one hour, the apes were presented with the choice of selecting hidden frozen juice, less-preferred grapes, or an empty platform. while the juice was the preferred item, it would melt before the hour. subjects were both male and female. food item placement was changed during multiple trials so that the study was not accidentally measuring familiarity. the primates rarely chose the empty platform, and after five minutes preferred the juice solution over the grape. after an hour, while a smaller number of primates chose the juice, the majority of apes still reached for melted juice. the study also wanted to compare human and primate performance on the task to show episodic memory. humans exhibit age-dependent performance with inverted u-shaped results, meaning ability increases in childhood, stabilizes for a few years and then descends as adulthood progresses. the similarities in findings found may indicate these primates and humans share some information encoding and storage mechanisms. future research may be done with a larger sample size and different experiments to replicate the inverted u-shape findings. rats rats demonstrate the ability to discriminate based on the what, where, and when components of episodic-like memory. a study by babb and crystal (2005) provided evidence that rats also demonstrate the ability to discriminate based on what, where, and when. in experiments using a radial arm maze, four of the eight arms of the maze contained food. the other arms were made inaccessible to the rats. of the food containing corridors of the maze, three contained standard rat-chow pellets while one arm contained high value chocolate-flavoured pellets. this was the first phase of the experiment, defined as the forced-choice phase (some corridors were inaccessible). the second phase was defined as the free-choice phase (all corridors were now accessible to the rats). the period of time between each phase served as a discriminating cue. some days the interval between phases would be short (30 minutes) other days the interval would be long (4 hours), but only one type of interval was tested each day. on days when a short interval was used, the previously inaccessible corridors were made accessible and were the only corridors to contain regular pellets and no chocolate pellets were refilled. on days using a long interval, pellets were refilled as on short interval days, but in addition, the chocolate pellets were refilled in the location they had originally been found. the rats were able to discriminate based on the length of interval before the test phase, with the phases following a long interval having the rats immediately search in the arm of the maze associated with the location of the high value (chocolate-flavoured) pellets. honey bees research suggests that honey bees possess circadian timed episodic-like memory. researchers in australia found what they consider to be circadian timed episodic-like memory in honey bees. in their study they examined foraging bees in three y-mazes. two mazes represented training and testing zones with different time placements. maze c acted as the location for transfer tests. the bees were placed in maze a in the afternoon hours of 2:30 to 5:30, whereas maze b held bees in the morning hours of 9:30 to 12:30. all of the three mazes had two compartments, and in mazes a and b, one held a sugar solution as a reward for making the positive decision. during training, the compartment containing the positive pattern was changed every thirty minutes. in maze a, the positive (rewarded) pattern was a blue horizontal pattern, while the negative (non-rewarded) pattern was a blue vertical pattern. additionally, the positive pattern for maze b was a yellow vertical (rewarded) pattern, with a yellow horizontal pattern as a negative (non-rewarded) pattern. the three aspects of episodic-like memory in this experiment are the morning or afternoon times (when), either maze a or b (where), and by using horizontal/vertical patterns (what). in the first of four experiments, the colour cue was removed by using black patterns, but the shape cues remained the same. the scientists tested whether the bees would still choose the positive pattern; this decision would then be based on the what, where, and when components. through the other three experiments, one of the cues was examined independently from the others. they found that, on average, 96% of bees learned to forage at each maze at the appropriate time. the experimenters suggest the error rate can be accounted for by a foraging strategy, in which multiple feeding locations are visited at fixed times. only a small number of bees visited the incorrect compartment during these times, and usually by only briefly hovered outside of it, instead of entering it. with the addition of visual pattern in this test, the bees also showed 80-88% of the time to have learned which maze to enter at the correct time. with the removal of the colour cue in both of these tests, the results remained consistent. the bees then showed they had learnt these rules by applying them to the new context, maze c, in experiment 2. in experiment 3, based on colour cue alone, having excluded the pattern and maze location cues, the forager bees could still make a correct decision. in the final experiment, the bees used only pattern orientation cues; the lowered performance showed how much more difficult this was than when the colour cue was still present. the researchers were uncertain, however, if the honey bees have a sense of time governed by their circadian rhythm by connecting a specific memory to a certain time period in the 24-hour cycle, or if they can measure elapsed time between two events. the difference in this type of memory from other episodic-like memory in animals is the presence of circadian timing, since normally interval timing is displayed. randolf menzel also provided evidence for episodic memory in honey bees by examining their learning of spatio-temporal tasks. the bees showed learning of serial positioning, turning serial patterns into episodes. the bees showed evidence of discrimination, thus at three out of four serial positions, stimuli were independently learned. menzel suggests strong results may be found by further isolating the configural components. such serial pattern configuration in mammals has been interpreted as indicative of mental representations of time and space. criticisms many criticisms surrounding episodic-like memory in animals revolve around the bischof-kohler hypothesis. the bischof-kohler hypothesis holds that only humans can dissociate themselves from their current motivation and take action for future needs. it suggests that animals are incapable of anticipating future needs, and any future-oriented behaviours they exhibit are either fixed action patterns or cued by their current motivational state. another criticism is that it is possible that in many cases animals are simply exhibiting garcia-type learning which involves conditioned taste aversion. this type of behavioural response occurs when a subject associates the taste of a food with negative symptoms caused by that food so that they will avoid consuming a possibly toxic substance in the future. this being said, if a scrub jay chooses one food over another preferred food that will eventually spoil this may not be planning for the future, but taste aversion to avoid getting sick from the spoiled food. suddendorf and busby have also specifically criticized the term episodic-like memory and believe it should be called www-memory (what-where-when memory) instead. they argued that an animal could know what happened, where it happened, and when it happened without actually being able to remember the specific event. likewise, personal memories are not always accurate. therefore, remembering a personal past event does not necessarily involve remembering the when and the where of the past event. areas for future research it has been argued that although behavioural criteria for mental time travel have been put forward and nonverbal tests have been proposed, current research has not yet provided a sufficient demonstration of mental time travel in animals that demonstrates flexibility. future research should focus on this component of episodic-like memory in order to demonstrate that animals are not only able to form what-where-when memories, but that they can bring together these components into an integrated framework and then modify this information later on. for future research, it has also been suggested that as we come across similarities between animal and human abilities we should immediately question how these abilities are dissimilar so that we do not mistake similarity for equivalence. while these strong criticisms do exist, however, many of the same critics are optimistic about future research. they suggest that a demonstration of this ability may be possible as long as researchers take these criticisms and alternative explanations into account.