In psychological research, how a question is designed and structured or what method is used to collect information can impact the accuracy of the answers, thus biasing the obtained results. Up to now, self-assessment methods are broadly used in research on emotion for the collection of subjective affective ratings. Despite the increased adoption of psychophysiological measures for the inference of human affect, the field still relies extensively on self-reporting tools. For this reason, a common practice is to couple such measures to self-assessment scales or questionnaires.

Among these measures, the Self-Assessment Manikin (SAM) is one of the most diffused self-reporting scales, despite having been designed more than two decades ago.Recently, a number of experiments investigating human affective responses conducted at the SPECS laboratory at Pompeu Fabra University, highlighted the need for a more intuitive and modern tool for the self-assessment of emotion.

 Darwin experiments on Human emotion. Photographed by Duchenne de Boulogne (1868)

Given the necessity to use a more straightforward self-assessment tools, and the drive to contribute to the research field of human affect, the SPECS research group at the Centre of Autonomous Systems and Neurorobotics (N-RAS) of UPF led by ICREA professor Paul Verschure has designed a new digital scale for the self-assessment of emotion called the “Affective Slider” (AS)

Precisely, SPECS has designed a non-verbal digital scale, the Affective Slider, which, by using two separate slider controls, allows to collect self-reported ratings of pleasure and arousal in real-time.  

The Affective Slider (AS, left) is composed of two slider controls that measure basic emotions in terms of pleasure and arousal on a continuous scale that has been systematically calibrated to the well known Self-Assessment Manikin scale (SAM, right) in a number of experiments which involved emotional ratings.

To empirically validate the AS, leading author Dr. Alberto Betella conducted a systematic comparison between AS and SAM, in a task involving the emotional assessment of a series of images taken from the International Affective Picture System (IAPS), a standardized database containing pictures representing a wide range of semantic categories often used as a reference in psychological studies, which had been previously calibrated using SAM.

The purpose of this approach was twofold. On the one hand, Betella and Verschure’s goal was to systematically validate the AS as a reliable scale for the quick measurement of the affective dimensions of pleasure and arousal. On the other hand, the authors aimed to find whether the normative ratings provided with the original IAPS study from Lang et al. 1999, a benchmark in psychological research, could be replicated today.

The results of the study show that the AS can replace SAM in the self-reporting of pleasure and arousal

Dr. Betella designed an experiment where about 300 volunteers were asked to rate a set of pictures randomly selected from the International Affective Picture System (IAPS). The aim of the study was to empirically validate the AS by correlating the collected affective dimensions to the corresponding SAM ratings and to systematically compare new and normative IAPS ratings.

For the validation study, Dr. Betella collected more than 18 thousands single ratings. The collected scores were averaged, thus obtaining mean values of pleasure and arousal for both the AS and the SAM ratings associated with each of the IAPS stimuli. Results were obtained by comparing first the affective ratings between AS and SAM and finding correlations between the two scales. Second, by comparing the new collected SAM ratings to the normative SAM ratings provided with IAPS (S1 Data).

The results show a very strong correlation between the SAM and AS ratings, hence empirically demonstrating that the AS can replace SAM in the self-reporting of pleasure and arousal, with the additional advantages of being self-contained and easily reproducible in latest-generation digital devices

In contrast to SAM, the AS exploit new universal skills acquired through the large diffusion of modern electronic devices (e.g. interaction with interface elements such as sliders) and it does not require written instructions thus relying exclusively on non-verbal cues.

For these reasons, Betella and Verschure propose the AS is a more modern tool that can be used in experimental tasks that involve the self-reporting of pleasure and arousal and release it under an open license to be freely adopted by other researchers.

A second main outcome of this study is a significantly lower affective response to emotional stimuli. The authors, in fact, empirically show that people are getting more insensitive to highly arousing stimuli ranging from violence to sex

In addition, Betella and Verschure’s study highlights another remarkable outcome: the authors empirically demonstrated that IAPS pictures today are not as arousing as in the past. Their results clearly pinpoint to a desensitization towards arousing content, probably due to the mass exposure to media.

The implications of these findings for the field of affective science can be rather extensive given that a wide range of studies today still use the IAPS database to investigate affective behaviour response.

If researchers use the IAPS pictures along with their original ratings from the nineties, their results can be imprecise since those images, once rated as highly arousing, today are significantly less arousing.

In their paper Betella and Verschure have provided supplementary material with the new IAPS ratings as collected in 2015. Researcher using IAPS images today should use these more recent ratings, and not the old (normative) ones

Not only the author’s results demonstrate that legacy scales for the self-report of affect such as the SAM can be replaced with more intuitive measurement tools developed in accordance to modern design principles, but also – and most importantly - that affective responses might combine both invariant and variant components, suggesting a larger plasticity in emotional appraisal and expression than initially expected.

This raises the specific question to what extent human emotional experience and expression can be further moulded by experience in particular along the dimensions of pleasure and arousal.

REFERENCE

Betella,  A., Verschure,  P.F.M.J. (2016), “The Affective Slider: A Digital Self-Assessment Scale for the Measurement of Human Emotions”, PLoS ONE 11 (2): e0148037. doi:10.1371/journal.pone.0148037.This work was supported by European Research Council grant 341196 (CDAC).