Thanks Clive for your reply.
'Memory/memories' are slightly odd terms. A person commonly speaks of 'my memories' as the '"pieces of mental video" that he stores in his 'memory', ie where 'memory' means the 'storage place in my brain". I'm not sure, but I think the former is the meaning that you intend. Is that right? I suggest this.
These observations suggest that the ability to access our memories changes depending on the particular situation, and is affected by the passage of time.
No, I am of the opinion that it should be the latter definition of memory, since it seems to relate more to the context of the sentence. I think the important thing is the access of information storage that is memory, not accessing of individual pieces of memory. I don't know if you agree with that though, and if it's debatable (I don't know if it's idiomatic to say 'our memories' in that context, overruling my reasoning). If the latter definition is used in your revised sentence, I come up with "These observations suggest that the ability to access our memory changes depending on the particular situation, and is affected by the passage of time." I only omitted the 's', and I think that's right(grammatically). In retrospect, I'd probably use "one's memory" rather than 'our memory' in keeping with the more formal tone of any thesis.
I prefer the singular, because it suggests to me 'all particular situations', whereas the plural sounds to me like 'some particular situations'.
Ok, I see. Would you still use 'depending on the particular situation'? I'm not sure why 'the' is needed, as it seems to imply to me that the particular situation is known, which is not; it is just any situation that is different than others.
Besides that, would you omit the ',' after 'changes'? I think it should be omitted because it slows down the pace of the sentence without making the sentence any clearer.