scholarly journals A note on the equality judgment experiment in Itthipuripat, et al. (2019)

2020 ◽  
Author(s):  
Keith Allan Schneider
Keyword(s):  
Opposite Direction ◽  
Potential Effect ◽  
Decision Criteria ◽  
Low Contrast ◽  
Equality Judgment ◽  
Response Biases ◽  
Contrast Response ◽  
Judgment Data ◽  
Rule Out

Itthipuripat, Chang, Bong, & Serences (2019) investigated the effects of attention on appearance and decision criteria. Using a series of comparative and equality judgment tasks, they determined that most of the effects of attention could be explained as changes in decision criteria; however, their equality judgment experiment did reveal an effect of attention on appearance at low contrasts. Because their analysis reported Cmax, the contrast at which the equality judgement is maximum, and because Cmax is not independent of potential low-contrast response biases, I decided to reanalyze their equality judgment data. Based on this reanalysis, I was not able to rule out a potential effect of attention on appearance at low contrast. But, due to the small number and asymmetric range of contrasts probed, their experiment was not well designed to test this contrast regime, and I am not confident about their result. For the higher contrasts they tested, the measured effects of attention trended in the opposite direction.

scholarly journals Pre-print #3

2018 ◽  
Author(s):  
D. Samuel Schwarzkopf ◽  
Nonie J Finlayson ◽  
Benjamin de Haas
Keyword(s):  
Response Bias ◽  
Forced Choice ◽  
Perceptual Bias ◽  
Confounding Factors ◽  
Decision Criteria ◽  
Response Modality ◽  
Multiple Alternative ◽  
The Mean ◽  
Response Biases ◽  
Perceptual Factors

Perceptual bias is inherent to all our senses, particularly in the form of visual illusionsand aftereffects. However, many experiments measuring perceptual biases may besusceptible to non-perceptual factors, such as response bias and decision criteria. Here wequantify how robust Multiple Alternative Perceptual Search (MAPS) is for disentanglingestimates of perceptual biases from these confounding factors. First our results show thatwhile there are considerable response biases in our four-alternative forced choice design,these are unrelated to perceptual biases estimates, and these response biases are notproduced by the response modality (keyboard versus mouse). We also show that perceptualbias estimates are reduced when feedback is given on each trial, likely due to feedbackenabling observers to partially (and actively) correct for perceptual biases. However, thisdoes not impact the reliability with which MAPS detects the presence of perceptual biases.Finally, our results show that MAPS can detect actual perceptual biases and is not adecisional bias towards choosing the target in the middle of the candidate stimulusdistribution. In summary, researchers conducting a MAPS experiment should use a constantreference stimulus, but consider varying the mean of the candidate distribution. Ideally,they should not employ trial-wise feedback if the magnitude of perceptual biases is ofinterest.

scholarly journals Contrast Sensitivity Is Enhanced by Expansive Nonlinear Processing in the Lateral Geniculate Nucleus

2008 ◽  
Vol 99 (1) ◽  
pp. 367-372 ◽  
Author(s):  
Thang Duong ◽  
Ralph D. Freeman
Keyword(s):  
Visual Cortex ◽  
Lateral Geniculate Nucleus ◽  
Visual Processing ◽  
Linear Prediction ◽  
Visual Pathway ◽  
Low Contrast ◽  
Response Data ◽  
Lateral Geniculate ◽  
Nonlinear Processing ◽  
Contrast Response

The firing rates of neurons in the central visual pathway vary with stimulus strength, but not necessarily in a linear manner. In the contrast domain, the neural response function for cells in the primary visual cortex is characterized by expansive and compressive nonlinearities at low and high contrasts, respectively. A compressive nonlinearity at high contrast is also found for early visual pathway neurons in the lateral geniculate nucleus (LGN). This mechanism affects processing in the visual cortex. A fundamentally related issue is the possibility of an expansive nonlinearity at low contrast in LGN. To examine this possibility, we have obtained contrast–response data for a population of LGN neurons. We find for most cells that the best-fit function requires an expansive component. Additionally, we have measured the responses of LGN neurons to m-sequence white noise and examined the static relationship between a linear prediction and actual spike rate. We find that this static relationship is well fit by an expansive nonlinear power law with average exponent of 1.58. These results demonstrate that neurons in early visual pathways exhibit expansive nonlinear responses at low contrasts. Although this thalamic expansive nonlinearity has been largely ignored in models of early visual processing, it may have important consequences because it potentially affects the interpretation of a variety of visual functions.

