previously reported effect in which the ratio of the referents affects the location of the bisection point.These results suggest that memory effects should be considered in temporal tasks.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, Johns Hopkins University Baltimore, MD, USA.

ABSTRACT
The ability to time intervals confers organisms, including humans, with many remarkable capabilities. A common method for studying interval timing is classification, in which a subject must indicate whether a given probe duration is nearer a previously learned short or long reference interval. This task is designed to reveal the probe duration that is equally likely to be labeled as short or long, known as the temporal bisection point. Studies have found that this bisection point is influenced by a variety of factors including the ratio of the target intervals, the spacing of the probe durations, the modalities of the stimuli, the attentional load, and the inter-trial duration. While several of these factors are thought to be mediated by memory effects, the prototypical classification task affords no opportunity to measure these memory effects directly. Here, we present a novel bisection task, termed the "Bisection by Classification and Production" (BiCaP) task, in which classification trials are interleaved with trials in which subjects must produce either the short or long referents or their midpoint. Using this method, we found a significant correlation between the means of the remembered referents and the bisection points for both classification and production trials. We then cross-validated the bisection points for production and classification trials by showing that they were not statistically differentiable. In addition to these population-level effects, we found within-subject evidence for co-variation across a session between the production bisection points and the means of the remembered referents. Finally, by using two sets of referent durations, we showed that only memory bias-corrected measures were consistent with a previously reported effect in which the ratio of the referents affects the location of the bisection point. These results suggest that memory effects should be considered in temporal tasks.

No MeSH data available.


Related in: MedlinePlus

Performance on the BiCaP Task. (A) Design of the BiCaP task which consists of two trial types—classification and production—pseudo-randomly interleaved. (B) The proportion that a given probe duration is classified long (left panel, black dots with SEMs across subjects) for the population in the 1/5 s referent group. Mean produced intervals for the short reference (black dotted line), long reference (black dotted line), and midpoint (red dotted line) are shown along with the SEM (gray bars). The bias-corrected arithmetic mean (AM; i.e., the AM of the produced short and long referent intervals) is shown in green. Note that both the produced midpoint and the bias-corrected AM lie above the true AM of the 1/5 s reference intervals (i.e., 3 s). The mean coefficient of variation (CV) across subjects for each production interval is shown with SEMs on the middle panel. The empirical cumulative distribution function (CDF) of production times for the short reference (blue), long reference (red), and midpoint (yellow) is shown on the right panel. (C) The population data for the 2/4 s group.
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Figure 1: Performance on the BiCaP Task. (A) Design of the BiCaP task which consists of two trial types—classification and production—pseudo-randomly interleaved. (B) The proportion that a given probe duration is classified long (left panel, black dots with SEMs across subjects) for the population in the 1/5 s referent group. Mean produced intervals for the short reference (black dotted line), long reference (black dotted line), and midpoint (red dotted line) are shown along with the SEM (gray bars). The bias-corrected arithmetic mean (AM; i.e., the AM of the produced short and long referent intervals) is shown in green. Note that both the produced midpoint and the bias-corrected AM lie above the true AM of the 1/5 s reference intervals (i.e., 3 s). The mean coefficient of variation (CV) across subjects for each production interval is shown with SEMs on the middle panel. The empirical cumulative distribution function (CDF) of production times for the short reference (blue), long reference (red), and midpoint (yellow) is shown on the right panel. (C) The population data for the 2/4 s group.

Mentions: To assess the effects of memory on the bisection point, we developed the “Bisection by Classification and Production” (BiCaP) task (Figure 1A), which consists of classification (top) and production (bottom) trials. Using this design, we were able to compare the bisection point produced from classification trials with the midpoint from production trials and, simultaneously, assess what the subjects believe the reference intervals to be. We used two sets of reference intervals, 1/5 and 2/4 s, for different cohorts.


Memory bias in the temporal bisection point.

