Paper Presentation

1. LS4104 Cognition
Paper Presentation
Yeshma Ibrahim (16MS123)
Sachin Eldho (16MS051)

3. INTRODUCTION
➔ Domain General Intelligence (g) refers to the existence of a broad mental
capacity that influences performance on cognitive ability measures.
➔ Self control occurs when an organism waits for a more delayed, but better
outcome rather than taking a more immediate but less preferred outcome.
➔ Delay of gratification involves two components: delay choice (selecting a
delayed reward over an immediate one) and delay maintenance (sustaining
the decision to delay gratification even if the immediate reward is available).
➔ Sustained delay of gratification can be considered as a method of self control.
➔ Intertemporal choice is a choice made at one point of time which has an
influence in the possibilities at a later point of time.

4. INTRODUCTION
➔ Several previous studies have shown that general intelligence and
sustained delay of gratification are related in humans.
➔ Chimpanzees also delay gratification and have been tested for
general intelligence. But these two constructs have never been
compared in a non-human population.
➔ The results of this paper highlight that:
"Chimpanzees also show a strong relation between delayed
gratification and general intelligence.”

5. METHODS
★ Hybrid Delayed Task (HDT)
★ Primate Cognitive Test Battery (PCTB)
★ Quantification and Statistical Analysis

6. EXPERIMENTAL
SUBJECTS
Chimpanzee (Pan troglodytes)
➔ The subject population consists
of 40 adult chimpanzees (26
females and 14 males) of age
ranging from 18-48 years.
➔ Yerkes National Primate
Research Center and
Language Research Center
(LRC), Georgia State University

7. EXPERIMENTAL SETUP
● HDT trials were presented on a bench with a
mounted sliding tray.
● This bench was outside the enclosure where
the chimpanzee was kept.
● The chimpanzee could reach out through the
mesh of the enclosure to make the choices.
● The choices were two sets of discrete food
items (grape slices for Yerkes chimpanzees
and cereals for LRC chimpanzees).
● In both setups, though different, allowed
chimpanzees easily to retrieve their food items
during trials when they chose to do so.

8. Hybrid Delay Task (HDT)
➔ Choice Phase
● Chimpanzees are provided with two quantities of food items (randomized for left-
right placement) and are allowed to make an intertemporal choice.
➔ Accumulation Phase
● The experimenter removes the set which the chimpanzee did not choose.
● If the chimpanzee chooses the smaller quantity, the experimenter immediately
gives the items all at once. (smaller sooner or SS option)
● If the chimpanzee chooses the larger quantity, the experimenter gives them one at
a time at small intervals (larger later or LL option). This transfer of items continued
until all were delivered or until the chimpanzee began eating the items.

9. Hybrid Delay Task (HDT)
➔ 4 food items (grapes or cereals) in SS and 12 in LL
➔ Forced Trial: Only one set of food item is provided (either 4 or 12)
➔ Test Trial: Chimpanzee is allowed to choose between the two (4 and 12)
➔ Condition 1: Food items in LL given at intervals of 3 seconds (3s/item)
➔ Condition 2: Intervals of 10 seconds (10s/item)
➔ Condition 3: Intervals of 20 seconds (20s/item)
➔ All 40 chimpanzees completed five sessions of 8 trials (2 forced and 6 test
trials) of the first two conditions. But only 20 of them completed condition 3.

10. Primary Cognitive Test Battery (PCTB)
● Quantifies general and domain specific intelligence
● 13 Tasks: 9 measure physical cognition & 4 measure social cognition
● Measure spontaneous performance rather than trained performance
● Each chimpanzee is given two trials of PCTB in a two week interval
● g score calculation by Principal Axis Factor (PAF) analysis

11. Quantification & Statistical Analysis
➔ Principal Axis Factor (PAF) Analysis: To assess the relation of PCTB task
weighting and HDT performance. The output gives the relative weight that each
task in PCTB contribute to g score.
“PCTB tasks that load more strongly on the PAF g scores would be more strongly
associated with HDT performance than tasks that contribute less to the derived
measure of g.”
➔ Pearson Product Moment Correlation Coefficients (PPMCC): To assess the
relation between PAF g scores and the HDT measures.
➔ Multiple Regression Analysis & t Tests

12. RESULTS
➔ Performance of Each Chimpanzee in the HDT:
● The bars show the proportion of trials on which each
chimpanzee choose the LL option.
● The points indicate the mean number of items
obtained on those LL trials (maximum = 12).