Dynamic shifts of the contrast-response function

1997 ◽  
Vol 14 (3) ◽  
pp. 577-587 ◽  
Author(s):  
Jonathan D. Victor ◽  
Mary M. Conte ◽  
Keith P. Purpura
Keyword(s):  
Gain Control ◽  
Human Vision ◽  
High Contrast ◽  
Contrast Level ◽  
Low Contrast ◽  
Contrast Gain ◽  
Contrast Response Function ◽  
Stimuli Response ◽  
Response Phase ◽  
Contrast Response

AbstractWe recorded visual evoked potentials in response to square-wave contrast-reversal checkerboards undergoing a transition in the mean contrast level. Checkerboards were modulated at 4.22 Hz (8.45-Hz reversal rate). After each set of 16 cycles of reversals, stimulus contrast abruptly switched between a “high” contrast level (0.06 to 1.0) to a “low” contrast level (0.03 to 0.5). Higher contrasts attenuated responses to lower contrasts by up to a factor of 2 during the period immediately following the contrast change. Contrast-response functions derived from the initial second following a conditioning contrast shifted by a factor of 2–4 along the contrast axis. For low-contrast stimuli, response phase was an advancing function of the contrast level in the immediately preceding second. For high-contrast stimuli, response phase was independent of the prior contrast history. Steady stimulation for periods as long as 1 min produced only minor effects on response amplitude, and no detectable effects on response phase. These observations delineate the dynamics of a contrast gain control in human vision.

scholarly journals Contrast response functions in the visual wulst of the alert burrowing owl: a single-unit study

2016 ◽  
Vol 116 (4) ◽  
pp. 1765-1784 ◽  
Author(s):  
Pedro Gabrielle Vieira ◽  
João Paulo Machado de Sousa ◽  
Jerome Baron
Keyword(s):  
Single Unit ◽  
Goodness Of Fit ◽  
Dynamic Range ◽  
Information Criterion ◽  
Future Research ◽  
Response Functions ◽  
Athene Cunicularia ◽  
Low Contrast ◽  
Burrowing Owl ◽  
Contrast Response

The neuronal representation of luminance contrast has not been thoroughly studied in birds. Here we present a detailed quantitative analysis of the contrast response of 120 individual neurons recorded from the visual wulst of awake burrowing owls ( Athene cunicularia). Stimuli were sine-wave gratings presented within the cell classical receptive field and optimized in terms of eye preference, direction of drift, and spatiotemporal frequency. As contrast intensity was increased from zero to near 100%, most cells exhibited a monotonic response profile with a compressive, at times saturating, nonlinearity at higher contrasts. However, contrast response functions were found to have a highly variable shape across cells. With the view to capture a systematic trend in the data, we assessed the performance of four plausible models (linear, power, logarithmic, and hyperbolic ratio) using classical goodness-of-fit measures and more rigorous statistical tools for multimodel inferences based on the Akaike information criterion. From this analysis, we conclude that a high degree of model uncertainty is present in our data, meaning that no single descriptor is able on its own to capture the heterogeneous nature of single-unit contrast responses in the wulst. We further show that the generalizability of the hyperbolic ratio model established, for example, in the primary visual cortex of cats and monkeys is not tenable in the owl wulst mainly because most neurons in this area have a much wider dynamic range that starts at low contrast. The challenge for future research will be to understand the functional implications of these findings.

Controlling for Response Order Effects in Ranking Items Using Latent Choice Factor Modeling

2015 ◽  
Vol 46 (2) ◽  
pp. 218-241 ◽  
Author(s):  
Ingrid Vriens ◽  
Guy Moors ◽  
John Gelissen ◽  
Jeroen K. Vermunt
Keyword(s):  
Work Values ◽  
Standard Procedure ◽  
Order Effect ◽  
Primacy Effect ◽  
Order Effects ◽  
Sociological Research ◽  
Ranking Data ◽  
Factor Modeling ◽  
Response Biases ◽  
Rule Out

Measuring values in sociological research sometimes involves the use of ranking data. A disadvantage of a ranking assignment is that the order in which the items are presented might influence the choice preferences of respondents regardless of the content being measured. The standard procedure to rule out such effects is to randomize the order of items across respondents. However, implementing this design may be impractical and the biasing impact of a response order effect cannot be evaluated. We use a latent choice factor (LCF) model that allows statistically controlling for response order effects. Furthermore, the model adequately deals with the known issue of ipsativity of ranking data. Applying this model to a Dutch survey on work values, we show that a primacy effect accounts for response order bias in item preferences. Our findings demonstrate the usefulness of the LCF model in modeling ranking data while taking into account particular response biases.

