Motion behind occluder: Amodal perception and visual motion extrapolation

ABSTRACT

One of the main challenges that our visual system must resolve is to judge the current position of an occluded moving object. This computation is known as motion extrapolation (ME), and it is required to perform several tasks: for example, judging when an occluded moving target collides with a given cue or whether it reappeared in time. These tasks may easily be encountered in more ecological settings, highlighting the importance of ME in our daily life. The goal of the current review is to synthesize the existing literature that investigated targets during occluded motion, in order to provide a general overview of the topic. To this aim, different aspects are discussed: occluded motion as a true perceptual phenomenon, the commonly used tasks in the literature, how perceptual and cognitive factors may affect individual performance, which mechanisms are supposed to be involved during ME and, finally, the neural correlates of occluded motion perception.

KEYWORDS:

• Occluded motion
• motion extrapolation
• prediction-motion
• time to contact
• amodal phase

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 In the supplementary material, some hints to be considered in occluded motion experiments can be found and some scripts are provided as examples of a PM experiment.

2 From now on, the literature about the amodal phase will be set aside, and the focus will be mostly on experiments involving motion extrapolation and PM (for more reading about the amodal phase, please see Flombaum et al., 2009). This was done for two reasons: first, it is impossible to cover in a single article the entire literature on this topic, and, second, we feel more qualified to discuss PM articles because our research mainly focused on this topic.

3 The role of eye movements in motion extrapolation tasks was also investigated with an accelerating object (Benguigui & Bennett, 2010; Bennett & Barnes, 2006; Bennett et al., 2007). However, in this review, only studies with target in uniform motion were considered.

4 Be aware that a dynamic mental simulation of a moving target is different from mental imagery. Makin (2018) do not consider mental imagery as a possible mechanism per se for ME. However, mental imagery may happen during occluded motion even without a direct instruction to imagine the moving target behind the occluder. However, we agree with Makin’s (2018) claim: a mechanism to guide imagery must be present and “ensure that it plays out at the right speed”.

5 The CNV is typically found using a chronometric paradigm in which there is an interval between the presentation of two stimuli, a warning stimulus followed by an imperative stimulus, which directs the observer to make a behavioural response. The CNV gradually builds up during the temporal interval between the two stimuli. In the TTC task the warning stimulus is the disappearance of the moving target behind the occluder, whereas the imperative stimulus corresponds to the estimated time to contact and the corresponding response to indicate so.

Additional information

Funding

The study was supported by a grant from MIUR (Dipartimenti di Eccellenza DM 11/05/2017 n.262) to the Department of General Psychology.