Simulations of Key Experiments

Research activities: Mental imagery

According to Kosslyn (1980, 1994), the mechanisms used to generate mental images are the same as those used in visual perception. The main difference between visual perception and mental imagery is the amount of detail in vision. Another difference is that we know that mental images are often created deliberately. If mental images do indeed operate in the same way as visual images, then one should expect that an imagined task should take about the same time as the task itself when carried out.

The tasks

First, think about the garden in the place where you live (or someone else’s that you know very well). Measure the time it takes to imagine walking from one end of the garden to the other. Don’t run or speed up the task but imagine yourself walking at a normal steady pace.

Next, think of an open space you know quite well, such as a local playing field. Measure the time it takes to imagine yourself walking in this field for about the same distance as you “walked” in the first task. Use one landmark in the field as the signal that you have covered the same distance as in the first task.

The third task is to measure the actual time it takes you to (physically) walk the length of the garden and back, and the fourth task is to measure the time it takes for you to walk the same distance in the field.

You should have four measurements. We will call them:

• Garden Imagery – the time taken for an imaginary walk down the garden.
• Garden Actual – the time taken for a real walk down the garden.
• Field Imagery – the time taken for an imaginary walk in a field.
• Field Actual – the time taken for a real walk in a field.

Dealing with the data

1. Calculate the ratio: Garden Imagery divided by Garden Actual. For example, suppose it took 40 seconds to image the walk and 60 seconds to do the walk, then you calculate 40/60, which is 0.667. Let’s call this value the Garden Ratio.
2. Calculate the ratio: Field Imagery divided by Field Actual. Let’s call this value the Field Ratio.

Kosslyn’s prediction

Since mental imagery and visual imagery exploit the same mechanisms, there are two predictions:

1. Both values should be close to 1.
2. The actual values of the Garden Ratio and the Field Ratio should be very similar to each other.

The explanation of these predictions is as follows. It should take about the same time to imagine the walks as to do them. This being the case, the computed ratios should be close to 1 (i.e., around 0.8 to 1.2). Imagining an activity should not be dependent on the detail of the imagined walk, but the actual distance. Therefore the two ratios should be about the same values.

However, it is likely that it took less time to imagine the walks as to do them, in which case your ratio values are likely to be less than 1 and closer to 0.5 or below. Furthermore, since a garden has more detail and hence more landmarks than an open field, it is likely that it took longer to imagine the walk in the garden than it did to imagine the walk in the field (since the latter has fewer landmarks). In this case, your Field Ratio is likely to be smaller than your Garden Ratio.

Ask yourself

1. Is mental imagery really like seeing with your eyes shut?
2. Why should there be any discrepancy between the time it takes for an imagined walk and the time the real walk takes?
3. Does everyone have mental images and do we use them in the same way?
4. How is that we can know whether we imagined something versus when we actually saw something?
5. Is it possible to measure mental imagery objectively?

References

Kosslyn, S.M. (1980). Image and mind. Cambridge, MA: Harvard University Press.

Kosslyn, S.M. (1994). Image and brain: The resolution of the imagery debate. Cambridge, MA: MIT Press.

Case Studies

Bruce and Young's (1986) model of face processing

Vuilleumier et al. (2005): Effects of perceived mutual gaze and gender on face processing and recognition memory

Bruce and Young (1986) described a model of face processing in which different aspects of face processing are carried out independently. This modular theory has been questioned in the literature, although there is supporting evidence for a number of these independent processes. The study by Vuilleumier et al. (2005) attempts to examine the effects of an individual's gaze on the ability to identify features of the face, such as the person's sex, and also on the ability to recognise the face afterwards.

The two main routes in the Bruce and Young model are processing an individual face for identity recognition (knowing who they are) and processing facial expression and features such as the sex, age and race of the face. If the two routes are independent then it should be possible to achieve one type of processing and fail at the other. This has been found with prosopagnosic patients, who can recognise the emotions in a face but not the identity of the face itself. Also, patients impaired at recognising an expression have been found to be able to recognise the face itself.

One important finding of Vuilleumier et al.'s (2005) study is that recognition of a set of new faces is influenced by facial expressiveness (the direction of gaze) and by features such as the sex of the face. This finding implies that the two routes are not completely independent and there is likely to be a good deal of interaction in processing between the two routes.

Perceived gaze is an interesting subject to study since it can convey important social information, such as the intentions and interests of others. These can further imply that an encounter is likely, and whether it might be positive (e.g., attraction) or negative (e.g., threat). Gender judgement is also something that individuals do rapidly and with a good deal of accuracy, even when cues such as facial hair, make-up and so on are removed from the decision process.

In the Vuilleumier et al. (2005) study there were two tasks. The participant was shown a number of faces and had to decide, by pressing one of two keys, whether the face was a man or a woman. The second task was a recognition task, in which the participant had to say whether each face was one of those used in the first task or not. The faces were presented either face-on or to the side, and with eyes looking at the viewer or looking away.

The results showed that the direction of gaze significantly affected the judgement of the sex of the face. Participants were quicker when the eyes were averted than when they were looking at the viewer. Also of interest was that this effect was especially so when the face was of the opposite sex to the participant. The results of the recognition task show that it was easier for faces looking directly at the viewer than for side-on faces and when the gaze was averted, and also especially for the opposite sex.

The conclusion is that perceived eye contact can interact with face processing and face recognition, even when gaze direction is not relevant to the task.

References

Bruce, V. & Young, A.W. (1986). Understanding face recognition. British Journal of Psychology, 77: 305–27.

Vuilleumier, P., George, N., Lister, V., Armony, J. & Driver, J. (2005). Effects of perceived mutual gaze and gender on face processing and recognition memory. Visual Cognition, 12(1): 85–101.

Flashcards

Multiple Choice Quiz