Visual evoked potentials and magnocellular and parvocellular segregation

2000 ◽  
Vol 17 (4) ◽  
pp. 579-590 ◽  
Author(s):  
INGER RUDVIN ◽  
ARNE VALBERG ◽  
BJØRG ELISABETH KILAVIK
Keyword(s):  
Evoked Potentials ◽  
Visual Evoked Potentials ◽  
Single Cells ◽  
High Gain ◽  
High Contrast ◽  
Low Contrast ◽  
Contrast Gain ◽  
Time To Peak ◽  
Contrast Response ◽  
Visual Evoked

We have measured visual evoked potentials (VEPs) to luminance-modulated, square-wave alternating, 3-deg homogeneous disks for stimulus frequencies ranging from 1 Hz to 16.7 Hz. The aim of the study was to determine the range of frequencies at which we could reproduce the two-branched contrast-response (C-R) curves we had seen at 1 Hz (Valberg & Rudvin, 1997) and which we interpreted as magnocellular (MC) and parvocellular (PC) segregation. Low-contrast stimuli elicited relatively simple responses to luminance increments resulting in waveforms that may be the signatures of inputs from magnocellular channels to the visual cortex. At all frequencies, the C-R curves of the main waveforms were characterized by a steep slope at low contrasts and a leveling off at 10%–20% Michelson contrast. This was typically followed by an abrupt increase in slope at higher contrasts, giving a distinctive two-branched C-R curve. On the assumption that the low-contrast, high-gain branch reflects the responsivity of magnocellular-pathway inputs to the cortex, the high-contrast branch may be attributed to additional parvocellular activation. While a two-branched curve was maintained for frequencies up to 8 Hz, the high-contrast response was significantly compromised at 16.7 Hz, revealing a differential low-pass filtering. A model decomposing the measured VEP response into two separate C-R curves yielded a difference in sensitivity of the putative MC- and PC-mediated response that, when plotted as a function of frequency, followed a trend similar to that found for single cells. Due to temporal overlap of responses, the MC and PC contributions to the waveforms were hard to distinguish in the transient VEP. However, curves of time-to-peak (delay) as a function of contrast often went through a minimum before the high-contrast gain increase of the corresponding C-R curve, supporting the notion of a recruitment of new cell ensembles in the transition from low to high contrasts.

Contrast Dependence of Contextual Effects in Macaque Striate Cortex

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 95-95
Author(s):  
J B Levitt ◽  
J S Lund
Keyword(s):  
Striate Cortex ◽  
Receptive Fields ◽  
Contextual Effects ◽  
High Contrast ◽  
Neuronal Responses ◽  
Low Contrast ◽  
Response Versus ◽  
Direction Tuning ◽  
Contrast Response ◽  
Lower Slope

We have studied the effect of varying stimulus contrast on the modulatory effects exerted on V1 receptive fields by surrounding portions of the visual field. We used standard extracellular techniques to record unit activity in striate cortex of paralysed, opiate-anaesthetised macaque monkeys. We measured the orientation and direction tuning of neurons at several contrasts, with and without the presence of a surrounding stimulus that itself evoked minimal responses from the neuron. At both high and low stimulus contrasts, surround stimuli modulated responses to centre stimuli when the orientation and direction of the centre and surround were in the appropriate (though not necessarily matched) relationship. At low contrasts, we observed more profound suppression and facilitation. However, this did not simply reflect release from response saturation. At low contrasts, a greater range of surround orientations could modulate neuronal responses. This sometimes resulted in identical surround stimuli being suppressive when pairs with high-contrast centre stimuli, but facilitative when paired with low-contrast centre stimuli. Further evidence against response saturation at high contrasts was the frequent anisotropy in the suppression, ie suppression was direction-selective at high contrast, but nondirectional at low contrasts. Such contrast-dependent effects were also revealed by measurements of contrast response functions in the presence of the surround. We sometimes observed not only a decrease in the response to high-contrast stimuli and a lower slope of the response-versus-contrast curve but also an increase in responsiveness to low-contrast centre stimuli in the presence of nominally suppressive surround stimuli. Contextual effects in striate cortex thus depend importantly on the relative contrasts of centre and surround stimuli.

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