تصمیم‌گیری ادراکی در حضور محرک طبیعی: یک مطالعه رفتاری

مقدمه: بررسی کمّی تاثیر اطلاعات چندگانه مکانی در تصمیم‌گیری ادراکی، به دلیل پیچیدگی کنترل این اطلاعات در محرک‌های طبیعی کمتر مورد توجه بوده ‌است. در این پژوهش با کنترل نظام‌مند تعداد و حجم اطلاعات مکانی در یک محرک طبیعی، به مقایسه کمّی وزن این اطلاعات و تاثیر آن در تفکیک چهره‌های خنثی پرداخته می‌شود. اهمیت این مسئله در مطالعه‌ کمّی یک محرک پیچیده طبیعی در بستر تصمیم‌گیری ادراکی است. روش‌ کار: آزمونی با قابلیت کنترل نظام‌مند اطلاعات چندگانه مکانی (ناحیه چشم، بینی و دهان) با ادغام تصاویر چهره طراحی و اجرا شد. این تصاویر متشکل از یک یا سه مولفه حاوی اطلاعات مکانی متغیر در زمان بودند که با ماسک ترکیب و به صورت تصادفی با سطوح سختی متفاوت نمایش داده می‌شدند. از شرکت‌کنندگان خواسته شد تا شباهت بیشتر محرک به یکی از دو نمونه چهره را به صورت پاسخ ‌آزاد اعلام کنند. یافته‌ها: دامنه مثبت کرنل‌های روان‌فیزیک برای هر مولفه، نشان می‌دهد اخذ تصمیم با جمع‌آوری اطلاعات مکانی صورت می‌گیرد. دامنه کرنل‌ برای تمام مولفه‌ها در آزمایه‌های سه ‌مولفه‌ای تفاوت معناداری از صفر دارد که حاکی از اثر تقویت‌کننده وزن اطلاعات مولفه‌ها در راهبردهای تصمیم است. جمع‌آوری اطلاعات چندگانه مکانی را می‌توان به صورت عمدتا خطی و با وزن موثر هر مولفه با مدل جمع‌آوری بی‌نقص شواهد توضیح داد.نتیجه‌گیری: سازوکار تصمیم‌گیری ادراکی در حضور محرک طبیعی با جمع‌آوری بی‌نقص اطلاعات مکانی_زمانی قابل توصیف است. این پژوهش توسعه‌ای از مطالعات پیشین در حضور محرک‌های ساده است که حاوی اطلاعات یکنواخت مکانی بوده‌اند.

Perceptual decision-making in the presence of natural stimulus: A behavioral study

