Title : Investigating visuospatial working memory for facial emotion and identity
Abstract:
The central executive plays a key role in the encoding of visual stimuli in working memory, including the memory for faces in a social context. Faces often contain important details about the identity of social targets as well as the emotion that these targets are expressing. Encoding accuracy requires that we have resources to consider and organize facial features into a holistic representation of a target. Of course, emotion recognition accuracy may be critical to encoding success. The cognitive demand on the participant when evaluating facial stimuli impacts emotion recognition accuracy and therefore the encoding of facial features and emotion categories. In the present study, load is operationalized in terms of a working memory task in which participants encode three stimuli successively on each trial, while simultaneously performing a secondary task that either is or is not resource demanding to the central executive. The load on the central executive affects memory for individual and bound features, including facial emotion, person identity, and the conjunction of the two. Participants completed either a standard visuospatial short-term memory task using images of objects that vary in terms of shape and/or color, or they completed a modified version of this task in which they were asked to encode emotion cues and/or identity cues in faces of social targets. Consistent with expectations, in the object-based working memory task, item memory was greater in the articulatory suppression condition that in the counting condition – a condition that imposed an additional load on the participants’ updating capacity. Moreover, the additional load in the counting condition elicited a strong recency effect favoring the last item in the memory set. However, this recency effect did not emerge in the articulatory suppression condition but just in the additional counting condition. Finally, when considering the load imposed on visuospatial working memory by the stimuli themselves regardless of the concurrent digit task, recency effects emerged favoring the final position in the memory set for both conditions involving memory for a single feature (shape or color) and for the conjunction condition (shape + color). For the face-based working memory task, memory was superior in the emotion + identity conjunction condition than in the emotion or identity conditions. This is an interesting finding given that observers have to integrate more features to perform the conjunction condition than the single feature conditions. The possible distinctiveness gained by stimuli if participants are presented with faces that differ from one another in two complex domains (i.e., identity and emotion) is further discussed. Also, the conjunction condition in the object-based working memory task did not yield the worst memory performance contrary to expectations. Parallels between the object-based and face-based working memory in the conjunction condition are also further discussed. Item memory was greater in the articulatory suppression condition than in the counting condition for the face-based working memory task as well. Recency effects emerged for the final position in the memory set under both articulatory suppression and additional counting conditions, but the recency effect was stronger in the additional counting condition here just as observed in the object-based working memory task. This is consistent with the expectation that additional counting served to disrupt the updating process and possibly caused relevant stimulus features for the first two items in the memory set to slip away. Finally, the largest recency effects in the face-based working memory task emerged when participants remembered the conjunction of the facial emotion and identity. Just as additional counting adds a load to the updating process in visuospatial working memory, so does the need to integrate multiple facial features. An incremental increase in performance with each later serial position supports the prediction that updating in visuospatial memory may increase the fragility of the memory trace of early items in the set when executive functioning is taxed by either feature integration or the need to update in a concurrent task.
Audience Take Away Notes:
- The findings of research in this area can be expanded to other clinical and age populations and their clinical outcomes on this task, as well as how the organizational structure of the brain plays a role in storage for objects and faces. Certain clinical populations, specifically Autism Spectrum Disorder and those with alexithymia (the inability to recognize and/or describe their own emotions), have difficulty recognizing and understanding emotion from others and also themselves. This could pose to be an issue that would hinder performance in the face-based working memory task and result in lower corrected recognition scores compared to the average population. Performance for clinical populations that are subject to neurodegenerative diseases could also be another route for future research. Alzheimer’s Disease, for example, is a progressive brain disease in which brain cell connections and the cells themselves slowly degenerate and die. As a result, past literature has found impairment for certain mental functions such as overall memory and even difficulty in recognizing certain emotions in others. A well-known symptom of Alzheimer’s Disease that occurs in the later stages of severe cognitive decline is the forgetting of family members, friends, and other loved ones. For patients with neurodegenerative diseases, high levels of corrected recognition could potentially be difficult to achieve in both the object-based and face-based working memory tasks. This would be a result of damage to the brain that affects binding and updating and, especially for the emotion trial block of the face-based task, the ability to recognize the emotions and identify them correctly when probed. The findings from such a study would be useful for recognizing and understanding how degeneration of the brain affects processes like facial emotion and person identity recognition, while also seeing if different areas of the brain function independently for the working memory storage of objects and faces.
- The observation of potential age differences would also be useful for other researchers to consider, especially in age comparison research. Age differences have been noted in emotion recognition research under a particular set of circumstances. However, considering that the current study is free of certain experimental techniques that can hinder performance for older adults (e.g., forced-choice task, serial presentation, and lack of verbal labels), the findings could further inform if there are any significant differences in the perceptual aspect of recognizing facial emotion and person identity, while ruling out any variance from the experimental design of added cognitive load. Until such a study is completed, the findings of the current study can be used as a guide for predicting how older adults would perform in this study.
- A significant takeaway from this is that the presence of an additional cognitive load negatively affects the first two items within a memory sequence, and this pattern was found for both objects and faces in the current study. The manipulation of the stimulus features for both the object-based and face-based working memory tasks infers that the capacity of the visuospatial working memory system is not as straight-forward as prior literature suggests. In this study, performance in the conjunction conditions were superior in the face-based working memory task, while the color condition was greatest in the object-based working memory task. This tells us that in contrast to objects, there is something about the integration of features for faces that improved memory performance for the last item in the memory sets when participants were presented with the facial stimuli sequentially. This could provide more insight as to how faces are encoded and stored in real-world environments and socially relevant contexts, as opposed to objects that lack necessary social meaning and context. This pattern also demonstrates how early items are still prone to displacement when the central executive is under cognitive load.
