When does repeated search in scenes involve memory? Looking at versus looking for objects in scenes

Abstract

One might assume that familiarity with a scene or previous encounters with objects embedded in a scene would benefit subsequent search for those items. However, in a series of experiments we show that this is not the case: When participants were asked to subsequently search for multiple objects in the same scene, search performance remained essentially unchanged over the course of searches despite increasing scene familiarity. Similarly, looking at target objects during previews, which included letter search, 30 seconds of free viewing, or even 30 seconds of memorizing a scene, also did not benefit search for the same objects later on. However, when the same object was searched for again memory for the previous search was capable of producing very substantial speeding of search despite many different intervening searches. This was especially the case when the previous search engagement had been active rather than supported by a cue. While these search benefits speak to the strength of memory-guided search when the same search target is repeated, the lack of memory guidance during initial object searches-despite previous encounters with the target objects-demonstrates the dominance of guidance by generic scene knowledge in real-world search.

Figure 1

A kitchen scene in which one might search for onions, baguettes, kitchen towels, etc.

Figure 2

Fifteen repeated searches through a single, unchanging display. Target words at the center of the display designated the object of search for each search.

Figure 3

Total response time, mean time to first target fixation, and decision time as a function of epoch for each block of Experiment One. Error bars are +/− 1 s.e.m. The y-axis covers 1000 msec in all three panels.

Figure 4

Response time for a target item as a function of the amount of time that target was incidentally fixated on previous trials.

Figure 5

An example of a search display used in Experiment 2, Block 0, consisting of 15 letters superimposed on the 15 search targets of Block 1 and Block 2. Note that we took care to ensure that letters were visible and did not completely cover target objects.

Figure 6

Response time, mean time to first target fixation, and decision time as a function of epoch for each block of Experiment Two. Note that Block 1 is the first block of object search. Block 1 from Exp. 1 is shown for comparison. Error bars are +/− 1 s.e.m.

Figure 7

Response time, mean time to first target fixation, and decision time as a function of epoch for each block of Experiment 3. Note that Block 1 is the first block of object search. Block 1 from Exp. 1 is shown for comparison. Error bars are +/− 1 s.e.m.

Figure 8

Mean RTs of 150 object searches in Block 1 plotted against mean gaze durations on 150 objects during the scene preview in Block 0. Objects of large sizes are depicted in red. Note the shade that was never looked at, but among the fastest to be found.

Figure 9

Response time, mean time to first target fixation, and decision time as a function of epoch for each block of Experiment Four. Note that Block 1 is the first block of object search. Block 1 from Exp 1. is shown for comparison. Error bars are +/− 1 s.e.m.

Figure 10

Mean RTs of 150 initial object searches in Block 1 plotted against mean gaze durations on 150 objects during the scene memorization in Block 0. Some objects of large sizes are depicted in red. Note that, as previously, the shade was rarely fixated incidentally, and was found relatively quickly.

Figure 11

Between-experiment correlation: Mean RTs of 150 initial object searches in Experiment 3 plotted against mean gaze durations on 150 objects during the scene memorization in Experiment 4. Again, objects of large sizes are depicted in red.

Figure 12

Response time as a function of block and of the type of experience (active search or target cued) in Block 0. Error bars are 1 s.e.m.

Figure 13

Gaze distributions of all observers during their initial search for a jam jar in Block 1 across Experiments 1–4. Note that despite different ways of previewing each scene in Experiments 2–4, gaze distributions are almost identical to initial searches in Experiment 1, where the scene was encountered for the first time.

Figure 14

Gaze distributions of all observers searching for a jam jar in Experiment 1. Search space substantially decreased from Block 1 over Block 2 to Block 3 (left to right).