Levy JM, Namboodiri VM, Hussain Shuler MG - Front Integr Neurosci (2015)

Performance on the BiCaP Task. (A) Design of the BiCaP task which consists of two trial types—classification and production—pseudo-randomly interleaved. (B) The proportion that a given probe duration is classified long (left panel, black dots with SEMs across subjects) for the population in the 1/5 s referent group. Mean produced intervals for the short reference (black dotted line), long reference (black dotted line), and midpoint (red dotted line) are shown along with the SEM (gray bars). The bias-corrected arithmetic mean (AM; i.e., the AM of the produced short and long referent intervals) is shown in green. Note that both the produced midpoint and the bias-corrected AM lie above the true AM of the 1/5 s reference intervals (i.e., 3 s). The mean coefficient of variation (CV) across subjects for each production interval is shown with SEMs on the middle panel. The empirical cumulative distribution function (CDF) of production times for the short reference (blue), long reference (red), and midpoint (yellow) is shown on the right panel. (C) The population data for the 2/4 s group.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4493391&req=5

Figure 1: Performance on the BiCaP Task. (A) Design of the BiCaP task which consists of two trial types—classification and production—pseudo-randomly interleaved. (B) The proportion that a given probe duration is classified long (left panel, black dots with SEMs across subjects) for the population in the 1/5 s referent group. Mean produced intervals for the short reference (black dotted line), long reference (black dotted line), and midpoint (red dotted line) are shown along with the SEM (gray bars). The bias-corrected arithmetic mean (AM; i.e., the AM of the produced short and long referent intervals) is shown in green. Note that both the produced midpoint and the bias-corrected AM lie above the true AM of the 1/5 s reference intervals (i.e., 3 s). The mean coefficient of variation (CV) across subjects for each production interval is shown with SEMs on the middle panel. The empirical cumulative distribution function (CDF) of production times for the short reference (blue), long reference (red), and midpoint (yellow) is shown on the right panel. (C) The population data for the 2/4 s group.
Mentions: To assess the effects of memory on the bisection point, we developed the “Bisection by Classification and Production” (BiCaP) task (Figure 1A), which consists of classification (top) and production (bottom) trials. Using this design, we were able to compare the bisection point produced from classification trials with the midpoint from production trials and, simultaneously, assess what the subjects believe the reference intervals to be. We used two sets of reference intervals, 1/5 and 2/4 s, for different cohorts.

Bottom Line: The ability to time intervals confers organisms, including humans, with many remarkable capabilities.Finally, by using two sets of referent durations, we showed that only memory bias-corrected measures were consistent with a previously reported effect in which the ratio of the referents affects the location of the bisection point.These results suggest that memory effects should be considered in temporal tasks.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, Johns Hopkins University Baltimore, MD, USA.

ABSTRACT
The ability to time intervals confers organisms, including humans, with many remarkable capabilities. A common method for studying interval timing is classification, in which a subject must indicate whether a given probe duration is nearer a previously learned short or long reference interval. This task is designed to reveal the probe duration that is equally likely to be labeled as short or long, known as the temporal bisection point. Studies have found that this bisection point is influenced by a variety of factors including the ratio of the target intervals, the spacing of the probe durations, the modalities of the stimuli, the attentional load, and the inter-trial duration. While several of these factors are thought to be mediated by memory effects, the prototypical classification task affords no opportunity to measure these memory effects directly. Here, we present a novel bisection task, termed the "Bisection by Classification and Production" (BiCaP) task, in which classification trials are interleaved with trials in which subjects must produce either the short or long referents or their midpoint. Using this method, we found a significant correlation between the means of the remembered referents and the bisection points for both classification and production trials. We then cross-validated the bisection points for production and classification trials by showing that they were not statistically differentiable. In addition to these population-level effects, we found within-subject evidence for co-variation across a session between the production bisection points and the means of the remembered referents. Finally, by using two sets of referent durations, we showed that only memory bias-corrected measures were consistent with a previously reported effect in which the ratio of the referents affects the location of the bisection point. These results suggest that memory effects should be considered in temporal tasks.

No MeSH data available.


Related in: MedlinePlus