Limits...
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.

Show MeSH
Comparison of model simulations (white) to experimental data (blue).A–B: Performance in trials in which the reference is first (Ref1) and trials in which the reference is second (Ref2) in Reference-Lower protocol (A) and Reference protocol (B). C–D: Performance in trials in which second tone is higher than the first () and trials in which the first tone is higher than the second () in Reference-Lower protocol (C), and Reference protocol (D). Note that panel C presents the same data as panel A, due to the equivalence of the Ref1 vs Ref2 and  vs.  divisions of the trials in the Reference-Lower protocol. Error bars represent the SEM across the participants. p-values are for paired t-tests, uncorrected for multiple comparisons.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4256013&req=5

pcbi-1003948-g006: Comparison of model simulations (white) to experimental data (blue).A–B: Performance in trials in which the reference is first (Ref1) and trials in which the reference is second (Ref2) in Reference-Lower protocol (A) and Reference protocol (B). C–D: Performance in trials in which second tone is higher than the first () and trials in which the first tone is higher than the second () in Reference-Lower protocol (C), and Reference protocol (D). Note that panel C presents the same data as panel A, due to the equivalence of the Ref1 vs Ref2 and vs. divisions of the trials in the Reference-Lower protocol. Error bars represent the SEM across the participants. p-values are for paired t-tests, uncorrected for multiple comparisons.

Mentions: Where are the parameters estimated in [15], as explained above. The parameter σ represents the observer's noise; for each participant, we fitted the model parameter σ and simulated the model in the two protocols (for the values of and the details of the fitting, see Methods). Fig. 6 compares the performance of the simulated participants (white) to that of the participants (blue) as a function of the protocol (Reference Lower, A, C; Reference, B, D), divided according to the position of the reference (A,B, experimental data copied from Fig. 2), and the position of the higher tone (C, D, experimental data copied from Fig. 3). Overall, the behavior of the simulated participants was remarkably similar to that of the human participants. To quantify the quality of the fit of the memory trace model to the data, we compared it to a naive model that assumes no history effect:(3)


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

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

Comparison of model simulations (white) to experimental data (blue).A–B: Performance in trials in which the reference is first (Ref1) and trials in which the reference is second (Ref2) in Reference-Lower protocol (A) and Reference protocol (B). C–D: Performance in trials in which second tone is higher than the first () and trials in which the first tone is higher than the second () in Reference-Lower protocol (C), and Reference protocol (D). Note that panel C presents the same data as panel A, due to the equivalence of the Ref1 vs Ref2 and  vs.  divisions of the trials in the Reference-Lower protocol. Error bars represent the SEM across the participants. p-values are for paired t-tests, uncorrected for multiple comparisons.
© Copyright Policy
Related In: Results  -  Collection

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

pcbi-1003948-g006: Comparison of model simulations (white) to experimental data (blue).A–B: Performance in trials in which the reference is first (Ref1) and trials in which the reference is second (Ref2) in Reference-Lower protocol (A) and Reference protocol (B). C–D: Performance in trials in which second tone is higher than the first () and trials in which the first tone is higher than the second () in Reference-Lower protocol (C), and Reference protocol (D). Note that panel C presents the same data as panel A, due to the equivalence of the Ref1 vs Ref2 and vs. divisions of the trials in the Reference-Lower protocol. Error bars represent the SEM across the participants. p-values are for paired t-tests, uncorrected for multiple comparisons.
Mentions: Where are the parameters estimated in [15], as explained above. The parameter σ represents the observer's noise; for each participant, we fitted the model parameter σ and simulated the model in the two protocols (for the values of and the details of the fitting, see Methods). Fig. 6 compares the performance of the simulated participants (white) to that of the participants (blue) as a function of the protocol (Reference Lower, A, C; Reference, B, D), divided according to the position of the reference (A,B, experimental data copied from Fig. 2), and the position of the higher tone (C, D, experimental data copied from Fig. 3). Overall, the behavior of the simulated participants was remarkably similar to that of the human participants. To quantify the quality of the fit of the memory trace model to the data, we compared it to a naive model that assumes no history effect:(3)

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