On 2017 Apr 07, Lydia Maniatis commented:

We can have an interesting conversation right here. Unless you clarify your assumptions, and properly control your variables and sample sizes,further research efforts will be wasted. Every difference in conscious experience is inevitably correlated with differences in physiology. The trick is in how you interpret the inevitable variations in the latter.(At this point in our understanding of brain function, I submit that such efforts are extremely premature.) In your case, you don't even seem to know what experience you are trying to correlate with brain activity.

I believe that your small stimulus duration and the fixation on the red spots may have biased the perception of figure to the corresponding surfaces in older viewers. You clearly don't have a alternative hypothesis that doesn't suffer from serious logical problems (as I noted in an earlier comment).

Peer reviewers are obviously not infallible, which is why this forum exists, and invoking them doesn't count as a counterargument.

On 2017 Apr 06, Jordan W Lass commented:

There are many interesting followups to our work indeed, some of which I believe merit further study. You have begun to identify some of these, and it seems to me there is the possibility for a constructive conversation to be had here. I highly encourage you to stop by our upcoming poster at the Vision Sciences Society conference in Florida in May, where we extend this work by exploring electrophysiological correlates of performance on this task in various conditions in both age groups. Our research group would be happy to discuss the issues you are taking with our work, as well as potentially-fruitful followups that can further address the questions we have raised in this work and that you have touched in some of the above comments.

I believe that, especially due to the presentation of this work over a number of conferences where I was challenged by experts in the field who helped me formulate and refine the ideas presented, as well as the rigorous peer review editorial process leading to the publication of this work in a high quality journal, the rational of our hypothesis and interpretation of our results are clearly laid out in the paper.

Thank you again for your keen interest in this work.

On 2017 Apr 06, Jordan W Lass commented:

None

On 2017 Apr 05, Lydia Maniatis commented:

You say that what you mean by “reduced ability to resolve figure-ground competition…is an open question.” But the language is clear, and regardless of whether concave or convex regions are seen as figure, the image is still being resolved into figure and ground. In other words, your experiments in no sense provide evidence that older people are not resolving images into figure and ground, only that convexity may not be as dispositive a factor as in younger people. Perhaps they are influenced more by the location of the red dot, as I believe that it is more likely that fixated regions will be seen as figure, all other things being equal.

In your response you specify that ‘failure to resolve’ may be interpreted in the sense of “decreased stability of the dominant percept and increased flipping.” However, in your discussion, you note, that, on the contrary, other researchers have found increased stability of the initial percept and difficulty in reversing ambiguous stimuli in older adults. If your inhibition explanation is consistent with BOTH increased flipping and greater stability, then it’s clearly too flexible to be testable. And, again, increased flipping rate is not really the same thing as “inability to resolve.”

The second alternative you propose is that stimuli are “not perceived to have figure ground character, perhaps being perceived as flat patterns.” This is obviously also in conflict with the other studies cited above. If the areas are perceived as adjacent rather than as having a figure-ground relationship, this also involves perceptual organization. For normal viewers, such a percept – e.g. simultaneously seeing both faces and vase in the Rubin vase, is very difficult, so it hard to imagine it occurring in older viewers, but who knows. If such an idea is testable, then you should test it.

You say the logic of your hypothesis is sound and your interpretations parsimonious, but in fact it isn’t clear what your hypothesis is, (what failure to resolve means). If your results are replicable, you may have demonstrated that, under the conditions of your experiment, convex region is less dispositive a factor in older adults. But in no sense have you properly formed or tested any explanatory hypotheses as to why this occurred.

In addition, I don’t think its fair to say that you’ve excluded the possible effect of the brevity of the stimulus. 250ms is still pretty short, considering that saccades typically take about 200ms to initiate. We know that older people generally respond more slowly at any task. The fact that practical considerations make it hard to work with longer exposure times doesn’t make this less of a problem.

On 2017 Apr 04, Jordan W Lass commented:

The interpretation that “differences in the ability to resolve the competition between alternative figure-ground interpretations of those stimuli" comes from the combination of results across experiments, and the literature on figure-ground and convexity context effects in specific. Given that we used a two-alternative forced choice paradigm, which has been commonly used to measure perception even when stimuli are presented below threshold, chance performance is P(convex=figure) = .5. Our observation was regressions to chance in the older group in both convexity bias and CCEs, which is consistent with the interpretation that the older group showed reduced ability to resolve figure-ground competition. Interestingly, as you may be getting at, what "reduced ability to resolve figure-ground" means is an open question: could it be decreased stability of the dominant percept and increased flipping between them or time spent in transition states? could it be that the stimuli are not perceived to have figure-ground character, perhaps being perceived as flat patterns? These are interesting questions indeed, which your idea of adding another response option "no figure-ground observed" is one way of addressing, although it comes with its own set of limitations.

Alternatively, as you propose, it may be the case that the older adults are resolving equally well as younger adults, but with increased tendency of perceiving concave figures compared to the younger group, which would also bring P(convex=figure) closer to .5. However, I can think of no literature or reasoning as to why that would be the case, so I see that as a less parsimonious interpretation. I am intrigued though, and if you are able to develop a hypothesis as to why this would be the case, it could make for an interesting experiment that might shed light into the nature of figure-ground organization in healthy aging.

Critically, the results of Experiment 4 showed a strong CCE in older adults when only concave regions were homogeneously coloured, which is a stimulus class that has been shown to be processed more quickly in younger adults (e.g., Salvagio and Peterson, 2012). Since no conCAVity-context effects were observed when only convex regions were homogeneously coloured (the opposite stimulus properties of the reduced competition stimuli), the Experiment 4 results are strongly supportive of the notion that older adults do show the CCE pattern well-characterized in younger adults, but that the high competition stimuli used in Experiment 1 are are particularly difficult for them to resolve.

The logic of our hypothesis is sound, and our interpretation is the most parsimonious we are aware of based on all the results. Thank you for your question, I would be happy to discuss further if you would like further clarification, or are interested in discussing some of these interesting followups.

On 2017 Apr 04, Lydia Maniatis commented:

If I’m reading this paper correctly, there’s a problem with the logic of the argument.

The finding is that older people are less likely than young people to see convex regions of a stimulus as figure. The authors say that this implies age “differences in the ability to resolve the competition between alternative figure-ground interpretations of those stimuli.”

However, the question they are asking in Exp’t1 is whether a red spot is seen as “on or off the region perceived as figure.” This implies that in every case, one of two border regions is seen as figure; at least, the authors don’t suggest that older people saw neither region as figure - and the question doesn’t allow for this possibility. So my question is, why doesn’t seeing the concave region as figure count as a resolution, inhibitory-competition-wise?

On 2017 Apr 04, Lydia Maniatis commented:

If I’m reading this paper correctly, there’s a problem with the logic of the argument.

The finding is that older people are less likely than young people to see convex regions of a stimulus as figure. The authors say that this implies age “differences in the ability to resolve the competition between alternative figure-ground interpretations of those stimuli.”

However, the question they are asking in Exp’t1 is whether a red spot is seen as “on or off the region perceived as figure.” This implies that in every case, one of two border regions is seen as figure; at least, the authors don’t suggest that older people saw neither region as figure - and the question doesn’t allow for this possibility. So my question is, why doesn’t seeing the concave region as figure count as a resolution, inhibitory-competition-wise?