13. RESULTS
➔ Relationship between
PCTB Scores and
HDT Performance
A) The percentage of
choice of the LL set.
B) Mean number of
items accumulated
when the LL set had
been selected.
C) HDT efficiency score

14. RESULTS
For the 3-s delay condition:
● correlation of PCTB score and proportion of LL choices made :
(r(38) = 0.57, p < 0.001).
● correlation of PCTB score and the average accumulation performance on LL trials :
(r(38) = 0.42, p < 0.001).
● correlation of PCTB score and efficiency score :
(r(38) = 0.65, p < 0.001).
On Multiple regression analysis, That analysis showed that the efficiency score best predicted
PCTB score (t(38) = 5.30, p < 0.001), and it accounted for 42.4% of the variance.

15. RESULTS
For the 10-s delay:
● correlation of PCTB score and proportion of LL choices made:
(r(38) = 0.60, p < 0.001).
● correlation of PCTB score and the average accumulation performance on LL trials :
(r(38) = 0.49, p < 0.001).
● Additionally, there was a significant correlation of PCTB score and efficiency score :
(r(38) = 0.63, p < 0.001).

16. RESULTS
For the 20-s delay:
● correlation of PCTB score and proportion of LL choices made:
(r(18) = 0.59, p < 0.001).
● correlation of PCTB score and the average accumulation performance on LL trials :
(r(18) = 0.54, p < 0.001).
● correlation of PCTB score and efficiency score :
(r(18) = 0.71, p < 0.001).

17. RESULTS
➔ The Relation between Weighted Score of each
PCTB Task and HDT Performance.

18. DISCUSSION : What can we infer from the results?
● Chimpanzee g is clearly and consistently related to self control capacities and
particularly to delay of gratification.
● Self control and intelligence are linked: same factors that most loaded on
chimpanzee g measures also best predicted performance on HDT.
● The Stanford Marshmallow Test (performed on humans)
● Is there something foundational about the role of inhibitory cognitive
processes in general intelligence??
● What can be inferred from this, from an evolutionary perspective??
● Can we argue for a strong selective pressure for cognitive processes that
relied on inhibitory control of actions??
● Or a precursor mechanisms in making intertemporal choices?

19. DISCUSSION : What can we infer from the results?
● It is worthy to note here again that it is the efficiency of the HDT performance
that had strong relations to Chimpanzee g scores.
● Efficiency DOES NOT differentiate between Chimpanzee choosing an LL or
an SS option!
● Rather, it gives importance to whether the subject is able to maintain the
delay, having chosen the LL option!!
● This occasional disengagement from Self Control was found in generally
more “intelligent chimpanzees”.
● THIS IS IMPORTANT!!
● Sometimes, choosing a less preferred, but more immediate option is
important as well!
● So, is this a sign of intelligent behaviour??

20. DISCUSSION : What can we infer from the results?
● The fact that there’s an association between g scores and HDT performance, forces us to question if
they have a similar or different GENETIC and NEURAL mechanisms underlying their expression.
● According to a recently reported research, acquisition of delay of gratification was associated with
increasing white matter connectivity between the striatum and the prefrontal cortex.
Can the volume of white matter tracts connecting these regions similarly be correlated with HDT
performance and g scores??
● There is a dearth of data determining the genetic correlation between general intelligence and HDT
performance in chimpanzees. Do you think common genes underlie their expression??
This is critical from an evolutionary perspective: Did the factors that selected for increased self
control had the collateral consequence of influencing the overall intelligence? Or is it the other way
round?Only genetic evidences could expound on this!

21. CONCLUSION
● More intelligent chimpanzees have better self control.
● More intelligent ones, waited when they decided to do so but also chose
for occasional immediate reward (Striking the right balance!!)
● Intelligence and Self control could have a neurobiological foundation
(unidentified)
● Importantly, these results demonstrate similarities between humans and
chimpanzees (with regard to self control behaviour and its relation to
general intelligence!!)