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Contradictory behavioral biases result from the influence of past stimuli on perception.

Raviv O, Lieder I, Loewenstein Y, Ahissar M - PLoS Comput. Biol. (2014)

Bottom Line: Here we consider human performance in the 2AFC tone frequency discrimination task, utilizing two standard protocols.Namely, participants perform better when the reference is in a specific interval.The success of this account implies that even simple discriminations reflect a combination of sensory limitations, memory limitations, and the ability to utilize stimuli statistics.

View Article: PubMed Central - PubMed

Affiliation: The Edmond & Lily Safra Center for Brain Sciences, Interdisciplinary Center for Neural Computation, Hebrew University, Jerusalem, Israel.

ABSTRACT
Biases such as the preference of a particular response for no obvious reason, are an integral part of psychophysics. Such biases have been reported in the common two-alternative forced choice (2AFC) experiments, where participants are instructed to compare two consecutively presented stimuli. However, the principles underlying these biases are largely unknown and previous studies have typically used ad-hoc explanations to account for them. Here we consider human performance in the 2AFC tone frequency discrimination task, utilizing two standard protocols. In both protocols, each trial contains a reference stimulus. In one (Reference-Lower protocol), the frequency of the reference stimulus is always lower than that of the comparison stimulus, whereas in the other (Reference protocol), the frequency of the reference stimulus is either lower or higher than that of the comparison stimulus. We find substantial interval biases. Namely, participants perform better when the reference is in a specific interval. Surprisingly, the biases in the two experiments are opposite: performance is better when the reference is in the first interval in the Reference protocol, but is better when the reference is second in the Reference-Lower protocol. This inconsistency refutes previous accounts of the interval bias, and is resolved when experiments statistics is considered. Viewing perception as incorporation of sensory input with prior knowledge accumulated during the experiment accounts for the seemingly contradictory biases both qualitatively and quantitatively. The success of this account implies that even simple discriminations reflect a combination of sensory limitations, memory limitations, and the ability to utilize stimuli statistics.

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Performance in trials in which first tone is higher than the second () and trials in which the second tone is higher than the first () in Reference-Lower protocol (A), and Reference protocol (B).Error bars represent the SEM across the participants. The insets above each bar represent the trial types that constitute that bar using the same notation as in Fig. 1. In Reference-Lower protocol performance is significantly better in  trials, while in Reference protocol it is better in  trials.
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pcbi-1003948-g003: Performance in trials in which first tone is higher than the second () and trials in which the second tone is higher than the first () in Reference-Lower protocol (A), and Reference protocol (B).Error bars represent the SEM across the participants. The insets above each bar represent the trial types that constitute that bar using the same notation as in Fig. 1. In Reference-Lower protocol performance is significantly better in trials, while in Reference protocol it is better in trials.

Mentions: An alternative account for the differences in performance in the Reference-Lower protocol (Fig. 2A) could have been a bias in favour of responding that the frequency of the first interval is higher (i.e., responding ""). The reason is that in the Reference-Lower protocol, Ref2 trials are those in which the correct response is that the frequency of the first tone is higher. If such a bias existed in the Reference protocol, more “” responses should be observed. This is not the case: participants responded "" in 49.2%±0.6% (mean ± SEM across participants) of the trials. To further test whether a response bias exists in the Reference protocol, we separated the trials according to which of the two tones was higher, the first or the second (i.e., the correct response). In the Reference-Lower protocol, this division is equivalent to the division according to the position of the reference (hence Fig. 3A is a re-plot of Fig. 2A). However, in the Reference protocol, the division of the trials according to which stimulus was higher is uncorrelated with the division according to the position of the reference. In contrast to the hypothesis of response bias, participants did not perform better when the first tone was higher. Rather, there was a small, yet significant tendency in the opposite direction: participants responded correctly in 79.4%±0.7% when the first tone was higher, compared to 81.5%±0.6% when the second tone was higher (, paired t-test; , , Fig. 3). This result indicates that a response bias, i.e. participants' tendency to respond "", is not a consistent account of the bias.