IntroductionPerceptual decisionmaking studies have widely focused on simple stimuli with uniform distribution of spatial information, say Random Dot Motion to address the accumulation of sensory evidence resulting in a binary decision. However, the realworld stimuli are mostly complex containing a nonuniform distribution of spatial information. Hence perceptual decisionmaking process in the presence of natural stimuli has remained unknown, likely because of the complexity in controlling the multiple pieces of information over time to study their effect on decisions. Recently, a novel framework has been introduced to broaden perceptual decisionmaking studies into multispatial stimuli by a face discrimination task with controlled fluctuating local features (eyes, nose, and mouth) as multiple spatial information. Another importance of this task is to bridge the perceptual decision studies and object recognition, which will be expected to improve the understanding in either area. Using the main essence of this framework, we design our own experiment by applying more control on the spatial information resulting in a decision. In fact, this experiment design consists of both the single spatial information and multiple ones. This study aims to investigate the effect of each piece of spatial information on the decision individually, as well as to study the effect of combining this information on the decision. Consequently, this experiment design enables us to quantitatively predict the behavior of multiple informative trials from single ones. In particular, this research tends to study the combination and interaction of single information and their weights to address behavior in the presence of multiple spatial information in making a binary decision. This research hypothesizes that the perfect accumulator assumption might explain the integration of spatial information.MethodsHaving developed a customized algorithm, neutral human faces have been geometrically morphed such that 100% and +100% represent the first prototype, the second one, respectively. 0% morph depicts the middle face, which is half of the morph stream between the prototypes. The trials were designed to stimuli either have three informative features (eyes, mouth, nose simultaneously) or only one informative feature (eyes, mouth, and nose individually) fluctuating in time. These stimuli enabled us to control the featural information independently to study the impact of multiple spatial and temporal information in making the decision. The 3informative and 1informative trials were randomly interleaved in a block. Seven human subjects (2439 years old, four women) participated in this study with normal or correctedtonormal vision. All procedures were approved by the Ethics Committee of the Iran University of Medical Sciences. Stimuli were created and controlled in MATLAB and presented using routines from the psychophysics Toolbox extension. The subjects got familiar with the prototypes before taking part in the main experiment and also the structure of the task and its environment. After passing the training phases by reaching the required accuracy and speed, the participants were invited to the main phase of the experiment. They were instructed to maintain their gaze on the red fixation point in the center of the screen and report if the stimuli displayed on the side of the fixation point were more similar to the first prototype or the second one. Each participant completed a total of 1568 trials on average in eight blocks of 196 trials.ResultsLogistic regression analysis revealed that the subjects were not biased toward any of the choices. The reaction time decreased, and the probability of correct answers increased with the stimulus strength (morph %), showing that the subject confirmed their decision as expected based on the strength of perceived evidence. Another measure of the accumulation of evidence that this design of the experiment allowed us to compute was the psychophysical kernels for 0% morph trials. The positive amplitudes of the psychophysical kernels indicated that the decisions are made based on the integration of spatial information yet with unequal weight. Eyes weighed more for both 3featural, which is inconsistent with the previous findings for neutral faces and 1featural trials. The averages of psychophysical kernels amplitudes for onlynose and onlymouth trials were positive but not statistically significant, while these averages in 3featural trials were calculated statistically significant. This finding showed that the presence of eye information in 3featural trials intensified the extraction of information from nose and mouth in consistency with the reliability of the information in multiple sources of information studies. To quantify the contribution of each feature in the decision, we used logistic regression. The results showed that only linear coefficients relating to eye, nose, and mouth information have a statistically significant effect on the decision rather than multiplicative terms representing the interaction of features. The psychometric function and psychophysical kernels led us to use the integration model to predict the probability of corrects achieved in 3featural trials from the evidence calculated from the 1featural trials. To this end, the evidence contained in each oneinformative feature tria was calculated and linearly summed up with each other based on the regression model finding. Therefore, using the perfect linear accumulation assumption, we computed the expected accuracy from the result of 1informative feature trials to predict the accuracy in threeinformative feature trials. The present study showed that only considering the effective weight for each feature could extend the perfect accumulator assumption to explain the experimental accuracy for threeinformative feature trials.ConclusionThe present study #39;s findings suggest that the presence of multiple featural information simultaneously improved the extracting of information from less reliable features. This was shown by statistically significant weights of the nose and mouth in psychophysical kernels of 3informative feature trials compared to 1featural trials. Furthermore, the mechanism of perceptual decisionmaking in the presence of natural stimuli can be quantitatively explained by an extension of the perfect accumulator assumption by considering the informative featural weights. Considering the effective weight of each feature, the perfect accumulator assumption explains such a decisionmaking process in the presence of complex natural stimuli. This also might address the holistic effect quantitatively. Finally, taking advantage of perceptual decisionmaking findings can enhance our understanding of natural stimuli processing by paving the way for using neural imaging for further investigation of brain activities during such complex processes.Ethical ConsiderationsCompliance with ethical guidelinesThe present study consisted of experimental protocols approved by the Ethics Committee of the Iran University of Medical Sciences (IR.IUMS.REC.1399.1281). Written informed consent was obtained from all participants. The collected data would remain confidential and would be used only for scientific purposes. The participants were allowed to leave the experiment at any phase.Authors rsquo; contributionsHadiseh Hajimohammadi: conceptualization, data collection, analysis, visualization, writing original draft review, and editing. Sajjad Zabbah: conceptualization, supervision, writing review, and editing. Javad Hatami: Supervision, writingreview and editing. Reza Ebrahimpour: conceptualization, supervision, writing review, and editing.FundingThis study was funded by Iran Cognitive Sciences Technologies Council (9990). Data were recorded in the Cognitive Science Laboratory of Shahid Rajaee University.AcknowledgmentWe would like to thank all the participants in this study. The special thanks go to knowledgeable colleagues and open science for providing us helpful comments and technical supports where it was needed.Conflict of interestThe authors declare no conflicts of interest.