Contradictory behavioral biases result from the influence of past stimuli on perception.

Raviv O, Lieder I, Loewenstein Y, Ahissar M - PLoS Comput. Biol. (2014)

Performance in trials in which first tone is higher than the second () and trials in which the second tone is higher than the first () in Reference-Lower protocol (A), and Reference protocol (B).Error bars represent the SEM across the participants. The insets above each bar represent the trial types that constitute that bar using the same notation as in Fig. 1. In Reference-Lower protocol performance is significantly better in  trials, while in Reference protocol it is better in  trials.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4256013&req=5

pcbi-1003948-g003: Performance in trials in which first tone is higher than the second () and trials in which the second tone is higher than the first () in Reference-Lower protocol (A), and Reference protocol (B).Error bars represent the SEM across the participants. The insets above each bar represent the trial types that constitute that bar using the same notation as in Fig. 1. In Reference-Lower protocol performance is significantly better in trials, while in Reference protocol it is better in trials.
Mentions: An alternative account for the differences in performance in the Reference-Lower protocol (Fig. 2A) could have been a bias in favour of responding that the frequency of the first interval is higher (i.e., responding ""). The reason is that in the Reference-Lower protocol, Ref2 trials are those in which the correct response is that the frequency of the first tone is higher. If such a bias existed in the Reference protocol, more “” responses should be observed. This is not the case: participants responded "" in 49.2%±0.6% (mean ± SEM across participants) of the trials. To further test whether a response bias exists in the Reference protocol, we separated the trials according to which of the two tones was higher, the first or the second (i.e., the correct response). In the Reference-Lower protocol, this division is equivalent to the division according to the position of the reference (hence Fig. 3A is a re-plot of Fig. 2A). However, in the Reference protocol, the division of the trials according to which stimulus was higher is uncorrelated with the division according to the position of the reference. In contrast to the hypothesis of response bias, participants did not perform better when the first tone was higher. Rather, there was a small, yet significant tendency in the opposite direction: participants responded correctly in 79.4%±0.7% when the first tone was higher, compared to 81.5%±0.6% when the second tone was higher (, paired t-test; , , Fig. 3). This result indicates that a response bias, i.e. participants' tendency to respond "", is not a consistent account of the bias.

Bottom Line: Here we consider human performance in the 2AFC tone frequency discrimination task, utilizing two standard protocols.Namely, participants perform better when the reference is in a specific interval.The success of this account implies that even simple discriminations reflect a combination of sensory limitations, memory limitations, and the ability to utilize stimuli statistics.

View Article: PubMed Central - PubMed

Affiliation: The Edmond & Lily Safra Center for Brain Sciences, Interdisciplinary Center for Neural Computation, Hebrew University, Jerusalem, Israel.

ABSTRACT
Biases such as the preference of a particular response for no obvious reason, are an integral part of psychophysics. Such biases have been reported in the common two-alternative forced choice (2AFC) experiments, where participants are instructed to compare two consecutively presented stimuli. However, the principles underlying these biases are largely unknown and previous studies have typically used ad-hoc explanations to account for them. Here we consider human performance in the 2AFC tone frequency discrimination task, utilizing two standard protocols. In both protocols, each trial contains a reference stimulus. In one (Reference-Lower protocol), the frequency of the reference stimulus is always lower than that of the comparison stimulus, whereas in the other (Reference protocol), the frequency of the reference stimulus is either lower or higher than that of the comparison stimulus. We find substantial interval biases. Namely, participants perform better when the reference is in a specific interval. Surprisingly, the biases in the two experiments are opposite: performance is better when the reference is in the first interval in the Reference protocol, but is better when the reference is second in the Reference-Lower protocol. This inconsistency refutes previous accounts of the interval bias, and is resolved when experiments statistics is considered. Viewing perception as incorporation of sensory input with prior knowledge accumulated during the experiment accounts for the seemingly contradictory biases both qualitatively and quantitatively. The success of this account implies that even simple discriminations reflect a combination of sensory limitations, memory limitations, and the ability to utilize stimuli statistics.

Show MeSH